ANTLR(1) PCCTS Manual Pages ANTLR(1)NAMEantlr - ANother Tool for Language Recognition
SYNTAXantlr [options] grammar_files
Antlr converts an extended form of context-free grammar into a set of C
functions which directly implement an efficient form of deterministic
recursive-descent LL(k) parser. Context-free grammars may be augmented
with predicates to allow semantics to influence parsing; this allows a
form of context-sensitive parsing. Selective backtracking is also
available to handle non-LL(k) and even non-LALR(k) constructs. Antlr
also produces a definition of a lexer which can be automatically con‐
verted into C code for a DFA-based lexer by dlg. Hence, antlr serves a
function much like that of yacc, however, it is notably more flexible
and is more integrated with a lexer generator (antlr directly generates
dlg code, whereas yacc and lex are given independent descriptions).
Unlike yacc which accepts LALR(1) grammars, antlr accepts LL(k) gram‐
mars in an extended BNF notation — which eliminates the need for prece‐
Like yacc grammars, antlr grammars can use automatically-maintained
symbol attribute values referenced as dollar variables. Further,
because antlr generates top-down parsers, arbitrary values may be
inherited from parent rules (passed like function parameters). Antlr
also has a mechanism for creating and manipulating abstract-syntax-
There are various other niceties in antlr, including the ability to
spread one grammar over multiple files or even multiple grammars in a
single file, the ability to generate a version of the grammar with
actions stripped out (for documentation purposes), and lots more.
OPTIONS-ck n Use up to n symbols of lookahead when using compressed (linear
approximation) lookahead. This type of lookahead is very cheap
to compute and is attempted before full LL(k) lookahead, which
is of exponential complexity in the worst case. In general, the
compressed lookahead can be much deeper (e.g, -ck 10) than the
full lookahead (which usually must be less than 4).
-CC Generate C++ output from both ANTLR and DLG.
-cr Generate a cross-reference for all rules. For each rule, print
a list of all other rules that reference it.
-e1 Ambiguities/errors shown in low detail (default).
-e2 Ambiguities/errors shown in more detail.
-e3 Ambiguities/errors shown in excruciating detail.
Rename err.c to file.
Rename stdpccts.h header (turns on -gh) to file.
Rename lexical output, parser.dlg, to file.
Rename file with lexical mode definitions, mode.h, to file.
Rename file which remaps globally visible symbols, remap.h, to
Rename tokens.h to file.
-ga Generate ANSI-compatible code (default case). This has not been
rigorously tested to be ANSI XJ11 C compliant, but it is close.
The normal output of antlr is currently compilable under both
K&R, ANSI C, and C++—this option does nothing because antlr gen‐
erates a bunch of #ifdef's to do the right thing depending on
-gc Indicates that antlr should generate no C code, i.e., only per‐
form analysis on the grammar.
-gd C code is inserted in each of the antlr generated parsing func‐
tions to provide for user-defined handling of a detailed parse
trace. The inserted code consists of calls to the user-supplied
macros or functions called zzTRACEIN and zzTRACEOUT. The only
argument is a char * pointing to a C-style string which is the
grammar rule recognized by the current parsing function. If no
definition is given for the trace functions, upon rule entry and
exit, a message will be printed indicating that a particular
rule as been entered or exited.
-ge Generate an error class for each non-terminal.
-gh Generate stdpccts.h for non-ANTLR-generated files to include.
This file contains all defines needed to describe the type of
parser generated by antlr (e.g. how much lookahead is used and
whether or not trees are constructed) and contains the header
action specified by the user.
-gk Generate parsers that delay lookahead fetches until needed.
Without this option, antlr generates parsers which always have k
tokens of lookahead available.
-gl Generate line info about grammar actions in C parser of the form
# line "file" which makes error messages from the C/C++ compiler
make more sense as they will point into the grammar file not the
resulting C file. Debugging is easier as well, because you will
step through the grammar not C file.
-gs Do not generate sets for token expression lists; instead gener‐
ate a ||-separated sequence of LA(1)==token_number. The default
is to generate sets.
-gt Generate code for Abstract-Syntax Trees.
-gx Do not create the lexical analyzer files (dlg-related). This
option should be given when the user wishes to provide a custom‐
ized lexical analyzer. It may also be used in make scripts to
cause only the parser to be rebuilt when a change not affecting
the lexical structure is made to the input grammars.
-k n Set k of LL(k) to n; i.e. set tokens of look-ahead (default==1).
-o dir Directory where output files should go (default="."). This is
very nice for keeping the source directory clear of ANTLR and
-p The complete grammar, collected from all input grammar files and
stripped of all comments and embedded actions, is listed to std‐
out. This is intended to aid in viewing the entire grammar as a
whole and to eliminate the need to keep actions concisely stated
so that the grammar is easier to read. Hence, it is preferable
to embed even complex actions directly in the grammar, rather
than to call them as subroutines, since the subroutine call
overhead will be saved.
-pa This option is the same as -p except that the output is anno‐
tated with the first sets determined from grammar analysis.
Turn on the computation and hoisting of predicate context.
Turn off the computation and hoisting of predicate context.
This option makes 1.10 behave like the 1.06 release with option
-pr on. Context computation is off by default.
-rl n Limit the maximum number of tree nodes used by grammar analysis
to n. Occasionally, antlr is unable to analyze a grammar sub‐
mitted by the user. This rare situation can only occur when the
grammar is large and the amount of lookahead is greater than
one. A nonlinear analysis algorithm is used by PCCTS to handle
the general case of LL(k) parsing. The average complexity of
analysis, however, is near linear due to some fancy footwork in
the implementation which reduces the number of calls to the full
LL(k) algorithm. An error message will be displayed, if this
limit is reached, which indicates the grammar construct being
analyzed when antlr hit a non-linearity. Use this option if
antlr seems to go out to lunch and your disk start thrashing;
try n=10000 to start. Once the offending construct has been
identified, try to remove the ambiguity that antlr was trying to
overcome with large lookahead analysis. The introduction of
(...)? backtracking blocks eliminates some of these problems —
antlr does not analyze alternatives that begin with (...)? (it
simply backtracks, if necessary, at run time).
-w1 Set low warning level. Do not warn if semantic predicates
and/or (...)? blocks are assumed to cover ambiguous alterna‐
-w2 Ambiguous parsing decisions yield warnings even if semantic
predicates or (...)? blocks are used. Warn if predicate context
computed and semantic predicates incompletely disambiguate
- Read grammar from standard input and generate stdin.c as the
Antlr works... we think. There is no implicit guarantee of anything.
We reserve no legal rights to the software known as the Purdue Compiler
Construction Tool Set (PCCTS) — PCCTS is in the public domain. An
individual or company may do whatever they wish with source code dis‐
tributed with PCCTS or the code generated by PCCTS, including the
incorporation of PCCTS, or its output, into commercial software. We
encourage users to develop software with PCCTS. However, we do ask
that credit is given to us for developing PCCTS. By "credit", we mean
that if you incorporate our source code into one of your programs (com‐
mercial product, research project, or otherwise) that you acknowledge
this fact somewhere in the documentation, research report, etc... If
you like PCCTS and have developed a nice tool with the output, please
mention that you developed it using PCCTS. As long as these guidelines
are followed, we expect to continue enhancing this system and expect to
make other tools available as they are completed.
*.c output C parser.
*.cpp output C++ parser when C++ mode is used.
output dlg lexical analyzer.
err.c token string array, error sets and error support routines. Not
used in C++ mode.
file that redefines all globally visible parser symbols. The
use of the #parser directive creates this file. Not used in C++
list of definitions needed by C files, not generated by PCCTS,
that reference PCCTS objects. This is not generated by default.
Not used in C++ mode.
output #defines for tokens used and function prototypes for
functions generated for rules.
SEE ALSOdlg(1), pccts(1)ANTLR September 1995 ANTLR(1)