CC(1)CC(1)NAME
cc, cc++ - GNU C and C++ Compiler
SYNOPSIScc [ option | filename ]...
cc++ [ option | filename ]...
DESCRIPTIONcc handles C, Objective-C, C++, and Objective-C++ source files. cc++
is not needed (but is still present for compatibility). cc processes
input files through one or more of four stages: preprocessing,
compilation, assembly, and linking. Source filename suffixes identify
the source language, but which name you use for the compiler governs
default assumptions:
cc assumes preprocessed (.i) files are C and assumes C style
linking.
cc++ assumes preprocessed (.ii) files are C++ and assumes C++ style
linking.
Suffixes of source file names indicate the language and kind of
processing to be done:
.c C source; preprocess, compile, assemble
.C C++ source; preprocess, compile, assemble
.cc C++ source; preprocess, compile, assemble
.cxx C++ source; preprocess, compile, assemble
.m Objective-C source; preprocess, compile, assemble
.M Objective-C++ source; preprocess, compile, assemble
.i preprocessed C; compile, assemble
.ii preprocessed C++; compile, assemble
.s Assembler source; assemble
.S Assembler source; preprocess, assemble
.h Preprocessor file; not usually named on command line
Files with other suffixes are passed to the linker. Common cases
include:
.o Object file
.a Archive file
Linking is always the last stage unless you use one of the -c, -S, or
-E options to avoid it (or unless compilation errors stop the whole
process). For the link stage, all .o files corresponding to source
files, -l libraries, unrecognized filenames (including named .o object
files and .a archives) are passed to the linker in command-line order.
cc has been substantially modified and extended by NeXT Computer, Inc.
to support the use of Objective-C, Objective-C++, and Mach. For
documentation, see the NeXT Developer's Library (accessible through the
NeXT Developer target of the Digital Librarian).
OPTIONS
Options must be separate: `-dr' is quite different from `-d -r '.
Most `-f' and `-W' options have two contrary forms: -fname and
-fno-name (or -Wname and -Wno-name). Only the non-default forms are
shown here.
Here is a summary of all the options, grouped by type. Explanations
are in the following sections.
Overall Options
-c -S -E -o file -pipe -v -x language
Language Options
-ansi -fall-virtual -fcond-mismatch -fdollars-in-identifiers
-fenum-int-equiv -fexternal-templates -fno-asm -fno-builtin
-fno-strict-prototype -fsigned-bitfields -fsigned-char
-fthis-is-variable -funsigned-bitfields -funsigned-char
-fwritable-strings -traditional -traditional-cpp -trigraphs
-ObjC -ObjC++ -posix -posixstrict
Warning Options
-fsyntax-only -pedantic -pedantic-errors -w -W -Wall
-Waggregate-return -Wcast-align -Wcast-qual -Wchar-subscript
-Wcomment -Wconversion -Wenum-clash -Werror -Wformat
-Wid-clash-len -Wimplicit -Winline -Wmissing-prototypes
-Wnested-externs -Wno-import -Wparentheses -Wpointer-arith
-Wredundant-decls -Wreturn-type -Wshadow -Wstrict-prototypes
-Wswitch -Wtemplate-debugging -Wtraditional -Wtrigraphs
-Wuninitialized -Wunused -Wwrite-strings -Wprecomp -Wno-precomp
Debugging Options
-a -dletters -fpretend-float -g -glevel -ggdb -p -pg -save-temps
-print-libgcc-file-name
Optimization Options
-fcaller-saves -fcse-follow-jumps -fcse-skip-blocks
-fdelayed-branch -felide-constructors -fexpensive-optimizations
-ffast-math -ffloat-store -fforce-addr -fforce-mem
-finline-functions -fkeep-inline-functions -fmemoize-lookups
-fno-default-inline -fno-defer-pop -fno-function-cse -fno-inline
-fno-peephole -fomit-frame-pointer -frerun-cse-after-loop
-fschedule-insns -fschedule-insns2 -fstrength-reduce
-fthread-jumps -funroll-all-loops -funroll-loops -O -O2
Preprocessor Options
-Aassertion -C -dD -dM -dN -Dmacro[=defn] -E -H -idirafter dir
-include file -imacros file -iprefix file -iwithprefix dir -M
-MD -MM -MMD -nostdinc -P -Umacro -undef -precomp -no-precomp
Assembler Option
-Wa,option
Linker Options
-llibrary -nostartfiles -nostdlib -shared -symbolic
-Xlinker option -Wl,option -u symbol
Directory Options
-Bprefix -Idir -I- -Ldir
Target Options
-b machine -V version
Configuration Dependent Options
M680x0 Options
-m68000 -m68020 -m68020-40 -m68030 -m68040 -m68881 -mbitfield
-mc68000 -mc68020 -mfpa -mnobitfield -mrtd -mshort -msoft-float
i386 Options
-m486 -mno-486 -msoft-float -mno-fp-ret-in-387
HPPA Options
-mpa-risc-1-0 -mpa-risc-1-1 -mkernel -mshared-libs
-mno-shared-libs -mlong-calls -mdisable-fpregs
-mdisable-indexing -mtrailing-colon
Code Generation Options
-fcall-saved-reg -fcall-used-reg -ffixed-reg
-finhibit-size-directive -fnonnull-objects -fno-common
-fno-gnu-linker -fpcc-struct-return -freg-struct-returno
-fshared-data -fshort-enums -fshort-double -fvolatile
-fvolatile-global -fverbose-asm
OVERALL OPTIONS-x language
Specify explicitly the language for the following input files
(rather than choosing a default based on the file name suffix) .
This option applies to all following input files until the next
`-x' option. Possible values of language are `c',
`objective-c', `c-header', `c++', `cpp-output', `assembler', and
`assembler-with-cpp'.
-x none
Turn off any specification of a language, so that subsequent
files are handled according to their file name suffixes (as they
are if `-x' has not been used at all).
If you want only some of the four stages (preprocess, compile,
assemble, link), you can use `-x' (or filename suffixes) to tell cc
where to start, and one of the options `-c', `-S', or `-E' to tell
where cc to stop. Note that some combinations (for example, `-x
cpp-output -E') instruct cc to do nothing at all.
-c Compile or assemble the source files, but do not link. The
compiler output is an object file corresponding to each source
file.
By default, cc makes the object file name for a source file by
replacing the suffix `.c', `.i', `.s', etc., with `.o'. Use -o
to select another name.
cc ignores any unrecognized input files (those that do not
require compilation or assembly) with the -c option.
-S Stop after the stage of compilation proper; do not assemble.
The output is an assembler code file for each non-assembler
input file specified.
By default, cc makes the assembler file name for a source file
by replacing the suffix `.c', `.i', etc., with `.s'. Use -o to
select another name.
cc ignores any input files that don't require compilation.
-E Stop after the preprocessing stage; do not run the compiler
proper. The output is preprocessed source code, which is sent
to the standard output.
cc ignores input files which don't require preprocessing.
-o file
Place output in file file. This applies regardless to whatever
sort of output cc produces, whether it be an executable file, an
object file, an assembler file or preprocessed C code.
Since only one output file can be specified, it does not make
sense to use `-o' when compiling more than one input file,
unless you are producing an executable file as output.
If you do not specify `-o', the default is to put an executable
file in `a.out', the object file for `source.suffix' in
`source.o', its assembler file in `source.s', and all
preprocessed C source on standard output.
-v Print (on standard error output) the commands executed to run
the stages of compilation. Also print the version number of the
compiler driver program and of the preprocessor and the compiler
proper.
-pipe Use pipes rather than temporary files for communication between
the various stages of compilation. This fails to work on some
systems where the assembler cannot read from a pipe; but the GNU
assembler has no trouble.
LANGUAGE OPTIONS
The following options control the dialect of C that the compiler
accepts:
-ansi Support all ANSI standard C programs.
This turns off certain features of cc that are incompatible with
ANSI C, such as the asm, inline and typeof keywords, and
predefined macros such as unix and vax that identify the type of
system you are using. It also enables the undesirable and
rarely used ANSI trigraph feature, and disallows `$' as part of
identifiers.
The alternate keywords __asm__, __extension__, __inline__ and
__typeof__ continue to work despite `-ansi'. You would not want
to use them in an ANSI C program, of course, but it is useful to
put them in header files that might be included in compilations
done with `-ansi'. Alternate predefined macros such as __unix__
and __vax__ are also available, with or without `-ansi'.
The `-ansi' option does not cause non-ANSI programs to be
rejected gratuitously. For that, `-pedantic' is required in
addition to `-ansi'.
The preprocessor predefines a macro __STRICT_ANSI__ when you use
the `-ansi' option. Some header files may notice this macro and
refrain from declaring certain functions or defining certain
macros that the ANSI standard doesn't call for; this is to avoid
interfering with any programs that might use these names for
other things.
-fno-asm
Do not recognize asm, inline or typeof as a keyword. These
words may then be used as identifiers. You can use __asm__,
__inline__ and __typeof__ instead. `-ansi' implies `-fno-asm'.
-fno-builtin
Don't recognize built-in functions that do not begin with two
leading underscores. Currently, the functions affected include
_exit, abort, abs, alloca, cos, exit, fabs, labs, memcmp,
memcpy, sin, sqrt, strcmp, strcpy, and strlen.
The `-ansi' option prevents alloca and _exit from being builtin
functions.
-fno-strict-prototype
Treat a function declaration with no arguments, such as `int foo
();', as C would treat it—as saying nothing about the number of
arguments or their types (C++ only). Normally, such a
declaration in C++ means that the function foo takes no
arguments.
-trigraphs
Support ANSI C trigraphs. The `-ansi' option implies
`-trigraphs'.
-traditional
Attempt to support some aspects of traditional C compilers. For
details, see the GNU C Manual; the duplicate list here has been
deleted so that we won't get complaints when it is out of date.
But one note about C++ programs only (not C). `-traditional'
has one additional effect for C++: assignment to this is
permitted. This is the same as the effect of
`-fthis-is-variable'.
-traditional-cpp
Use the regular GNU preprocessor rather than the
NEXTSTEP-specific cpp-precomp option. Precompiled headers are
not supported when `-traditional-cpp' is used.
-fdollars-in-identifiers
Permit the use of `$' in identifiers (C++ only). You can also
use `-fno-dollars-in-identifiers' to explicitly prohibit use of
`$'. (cc++ allows `$' by default on some target systems but not
others.)
-fenum-int-equiv
Permit implicit conversion of int to enumeration types (C++
only). Normally cc++ allows conversion of enum to int, but not
the other way around.
-fexternal-templates
Produce smaller code for template declarations, by generating
only a single copy of each template function where it is defined
(C++ only). To use this option successfully, you must also mark
all files that use templates with either `#pragma
implementation' (the definition) or `#pragma interface'
(declarations).
When your code is compiled with `-fexternal-templates', all
template instantiations are external. You must arrange for all
necessary instantiations to appear in the implementation file;
you can do this with a typedef that references each
instantiation needed. Conversely, when you compile using the
default option `-fno-external-templates', all template
instantiations are explicitly internal.
-fall-virtual
Treat all possible member functions as virtual, implicitly. All
member functions (except for constructor functions and new or
delete member operators) are treated as virtual functions of the
class where they appear.
This does not mean that all calls to these member functions will
be made through the internal table of virtual functions. Under
some circumstances, the compiler can determine that a call to a
given virtual function can be made directly; in these cases the
calls are direct in any case.
-fcond-mismatch
Allow conditional expressions with mismatched types in the
second and third arguments. The value of such an expression is
void.
-fthis-is-variable
Permit assignment to this (C++ only). The incorporation of
user-defined free store management into C++ has made assignment
to `this' an anachronism. Therefore, by default it is invalid
to assign to this within a class member function. However, for
backwards compatibility, you can make it valid with `-fthis-is-
variable'.
-funsigned-char
Let the type char be unsigned, like unsigned char.
Each kind of machine has a default for what char should be. It
is either like unsigned char by default or like signed char by
default.
Ideally, a portable program should always use signed char or
unsigned char when it depends on the signedness of an object.
But many programs have been written to use plain char and expect
it to be signed, or expect it to be unsigned, depending on the
machines they were written for. This option, and its inverse,
let you make such a program work with the opposite default.
The type char is always a distinct type from each of signed char
and unsigned char, even though its behavior is always just like
one of those two.
-fsigned-char
Let the type char be signed, like signed char.
Note that this is equivalent to `-fno-unsigned-char', which is
the negative form of `-funsigned-char'. Likewise,
`-fno-signed-char' is equivalent to `-funsigned-char'.
-fsigned-bitfields
-funsigned-bitfields
-fno-signed-bitfields
-fno-unsigned-bitfields
These options control whether a bitfield is signed or unsigned,
when declared with no explicit `signed' or `unsigned' qualifier.
By default, such a bitfield is signed, because this is
consistent: the basic integer types such as int are signed
types.
However, when you specify `-traditional', bitfields are all
unsigned no matter what.
-fwritable-strings
Store string constants in the writable data segment and don't
uniquize them. This is for compatibility with old programs
which assume they can write into string constants.
`-traditional' also has this effect.
Writing into string constants is a very bad idea; “constants”
should be constant.
-ObjC Specify that the file should be compiled as an Objective-C
source program.
-ObjC++
Specify that the file should be compiled as an Objective-C++
source program.
-posix Specify that the file should be compiled as a POSIX 1003.1
conforming source program. Note that POSIX kernel interfaces are
not supported for NEXTSTEP applications. The POSIX kernal
interfaces are supported only for C source files.
-posixstrict
Specify that the file should be compiled as a strict POSIX
1003.1 conforming source program without optional features. Note
that POSIX kernel interfaces are not supported for NEXTSTEP
applications. The POSIX kernal interfaces are supported only for
C source files.
PREPROCESSOR OPTIONS
These options control the C preprocessor, which is run on each C source
file before actual compilation.
If you use the `-E' option, cc does nothing except preprocessing. Some
of these options make sense only together with `-E' because they cause
the preprocessor output to be unsuitable for actual compilation.
-include file
Process file as input before processing the regular input file.
In effect, the contents of file are compiled first. Any `-D'
and `-U' options on the command line are always processed before
`-include file', regardless of the order in which they are
written. All the `-include' and `-imacros' options are
processed in the order in which they are written.
-imacros file
Process file as input, discarding the resulting output, before
processing the regular input file. Because the output generated
from file is discarded, the only effect of `-imacros file' is to
make the macros defined in file available for use in the main
input. The preprocessor evaluates any `-D' and `-U' options on
the command line before processing `-imacrosfile', regardless of
the order in which they are written. All the `-include' and
`-imacros' options are processed in the order in which they are
written.
-idirafter dir
Add the directory dir to the second include path. The
directories on the second include path are searched when a
header file is not found in any of the directories in the main
include path (the one that `-I' adds to).
-iprefix prefix
Specify prefix as the prefix for subsequent `-iwithprefix'
options.
-iwithprefix dir
Add a directory to the second include path. The directory's
name is made by concatenating prefix and dir, where prefix was
specified previously with `-iprefix'.
-nostdinc
Do not search the standard system directories for header files.
Only the directories you have specified with `-I' options (and
the current directory, if appropriate) are searched.
By using both `-nostdinc' and `-I-', you can limit the include-
file search file to only those directories you specify
explicitly.
-nostdinc++
Do not search for header files in the C++-specific standard
directories, but do still search the other standard directories.
(This option is used when building `libg++'.)
-undef Do not predefine any nonstandard macros. (Including
architecture flags).
-E Run only the C preprocessor. Preprocess all the C source files
specified and output the results to standard output or to the
specified output file.
-C Tell the preprocessor not to discard comments. Used with the
`-E' option.
-P Tell the preprocessor not to generate `#line' commands. Used
with the `-E' option.
-M Tell the preprocessor to output a rule suitable for make
describing the dependencies of each object file. For each
source file, the preprocessor outputs one make-rule whose target
is the object file name for that source file and whose
dependencies are all the files `#include'd in it. This rule may
be a single line or may be continued with `\'-newline if it is
long. The list of rules is printed on standard output instead
of the preprocessed C program.
`-M' implies `-E'.
-MM Like `-M' but the output mentions only the user header files
included with `#include file"'. System header files included
with `#include <file>' are omitted.
-MD Like `-M' but the dependency information is written to files
with names made by replacing `.o' with `.d' at the end of the
output file names. This is in addition to compiling the file as
specified—`-MD' does not inhibit ordinary compilation the way
`-M' does.
The Mach utility `md' can be used to merge the `.d' files into a
single dependency file suitable for using with the `make'
command.
-MMD Like `-MD' except mention only user header files, not system
header files.
-H Print the name of each header file used, in addition to other
normal activities.
-Aquestion(answer)
Assert the answer answer for question, in case it is tested with
a preprocessor conditional such as `#if #question(answer)'.
`-A-' disables the standard assertions that normally describe
the target machine.
-Aquestion
(answer) Assert the answer answer for question, in case it is
tested with a preprocessor conditional such as `#if
#question(answer)'. `-A-' disables the standard assertions that
normally describe the target machine.
-Dmacro
Define macro macro with the string `1' as its definition.
-Dmacro=defn
Define macro macro as defn. All instances of `-D' on the
command line are processed before any `-U' options.
-Umacro
Undefine macro macro. `-U' options are evaluated after all `-D'
options, but before any `-include' and `-imacros' options.
-dM Tell the preprocessor to output only a list of the macro
definitions that are in effect at the end of preprocessing.
Used with the `-E' option.
-dD Tell the preprocessor to pass all macro definitions into the
output, in their proper sequence in the rest of the output.
-dN Like `-dD' except that the macro arguments and contents are
omitted. Only `#define name' is included in the output.
-precomp
Produce a precompiled header.
-no-precomp
Do not use precompiled headers.
ASSEMBLER OPTION
-Wa,option
Pass option as an option to the assembler. If option contains
commas, it is split into multiple options at the commas.
LINKER OPTIONS
These options come into play when the compiler links object files into
an executable output file. They are meaningless if the compiler is not
doing a link step.
object-file-name
A file name that does not end in a special recognized suffix is
considered to name an object file or library. (Object files are
distinguished from libraries by the linker according to the file
contents.) If cc does a link step, these object files are used
as input to the linker.
-llibrary
Use the library named library when linking.
The linker searches a standard list of directories for the
library, which is actually a file named `liblibrary.a'. The
linker then uses this file as if it had been specified precisely
by name.
The directories searched include several standard system
directories plus any that you specify with `-L'.
Normally the files found this way are library files—archive
files whose members are object files. The linker handles an
archive file by scanning through it for members which define
symbols that have so far been referenced but not defined.
However, if the linker finds an ordinary object file rather than
a library, the object file is linked in the usual fashion. The
only difference between using an `-l' option and specifying a
file name is that `-l' surrounds library with `lib' and `.a' and
searches several directories.
-nostartfiles
Do not use the standard system startup files when linking. The
standard libraries are used normally.
-nostdlib
Don't use the standard system libraries and startup files when
linking. Only the files you specify will be passed to the
linker.
-shared
Produce a shared object which can then be linked with other
objects to form an executable. Only a few systems support this
option.
-symbolic
Bind references to global symbols when building a shared object.
Warn about any unresolved references (unless overridden by the
link editor option `-Xlinker -z -Xlinker defs'). Only a few
systems support this option.
-Xlinker option
Pass option as an option to the linker. You can use this to
supply system-specific linker options which cc does not know how
to recognize.
If you want to pass an option that takes an argument, you must
use `-Xlinker' twice, once for the option and once for the
argument. For example, to pass `-assert definitions', you must
write `-Xlinker -assert -Xlinker definitions'. It does not work
to write `-Xlinker "-assert definitions"', because this passes
the entire string as a single argument, which is not what the
linker expects.
-Wl,option
Pass option as an option to the linker. If option contains
commas, it is split into multiple options at the commas.
-u symbol
Pretend the symbol symbol is undefined, to force linking of
library modules to define it. You can use `-u' multiple times
with different symbols to force loading of additional library
modules.
DIRECTORY OPTIONS
These options specify directories to search for header files, for
libraries and for parts of the compiler:
-Idir Append directory dir to the list of directories searched for
include files.
-I- Any directories you specify with `-I' options before the `-I-'
option are searched only for the case of `#include "file"'; they
are not searched for `#include <file>'.
If additional directories are specified with `-I' options after
the `-I-', these directories are searched for all `#include'
directives. (Ordinarily all `-I' directories are used this
way.)
In addition, the `-I-' option inhibits the use of the current
directory (where the current input file came from) as the first
search directory for `#include "file"'. There is no way to
override this effect of `-I-'. With `-I.' you can specify
searching the directory which was current when the compiler was
invoked. That is not exactly the same as what the preprocessor
does by default, but it is often satisfactory.
`-I-' does not inhibit the use of the standard system
directories for header files. Thus, `-I-' and `-nostdinc' are
independent.
-Ldir Add directory dir to the list of directories to be searched for
`-l'.
-Bprefix
This option specifies where to find the executables, libraries
and data files of the compiler itself.
The compiler driver program runs one or more of the subprograms
`cpp', `cc1obj' (or, for C++, `cc1objplus'), `as' and `ld'. It
tries prefix as a prefix for each program it tries to run, both
with and without `machine/version/'.
For each subprogram to be run, the compiler driver first tries
the `-B' prefix, if any. If that name is not found, or if `-B'
was not specified, the driver tries the directory `libarch/'.
Otherwise, the compiler driver searches for the unmodified
program name, using the directories specified in your `PATH'
environment variable.
You can get a similar result from the environment variable
GCC_EXEC_PREFIX; if it is defined, its value is used as a prefix
in the same way. If both the `-B' option and the
GCC_EXEC_PREFIX variable are present, the `-B' option is used
first and the environment variable value second.
WARNING OPTIONS
Warnings are diagnostic messages that report constructions which are
not inherently erroneous but which are risky or suggest there may have
been an error.
These options control the amount and kinds of warnings produced by cc:
-fsyntax-only
Check the code for syntax errors, but don't emit any output.
-w Inhibit all warning messages.
-Wno-import
Inhibit warning messages about the use of #import.
-pedantic
Issue all the warnings demanded by strict ANSI standard C;
reject all programs that use forbidden extensions.
Valid ANSI standard C programs should compile properly with or
without this option (though a rare few will require `-ansi').
However, without this option, certain GNU extensions and
traditional C features are supported as well. With this option,
they are rejected. There is no reason to use this option; it
exists only to satisfy pedants.
`-pedantic' does not cause warning messages for use of the
alternate keywords whose names begin and end with `__'.
Pedantic warnings are also disabled in the expression that
follows __extension__. However, only system header files should
use these escape routes; application programs should avoid them.
-pedantic-errors
Like `-pedantic', except that errors are produced rather than
warnings.
-W Print extra warning messages for these events:
· A nonvolatile automatic variable might be changed by a call to
longjmp. These warnings are possible only in optimizing
compilation.
The compiler sees only the calls to setjmp. It cannot know
where longjmp will be called; in fact, a signal handler could
call it at any point in the code. As a result, you may get a
warning even when there is in fact no problem because longjmp
cannot in fact be called at the place which would cause a
problem.
· A function can return either with or without a value. (Falling
off the end of the function body is considered returning without
a value.) For example, this function would evoke such a
warning:
foo (a)
{
if (a > 0)
return a;
}
Spurious warnings can occur because cc does not realize that
certain functions (including abort and longjmp) will never
return.
· An expression-statement contains no side effects.
· An unsigned value is compared against zero with `>' or `<='.
-Wimplicit
Warn whenever a function or parameter is implicitly declared.
-Wreturn-type
Warn whenever a function is defined with a return-type that
defaults to int. Also warn about any return statement with no
return-value in a function whose return-type is not void.
-Wunused
Warn whenever a local variable is unused aside from its
declaration, whenever a function is declared static but never
defined, and whenever a statement computes a result that is
explicitly not used.
-Wswitch
Warn whenever a switch statement has an index of enumeral type
and lacks a case for one or more of the named codes of that
enumeration. (The presence of a default label prevents this
warning.) case labels outside the enumeration range also
provoke warnings when this option is used.
-Wcomment
Warn whenever a comment-start sequence `/∗' appears in a
comment.
-Wtrigraphs
Warn if any trigraphs are encountered (assuming they are
enabled).
-Wformat
Check calls to printf and scanf, etc., to make sure that the
arguments supplied have types appropriate to the format string
specified.
-Wchar-subscripts
Warn if an array subscript has type char. This is a common
cause of error, as programmers often forget that this type is
signed on some machines.
-Wuninitialized
An automatic variable is used without first being initialized.
These warnings are possible only in optimizing compilation,
because they require data flow information that is computed only
when optimizing. If you don't specify `-O', you simply won't
get these warnings.
These warnings occur only for variables that are candidates for
register allocation. Therefore, they do not occur for a
variable that is declared volatile, or whose address is taken,
or whose size is other than 1, 2, 4 or 8 bytes. Also, they do
not occur for structures, unions or arrays, even when they are
in registers.
Note that there may be no warning about a variable that is used
only to compute a value that itself is never used, because such
computations may be deleted by data flow analysis before the
warnings are printed.
These warnings are made optional because cc is not smart enough
to see all the reasons why the code might be correct despite
appearing to have an error. Here is one example of how this can
happen:
{
int x;
switch (y)
{
case 1: x = 1;
break;
case 2: x = 4;
break;
case 3: x = 5;
}
foo (x);
}
If the value of y is always 1, 2 or 3, then x is always
initialized, but cc doesn't know this. Here is another common
case:
{
int save_y;
if (change_y) save_y = y, y = new_y;
...
if (change_y) y = save_y;
}
This has no bug because save_y is used only if it is set.
Some spurious warnings can be avoided if you declare as volatile
all the functions you use that never return.
-Wparentheses
Warn if parentheses are omitted in certain contexts.
-Wtemplate-debugging
When using templates in a C++ program, warn if debugging is not
yet fully available (C++ only).
-Wall All of the above `-W' options combined. These are all the
options which pertain to usage that we recommend avoiding and
that we believe is easy to avoid, even in conjunction with
macros.
The remaining `-W...' options are not implied by `-Wall' because they
warn about constructions that we consider reasonable to use, on
occasion, in clean programs.
-Wtraditional
Warn about certain constructs that behave differently in
traditional and ANSI C.
· Macro arguments occurring within string constants in the macro
body. These would substitute the argument in traditional C, but
are part of the constant in ANSI C.
· A function declared external in one block and then used after
the end of the block.
· A switch statement has an operand of type long.
-Wshadow
Warn whenever a local variable shadows another local variable.
-Wid-clash-len
Warn whenever two distinct identifiers match in the first len
characters. This may help you prepare a program that will
compile with certain obsolete, brain-damaged compilers.
-Wpointer-arith
Warn about anything that depends on the “size of” a function
type or of void. cc assigns these types a size of 1, for
convenience in calculations with void ∗ pointers and pointers to
functions.
-Wcast-qual
Warn whenever a pointer is cast so as to remove a type qualifier
from the target type. For example, warn if a const char ∗ is
cast to an ordinary char ∗.
-Wcast-align
Warn whenever a pointer is cast such that the required alignment
of the target is increased. For example, warn if a char ∗ is
cast to an int ∗ on machines where integers can only be accessed
at two- or four-byte boundaries.
-Wwrite-strings
Give string constants the type const char[length] so that
copying the address of one into a non-const char ∗ pointer will
get a warning. These warnings will help you find at compile
time code that can try to write into a string constant, but only
if you have been very careful about using const in declarations
and prototypes. Otherwise, it will just be a nuisance; this is
why we did not make `-Wall' request these warnings.
-Wconversion
Warn if a prototype causes a type conversion that is different
from what would happen to the same argument in the absence of a
prototype. This includes conversions of fixed point to floating
and vice versa, and conversions changing the width or signedness
of a fixed point argument except when the same as the default
promotion.
-Waggregate-return
Warn if any functions that return structures or unions are
defined or called. (In languages where you can return an array,
this also elicits a warning.)
-Wstrict-prototypes
Warn if a function is declared or defined without specifying the
argument types. (An old-style function definition is permitted
without a warning if preceded by a declaration which specifies
the argument types.)
-Wmissing-prototypes
Warn if a global function is defined without a previous
prototype declaration. This warning is issued even if the
definition itself provides a prototype. The aim is to detect
global functions that fail to be declared in header files.
-Wredundant-decls
Warn if anything is declared more than once in the same scope,
even in cases where multiple declaration is valid and changes
nothing.
-Wnested-externs
Warn if an extern declaration is encountered within an function.
-Wenum-clash
Warn about conversion between different enumeration types (C++
only).
-Woverloaded-virtual
(C++ only.) In a derived class, the definitions of virtual
functions must match the type signature of a virtual function
declared in the base class. Use this option to request warnings
when a derived class declares a function that may be an
erroneous attempt to define a virtual function: that is, warn
when a function with the same name as a virtual function in the
base class, but with a type signature that doesn't match any
virtual functions from the base class.
-Winline
Warn if a function can not be inlined, and either it was
declared as inline, or else the -finline-functions option was
given.
-Wprecomp
Warn if a precompiled header cannot be used.
-Wno-precomp
Suppress warnings when a precompiled header cannot be used.
-Werror
Treat warnings as errors; abort compilation after any warning.
DEBUGGING OPTIONScc has various special options that are used for debugging either your
program or cc:
-g Produce debugging information in the operating system's native
format. GDB can work with this debugging information.
On most systems that use stabs format, `-g' enables use of extra
debugging information that only GDB can use; this extra
information makes debugging work better in GDB but will probably
make other debuggers crash or refuse to read the program.
Unlike most other C compilers, cc allows you to use `-g' with
`-O'. The shortcuts taken by optimized code may occasionally
produce surprising results: some variables you declared may not
exist at all; flow of control may briefly move where you did not
expect it; some statements may not be executed because they
compute constant results or their values were already at hand;
some statements may execute in different places because they
were moved out of loops.
Nevertheless it proves possible to debug optimized output. This
makes it reasonable to use the optimizer for programs that might
have bugs.
The following options are useful when cc is generated with the
capability for more than one debugging format.
-ggdb Produce debugging information in the native format (if that is
supported), including GDB extensions if at all possible.
-p Generate extra code to write profile information suitable for
the analysis program prof.
-pg Generate extra code to write profile information suitable for
the analysis program gprof.
-a Generate extra code to write profile information for basic
blocks, which will record the number of times each basic block
is executed. This data could be analyzed by a program like
tcov. Note, however, that the format of the data is not what
tcov expects. Eventually GNU gprof should be extended to
process this data.
-dletters
Says to make debugging dumps during compilation at times
specified by letters. This is used for debugging the compiler.
The file names for most of the dumps are made by appending a
word to the source file name (e.g. `foo.c.rtl' or
`foo.c.jump').
-dM Dump all macro definitions, at the end of preprocessing, and
write no output.
-dN Dump all macro names, at the end of preprocessing.
-dD Dump all macro definitions, at the end of preprocessing, in
addition to normal output.
-dy Dump debugging information during parsing, to standard error.
-dr Dump after RTL generation, to `file.rtl'.
-dx Just generate RTL for a function instead of compiling it.
Usually used with `r'.
-dj Dump after first jump optimization, to `file.jump'.
-ds Dump after CSE (including the jump optimization that sometimes
follows CSE), to `file.cse'.
-dL Dump after loop optimization, to `file.loop'.
-dt Dump after the second CSE pass (including the jump optimization
that sometimes follows CSE), to `file.cse2'.
-df Dump after flow analysis, to `file.flow'.
-dc Dump after instruction combination, to `file.combine'.
-dS Dump after the first instruction scheduling pass, to
`file.sched'.
-dl Dump after local register allocation, to `file.lreg'.
-dg Dump after global register allocation, to `file.greg'.
-dR Dump after the second instruction scheduling pass, to
`file.sched2'.
-dJ Dump after last jump optimization, to `file.jump2'.
-dd Dump after delayed branch scheduling, to `file.dbr'.
-dk Dump after conversion from registers to stack, to `file.stack'.
-da Produce all the dumps listed above.
-dm Print statistics on memory usage, at the end of the run, to
standard error.
-dp Annotate the assembler output with a comment indicating which
pattern and alternative was used.
-fpretend-float
When running a cross-compiler, pretend that the target machine
uses the same floating point format as the host machine. This
causes incorrect output of the actual floating constants, but
the actual instruction sequence will probably be the same as cc
would make when running on the target machine.
-save-temps
Store the usual “temporary” intermediate files permanently;
place them in the current directory and name them based on the
source file. Thus, compiling `foo.c' with `-c -save-temps'
would produce files `foo.cpp' and `foo.s', as well as `foo.o'.
-print-libgcc-file-name
Print the full absolute name of the library file `libgcc.a' that
would be used when linking—and do not do anything else. With
this option, cc does not compile or link anything; it just
prints the file name.
OPTIMIZATION OPTIONS
These options control various sorts of optimizations:
-O
-O1 Optimize. Optimizing compilation takes somewhat more time, and
a lot more memory for a large function.
Without `-O', the compiler's goal is to reduce the cost of
compilation and to make debugging produce the expected results.
Statements are independent: if you stop the program with a
breakpoint between statements, you can then assign a new value
to any variable or change the program counter to any other
statement in the function and get exactly the results you would
expect from the source code.
Without `-O', only variables declared register are allocated in
registers. The resulting compiled code is a little worse than
produced by PCC without `-O'.
With `-O', the compiler tries to reduce code size and execution
time.
When you specify `-O', `-fthread-jumps' and `-fdelayed-branch'
are turned on. On some machines other flags may also be turned
on.
-O2 Optimize even more. Nearly all supported optimizations that do
not involve a space-speed tradeoff are performed. As compared
to -O, this option increases both compilation time and the
performance of the generated code.
-O2 turns on all -fflag options that enable more optimization,
except for -funroll-loops, -funroll-all-loops and
-fomit-frame-pointer.
-O0 Do not optimize.
If you use multiple -O options, with or without level numbers,
the last such option is the one that is effective.
Options of the form `-fflag' specify machine-independent flags. Most
flags have both positive and negative forms; the negative form of
`-ffoo' would be `-fno-foo'. The following list shows only one form—
the one which is not the default. You can figure out the other form by
either removing `no-' or adding it.
-ffloat-store
Do not store floating point variables in registers. This
prevents undesirable excess precision on machines such as the
68000 where the floating registers (of the 68881) keep more
precision than a double is supposed to have.
For most programs, the excess precision does only good, but a
few programs rely on the precise definition of IEEE floating
point. Use `-ffloat-store' for such programs.
-fmemoize-lookups
-fsave-memoized
Use heuristics to compile faster (C++ only). These heuristics
are not enabled by default, since they are only effective for
certain input files. Other input files compile more slowly.
The first time the compiler must build a call to a member
function (or reference to a data member), it must (1) determine
whether the class implements member functions of that name; (2)
resolve which member function to call (which involves figuring
out what sorts of type conversions need to be made); and (3)
check the visibility of the member function to the caller. All
of this adds up to slower compilation. Normally, the second
time a call is made to that member function (or reference to
that data member), it must go through the same lengthy process
again. This means that code like this
cout << "This " << p << " has " << n << " legs.\n";
makes six passes through all three steps. By using a software
cache, a “hit” significantly reduces this cost. Unfortunately,
using the cache introduces another layer of mechanisms which
must be implemented, and so incurs its own overhead.
`-fmemoize-lookups' enables the software cache.
Because access privileges (visibility) to members and member
functions may differ from one function context to the next, cc
may need to flush the cache. With the `-fmemoize-lookups' flag,
the cache is flushed after every function that is compiled. The
`-fsave-memoized' flag enables the same software cache, but when
the compiler determines that the context of the last function
compiled would yield the same access privileges of the next
function to compile, it preserves the cache. This is most
helpful when defining many member functions for the same class:
with the exception of member functions which are friends of
other classes, each member function has exactly the same access
privileges as every other, and the cache need not be flushed.
-fno-default-inline
Don't make member functions inline by default merely because
they are defined inside the class scope (C++ only).
-fno-defer-pop
Always pop the arguments to each function call as soon as that
function returns. For machines which must pop arguments after a
function call, the compiler normally lets arguments accumulate
on the stack for several function calls and pops them all at
once.
-fforce-mem
Force memory operands to be copied into registers before doing
arithmetic on them. This may produce better code by making all
memory references potential common subexpressions. When they
are not common subexpressions, instruction combination should
eliminate the separate register-load. I am interested in
hearing about the difference this makes.
-fforce-addr
Force memory address constants to be copied into registers
before doing arithmetic on them. This may produce better code
just as `-fforce-mem' may. I am interested in hearing about the
difference this makes.
-fomit-frame-pointer
Don't keep the frame pointer in a register for functions that
don't need one. This avoids the instructions to save, set up
and restore frame pointers; it also makes an extra register
available in many functions. It also makes debugging impossible
on most machines.
On some machines, such as the Vax, this flag has no effect,
because the standard calling sequence automatically handles the
frame pointer and nothing is saved by pretending it doesn't
exist. The machine-description macro FRAME_POINTER_REQUIRED
controls whether a target machine supports this flag.
-finline-functions
Integrate all simple functions into their callers. The compiler
heuristically decides which functions are simple enough to be
worth integrating in this way.
If all calls to a given function are integrated, and the
function is declared static, then cc normally does not output
the function as assembler code in its own right.
-fcaller-saves
Enable values to be allocated in registers that will be
clobbered by function calls, by emitting extra instructions to
save and restore the registers around such calls. Such
allocation is done only when it seems to result in better code
than would otherwise be produced.
This option is enabled by default on certain machines, usually
those which have no call-preserved registers to use instead.
-fkeep-inline-functions
Even if all calls to a given function are integrated, and the
function is declared static, nevertheless output a separate run-
time callable version of the function.
-fno-function-cse
Do not put function addresses in registers; make each
instruction that calls a constant function contain the
function's address explicitly.
This option results in less efficient code, but some strange
hacks that alter the assembler output may be confused by the
optimizations performed when this option is not used.
-fno-peephole
Disable any machine-specific peephole optimizations.
-ffast-math
This option allows cc to violate some ANSI or IEEE
rules/specifications in the interest of optimizing code for
speed. For example, it allows the compiler to assume arguments
to the sqrt function are non-negative numbers.
This option should never be turned on by any `-O' option since
it can result in incorrect output for programs which depend on
an exact implementation of IEEE or ANSI rules/specifications for
math functions.
The following options control specific optimizations. The `-O2' option
turns on all of these optimizations except `-funroll-loops' and
`-funroll-all-loops'.
The `-O' option usually turns on the `-fthread-jumps' and
`-fdelayed-branch' options, but specific machines may change the
default optimizations.
You can use the following flags in the rare cases when “fine-tuning” of
optimizations to be performed is desired.
-fstrength-reduce
Perform the optimizations of loop strength reduction and
elimination of iteration variables.
-fthread-jumps
Perform optimizations where we check to see if a jump branches
to a location where another comparison subsumed by the first is
found. If so, the first branch is redirected to either the
destination of the second branch or a point immediately
following it, depending on whether the condition is known to be
true or false.
-funroll-loops
Perform the optimization of loop unrolling. This is only done
for loops whose number of iterations can be determined at
compile time or run time.
-funroll-all-loops
Perform the optimization of loop unrolling. This is done for
all loops. This usually makes programs run more slowly.
-fcse-follow-jumps
In common subexpression elimination, scan through jump
instructions when the target of the jump is not reached by any
other path. For example, when CSE encounters an if statement
with an else clause, CSE will follow the jump when the condition
tested is false.
-fcse-skip-blocks
This is similar to `-fcse-follow-jumps', but causes CSE to
follow jumps which conditionally skip over blocks. When CSE
encounters a simple if statement with no else clause,
`-fcse-skip-blocks' causes CSE to follow the jump around the
body of the if.
-frerun-cse-after-loop
Re-run common subexpression elimination after loop optimizations
has been performed.
-felide-constructors
Elide constructors when this seems plausible (C++ only). With
this flag, cc initializes y directly from the call to foo
without going through a temporary in the following code:
A foo (); A y = foo ();
Without this option, cc first initializes y by calling the
appropriate constructor for type A; then assigns the result of
foo to a temporary; and, finally, replaces the initial valyue of
`y' with the temporary.
The default behavior (`-fno-elide-constructors') is specified by
the draft ANSI C++ standard. If your program's constructors
have side effects, using `-felide-constructors' can make your
program act differently, since some constructor calls may be
omitted.
-fexpensive-optimizations
Perform a number of minor optimizations that are relatively
expensive.
-fdelayed-branch
If supported for the target machine, attempt to reorder
instructions to exploit instruction slots available after
delayed branch instructions.
-fschedule-insns
If supported for the target machine, attempt to reorder
instructions to eliminate execution stalls due to required data
being unavailable. This helps machines that have slow floating
point or memory load instructions by allowing other instructions
to be issued until the result of the load or floating point
instruction is required.
-fschedule-insns2
Similar to `-fschedule-insns', but requests an additional pass
of instruction scheduling after register allocation has been
done. This is especially useful on machines with a relatively
small number of registers and where memory load instructions
take more than one cycle.
MACHINE DEPENDENT OPTIONS
Each of the target machine types can have its own special options,
starting with `-m', to choose among various hardware models or
configurations—for example, 68010 vs 68020, floating coprocessor or
none. A single installed version of the compiler can compile for any
model or configuration, according to the options specified.
Some configurations of the compiler also support additional special
options, usually for command-line compatibility with other compilers on
the same platform.
These are the `-m' options defined for the 68000 series:
-m68000
-mc68000
Generate output for a 68000. This is the default when the
compiler is configured for 68000-based systems.
-m68020
-mc68020
Generate output for a 68020 (rather than a 68000). This is the
default when the compiler is configured for 68020-based systems.
-m68881
Generate output containing 68881 instructions for floating
point. This is the default for most 68020-based systems unless
-nfp was specified when the compiler was configured.
-m68030
Generate output for a 68030. This is the default when the
compiler is configured for 68030-based systems.
-m68040
Generate output for a 68040. This is the default when the
compiler is configured for 68040-based systems.
-m68020-40
Generate output for a 68040, without using any of the new
instructions. This results in code which can run relatively
efficiently on either a 68020/68881 or a 68030 or a 68040.
-mfpa Generate output containing Sun FPA instructions for floating
point.
-msoft-float
Generate output containing library calls for floating point.
WARNING: the requisite libraries are not part of the GNU C
compiler. Normally the facilities of the machine's usual C
compiler are used, but this can't be done directly in cross-
compilation. You must make your own arrangements to provide
suitable library functions for cross-compilation.
-mshort
Consider type int to be 16 bits wide, like short int.
-mnobitfield
Do not use the bit-field instructions. `-m68000' implies
`-mnobitfield'.
-mbitfield
Do use the bit-field instructions. `-m68020' implies
`-mbitfield'. This is the default if you use the unmodified
sources.
-mrtd Use a different function-calling convention, in which functions
that take a fixed number of arguments return with the rtd
instruction, which pops their arguments while returning. This
saves one instruction in the caller since there is no need to
pop the arguments there.
This calling convention is incompatible with the one normally
used on Unix, so you cannot use it if you need to call libraries
compiled with the Unix compiler.
Also, you must provide function prototypes for all functions
that take variable numbers of arguments (including printf);
otherwise incorrect code will be generated for calls to those
functions.
In addition, seriously incorrect code will result if you call a
function with too many arguments. (Normally, extra arguments
are harmlessly ignored.)
The rtd instruction is supported by the 68010 and 68020
processors, but not by the 68000.
These `-m' options are defined for the Intel 80386 family of computers:
-m486
-mno-486
Control whether or not code is optimized for a 486 instead of an
386. Code generated for a 486 will run on a 386 and vice versa.
-msoft-float
Generate output containing library calls for floating point.
Warning: the requisite libraries are not part of the GNU C
compiler. Normally the facilities of the machine's usual C
compiler are used, but this can't be done directly in cross-
compilation. You must make your own arrangements to provide
suitable library functions for cross-compilation.
On machines where a function returns floating point results in
the 80387 register stack, some floating point opcodes may be
emitted even if `-msoft-float' is used.
-mno-fp-ret-in-387
Do not use the FPU registers for return values of functions.
The usual calling convention has functions return values of
types float and double in an FPU register, even if there is no
FPU. The idea is that the operating system should emulate an
FPU.
The option `-mno-fp-ret-in-387' causes such values to be
returned in ordinary CPU registers instead.
These `-m' options are defined for the HPPA family of computers:
-mpa-risc-1-0
Generate code for a PA 1.0 processor.
-mpa-risc-1-1
Generate code for a PA 1.1 processor.
-mkernel
Generate code which is suitable for use in kernels.
Specifically, avoid add instructions in which one of the
arguments is the DP register; generate addil instructions
instead. This avoids a rather serious bug in the HP-UX linker.
-mshared-libs
Generate code that can be linked against HP-UX shared libraries.
This option is not fully function yet, and is not on by default
for any PA target. Using this option can cause incorrect code
to be generated by the compiler.
-mno-shared-libs
Don't generate code that will be linked against shared
libraries. This is the default for all PA targets.
-mlong-calls
Generate code which allows calls to functions greater than 256K
away from the caller when the caller and callee are in the same
source file. Do not turn this option on unless code refuses to
link with “branch out of range errors from the linker.
-mdisable-fpregs
Prevent floating point registers from being used in any manner.
This is necessary for compiling kernels which perform lazy
context switching of floating point registers. If you use this
option and attempt to perform floating point operations, the
compiler will abort.
-mdisable-indexing
Prevent the compiler from using indexing address modes. This
avoids some rather obscure problems when compiling MIG generated
code under MACH.
-mtrailing-colon
Add a colon to the end of label definitions (for ELF
assemblers).
CODE GENERATION OPTIONS
These machine-independent options control the interface conventions
used in code generation.
Most of them begin with `-f'. These options have both positive and
negative forms; the negative form of `-ffoo' would be `-fno-foo'. In
the table below, only one of the forms is listed—the one which is not
the default. You can figure out the other form by either removing
`no-' or adding it.
-fnonnull-objects
Assume that objects reached through references are not null (C++
only).
Normally, cc makes conservative assumptions about objects
reached through references. For example, the compiler must
check that a is not null in code like the following:
obj &a = g (); a.f (2);
Checking that references of this sort have non-null values
requires extra code, however, and it is unnecessary for many
programs. You can use `-fnonnull-objects' to omit the checks
for null, if your program doesn't require checking.
-fpcc-struct-return
Use the same convention for returning struct and union values
that is used by the usual C compiler on your system. This
convention is less efficient for small structures, and on many
machines it fails to be reentrant; but it has the advantage of
allowing intercallability between GCC-compiled code and PCC-
compiled code.
-freg-struct-return
Use the convention that struct and union values are returned in
registers when possible. This is more efficient for small
structures than -fpcc-struct-return.
If you specify neither -fpcc-struct-return nor
-freg-struct-return, cc defaults to whichever convention is
standard for the target. If there is no standard convention, cc
defaults to -fpcc-struct-return.
-fshort-enums
Allocate to an enum type only as many bytes as it needs for the
declared range of possible values. Specifically, the enum type
will be equivalent to the smallest integer type which has enough
room.
-fshort-double
Use the same size for double as for float .
-fshared-data
Requests that the data and non-const variables of this
compilation be shared data rather than private data. The
distinction makes sense only on certain operating systems, where
shared data is shared between processes running the same
program, while private data exists in one copy per process.
-fno-common
Allocate even uninitialized global variables in the bss section
of the object file, rather than generating them as common
blocks. This has the effect that if the same variable is
declared (without extern) in two different compilations, you
will get an error when you link them. The only reason this
might be useful is if you wish to verify that the program will
work on other systems which always work this way.
-fno-gnu-linker
Do not output global initializations (such as C++ constructors
and destructors) in the form used by the GNU linker (on systems
where the GNU linker is the standard method of handling them).
Use this option when you want to use a non-GNU linker, which
also requires using the collect2 program to make sure the system
linker includes constructors and destructors. (collect2 is
included in the GNU C distribution.) For systems which must use
collect2, the compiler driver gcc is configured to do this
automatically.
-finhibit-size-directive
Don't output a .size assembler directive, or anything else that
would cause trouble if the function is split in the middle, and
the two halves are placed at locations far apart in memory.
This option is used when compiling `crtstuff.c'; you should not
need to use it for anything else.
-fverbose-asm
Put extra commentary information in the generated assembly code
to make it more readable. This option is generally only of use
to those who actually need to read the generated assembly code
(perhaps while debugging the compiler itself).
-fvolatile
Consider all memory references through pointers to be volatile.
-fvolatile-global
Consider all memory references to extern and global data items
to be volatile.
-ffixed-reg
Treat the register named reg as a fixed register; generated code
should never refer to it (except perhaps as a stack pointer,
frame pointer or in some other fixed role).
reg must be the name of a register. The register names accepted
are machine-specific and are defined in the REGISTER_NAMES macro
in the machine description macro file.
This flag does not have a negative form, because it specifies a
three-way choice.
-fcall-used-reg
Treat the register named reg as an allocatable register that is
clobbered by function calls. It may be allocated for
temporaries or variables that do not live across a call.
Functions compiled this way will not save and restore the
register reg.
Use of this flag for a register that has a fixed pervasive role
in the machine's execution model, such as the stack pointer or
frame pointer, will produce disastrous results.
This flag does not have a negative form, because it specifies a
three-way choice.
-fcall-saved-reg
Treat the register named reg as an allocatable register saved by
functions. It may be allocated even for temporaries or
variables that live across a call. Functions compiled this way
will save and restore the register reg if they use it.
Use of this flag for a register that has a fixed pervasive role
in the machine's execution model, such as the stack pointer or
frame pointer, will produce disastrous results.
A different sort of disaster will result from the use of this
flag for a register in which function values may be returned.
This flag does not have a negative form, because it specifies a
three-way choice.
Two `
#pragma' directives are supported for cc, to permit using the same
header file for two purposes: as a definition of interfaces to a given
object class, and as the full definition of the contents of that object
class.
#pragma interface
(C++ only.) Use this directive in header files that define
object classes, to save space in most of the object files that
use those classes. Normally, local copies of certain
information (backup copies of inline member functions, debugging
information, and the internal tables that implement virtual
functions) must be kept in each object file that includes class
definitions. You can use this pragma to avoid such duplication.
When a header file containing `#pragma interface' is included in
a compilation, this auxiliary information will not be generated
(unless the main input source file itself uses `#pragma
implementation'). Instead, the object files will contain
references to be resolved at link time.
#pragma implementation
#pragma implementation "objects.h"
(C++ only.) Use this pragma in a main input file, when you want
full output from included header files to be generated (and made
globally visible). The included header file, in turn, should
use `#pragma interface'. Backup copies of inline member
functions, debugging information, and the internal tables used
to implement virtual functions are all generated in
implementation files.
If you use `#pragma implementation' with no argument, it applies
to an include file with the same basename as your source file;
for example, in `allclass.cc', `#pragma implementation' by
itself is equivalent to `#pragma implementation "allclass.h"'.
Use the string argument if you want a single implementation file
to include code from multiple header files.
There is no way to split up the contents of a single header file
into multiple implementation files.
FILES
file.c C source file
file.h C header (preprocessor) file
file.i preprocessed C source file
file.C C++ source file
file.cc C++ source file
file.cxx C++ source file
file.m Objective-C source file
file.M Objective-C++ source file
file.s assembly language file
file.o object file
a.out link edited output
tmp/cc∗ temporary files
lib/archcpp preprocessor
lib/archcc1 compiler for C
lib/archcc1objplus
compiler for C++
lib/archcollect linker front end needed on some machines
libcrt[01n].o start-up routine
lib/archccrt0 additional start-up routine for C++
liblibc.a standard C library, see intro(3)
usrinclude standard directory for #include files
lib/archinclude standard cc directory for #include files
lib/archg++include
additional cc directory for #include files
SEE ALSOgdb(1), ld(1)Free Software Foundation, Inc. June 15, 1989 CC(1)
