lfcompile(5) Standards, Environments, and Macros lfcompile(5)NAMElfcompile - large file compilation environment for 32-bit applications
DESCRIPTION
All 64-bit applications can manipulate large files by default. The
methods described on this page allow 32-bit applications to manipulate
large files.
In the large file compilation environment, source interfaces are bound
to appropriate 64-bit functions, structures, and types. Compiling in
this environment allows 32-bit applications to access files whose size
is greater than or equal to 2 Gbyte ( 2^31 bytes).
Each interface named xxx() that needs to access 64-bit entities to
access large files maps to a xxx64() call in the resulting binary. All
relevant data types are defined to be of correct size (for example,
off_t has a typedef definition for a 64-bit entity).
An application compiled in this environment is able to use the xxx()
source interfaces to access both large and small files, rather than
having to explicitly utilize the transitional xxx64() interface calls
to access large files. See the lfcompile64(5) manual page for informa‐
tion regarding the transitional compilation environment.
Applications can be compiled in the large file compilation environment
by using the following methods:
o Use the getconf(1) utility with one or more of the arguments
listed in the table below. This method is recommended for
portable applications.
┌──────────────────┬────────────────────────────────────────┐
│ argument │ purpose │
├──────────────────┼────────────────────────────────────────┤
│LFS_CFLAGS │ obtain compilation flags necessary to │
│ │ enable the large file compilation │
│ │ environment │
│LFS_LDFLAGS │ obtain link editor options │
│LFS_LIBS │ obtain link library names │
│LFS_LINTFLAGS │ obtain lint options │
└──────────────────┴────────────────────────────────────────┘
o Set the compile-time flag _FILE_OFFSET_BITS to 64 before
including any headers. Applications may combine objects pro‐
duced in the large file compilation environment with objects
produced in the transitional compilation environment, but
must be careful with respect to interoperability between
those objects. Applications should not declare global vari‐
ables of types whose sizes change between compilation envi‐
ronments.
Access to Additional Large File Interfaces
The fseek() and ftell() functions do not map to functions named
fseek64() and ftell64(); rather, the large file additions fseeko() and
ftello(), have functionality identical to fseek() and ftell() and do
map to the 64-bit functions fseeko64() and ftello64(). Applications
wishing to access large files should use fseeko() and ftello() in place
of fseek() and ftell(). See the fseek(3C) and ftell(3C) manual pages
for information about fseeko() and ftello().
Applications wishing to access fseeko() and ftello() as well as the
POSIX and X/Open specification-conforming interfaces should define the
macro _LARGEFILE_SOURCE to be 1 and set whichever feature test macros
are appropriate to obtain the desired environment (see standards(5)).
EXAMPLES
In the following examples, the large file compilation environment is
accessed by invoking the getconf utility with one of the arguments
listed in the table above. The additional large file interfaces are
accessed by specifying -D_LARGEFILE_SOURCE.
The examples that use the form of command substitution specifying the
command within parentheses preceded by a dollar sign can be executed
only in a POSIX-conforming shell such as the Korn Shell (see ksh(1)).
In a shell that is not POSIX-conforming, such as the Bourne Shell (see
sh(1)) and the C Shell (see csh(1)), the getconf calls must be enclosed
within grave accent marks, as shown in the second example.
Example 1 Compile a program with a "large" off_t that uses fseeko(),
ftello(), and yacc.
The following example compiles a program with a "large" off_t and uses
fseeko(), ftello(), and yacc(1).
$ c89 -D_LARGEFILE_SOURCE \
-D_FILE_OFFSET_BITS=64 -o foo \
$(getconf LFS_CFLAGS) y.tab.c b.o \
$(getconf LFS_LDFLAGS) \
-ly $(getconf LFS_LIBS)
Example 2 Compile a program with a "large" off_t that does not use
fseeko() and ftello() and has no application specific libraries.
% c89 -D_FILE_OFFSET_BITS=64 \
`getconf LFS_CFLAGS` a.c \
`getconf LFS_LDFLAGS` \
`getconf LFS_LIBS` \
Example 3 Compile a program with a "default" off_t that uses fseeko()
and ftello().
$ c89 -D_LARGEFILE_SOURCE a.c
SEE ALSOcsh(1), getconf(1), ksh(1), yacc(1), lint(1B), sh(1), fseek(3C),
ftell(3C), lf64(5), lfcompile64(5), standards(5)NOTES
Certain system-specific or non-portable interfaces are not usable in
the large file compilation environment. Known cases are:
o Kernel data structures read from /dev/kmem.
o Interfaces in the kernel virtual memory library, -lkvm.
o Interfaces in the ELF access library, -lelf.
o Interfaces to /proc defined in <procfs.h>.
o The ustat(2) system call.
Programs that use these interfaces should not be compiled in the large
file compilation environment. As a partial safeguard against making
this mistake, including either of the <libelf.h> or <sys/procfs.h>
header files will induce a compilation error when the large file compi‐
lation environment is enabled.
In general, caution should be exercised when using any separately-com‐
piled library whose interfaces include data items of type off_t or the
other redefined types either directly or indirectly, such as with
'struct stat'. (The redefined types are off_t, rlim_t, ino_t, blkcnt_t,
fsblkcnt_t, and fsfilcnt_t.) For the large file compilation environment
to work correctly with such a library, the library interfaces must
include the appropriate xxx64() binary entry points and must have them
mapped to the corresponding primary functions when _FILE_OFFSET_BITS is
set to 64.
Care should be exercised using any of the printf() or scanf() routines
on variables of the types mentioned above. In the large file compila‐
tion environment, these variables should be printed or scanned using
long long formats.
BUGS
The lint(1B) utility will generate spurious error messages when
_FILE_OFFSET_BITS is set to 64. This is because the binary libc lint
library, /usr/lib/llib-lc.ln, is compiled only for the standard inter‐
faces, not with _FILE_OFFSET_BITS set to 64. This deficiency hampers
static error-checking for programs compiled in the large file compila‐
tion environment.
Symbolic formats analogous to those found in <sys/int_fmtio.h> do not
exist for printing or scanning variables of the types that are rede‐
fined in the large file compilation environment.
SunOS 5.10 23 Jul 2001 lfcompile(5)
