1OCAMLC(1) General Commands Manual OCAMLC(1)
2
6 ocamlc - The OCaml bytecode compiler
7
10 ocamlc [ options ] filename ...
11 ocamlc.opt [ options ] filename ...
13
16 The OCaml bytecode compiler ocamlc(1) compiles OCaml source files to
17 bytecode object files and links these object files to produce stand‐
18 alone bytecode executable files. These executable files are then run
19 by the bytecode interpreter ocamlrun(1).
20 The ocamlc(1) command has a command-line interface similar to the one
22 of most C compilers. It accepts several types of arguments and pro‐
23 cesses them sequentially, after all options have been processed:
24 Arguments ending in .mli are taken to be source files for compilation
26 unit interfaces. Interfaces specify the names exported by compilation
27 units: they declare value names with their types, define public data
28 types, declare abstract data types, and so on. From the file x.mli, the
29 ocamlc(1) compiler produces a compiled interface in the file x.cmi.
30 Arguments ending in .ml are taken to be source files for compilation
32 unit implementations. Implementations provide definitions for the names
33 exported by the unit, and also contain expressions to be evaluated for
34 their side-effects. From the file x.ml, the ocamlc(1) compiler pro‐
35 duces compiled object bytecode in the file x.cmo.
36 If the interface file x.mli exists, the implementation x.ml is checked
38 against the corresponding compiled interface x.cmi, which is assumed to
39 exist. If no interface x.mli is provided, the compilation of x.ml pro‐
40 duces a compiled interface file x.cmi in addition to the compiled ob‐
41 ject code file x.cmo. The file x.cmi produced corresponds to an inter‐
42 face that exports everything that is defined in the implementation
43 x.ml.
44 Arguments ending in .cmo are taken to be compiled object bytecode.
46 These files are linked together, along with the object files obtained
47 by compiling .ml arguments (if any), and the OCaml standard library, to
48 produce a standalone executable program. The order in which .cmo and.ml
49 arguments are presented on the command line is relevant: compilation
50 units are initialized in that order at run-time, and it is a link-time
51 error to use a component of a unit before having initialized it. Hence,
52 a given x.cmo file must come before all .cmo files that refer to the
53 unit x.
54 Arguments ending in .cma are taken to be libraries of object bytecode.
56 A library of object bytecode packs in a single file a set of object
57 bytecode files (.cmo files). Libraries are built with ocamlc -a (see
58 the description of the -a option below). The object files contained in
59 the library are linked as regular .cmo files (see above), in the order
60 specified when the .cma file was built. The only difference is that if
61 an object file contained in a library is not referenced anywhere in the
62 program, then it is not linked in.
63 Arguments ending in .c are passed to the C compiler, which generates a
65 .o object file. This object file is linked with the program if the
66 -custom flag is set (see the description of -custom below).
67 Arguments ending in .o or .a are assumed to be C object files and li‐
69 braries. They are passed to the C linker when linking in -custom mode
70 (see the description of -custom below).
71 Arguments ending in .so are assumed to be C shared libraries (DLLs).
73 During linking, they are searched for external C functions referenced
74 from the OCaml code, and their names are written in the generated byte‐
75 code executable. The run-time system ocamlrun(1) then loads them dy‐
76 namically at program start-up time.
77 The output of the linking phase is a file containing compiled bytecode
79 that can be executed by the OCaml bytecode interpreter: the command
80 ocamlrun(1). If caml.out is the name of the file produced by the link‐
81 ing phase, the command ocamlrun caml.out arg1 arg2 ... argn executes
82 the compiled code contained in caml.out, passing it as arguments the
83 character strings arg1 to argn. (See ocamlrun(1) for more details.)
84 On most systems, the file produced by the linking phase can be run di‐
86 rectly, as in: ./caml.out arg1 arg2 ... argn. The produced file has
87 the executable bit set, and it manages to launch the bytecode inter‐
88 preter by itself.
89 ocamlc.opt is the same compiler as ocamlc, but compiled with the na‐
91 tive-code compiler ocamlopt(1). Thus, it behaves exactly like ocamlc,
92 but compiles faster. ocamlc.opt may not be available in all installa‐
93 tions of OCaml.
94
97 The following command-line options are recognized by ocamlc(1).
98 -a Build a library (.cma file) with the object files (.cmo files)
100 given on the command line, instead of linking them into an exe‐
101 cutable file. The name of the library must be set with the -o
102 option.
103 If -custom, -cclib or -ccopt options are passed on the command
105 line, these options are stored in the resulting .cma library.
106 Then, linking with this library automatically adds back the
107 -custom, -cclib and -ccopt options as if they had been provided
108 on the command line, unless the -noautolink option is given. Ad‐
109 ditionally, a substring $CAMLORIGIN inside a -ccopt options
110 will be replaced by the full path to the .cma library, excluding
111 the filename. -absname Show absolute filenames in error mes‐
112 sages.
113 -annot Deprecated since 4.11. Please use -bin-annot instead.
115 -bin-annot
117 Dump detailed information about the compilation (types, bind‐
118 ings, tail-calls, etc) in binary format. The information for
119 file src.ml is put into file src.cmt. In case of a type error,
120 dump all the information inferred by the type-checker before the
121 error. The annotation files produced by -bin-annot contain more
122 information and are much more compact than the files produced by
123 -annot.
124 -c Compile only. Suppress the linking phase of the compilation.
126 Source code files are turned into compiled files, but no exe‐
127 cutable file is produced. This option is useful to compile mod‐
128 ules separately.
129 -cc ccomp
131 Use ccomp as the C linker when linking in "custom runtime" mode
132 (see the -custom option) and as the C compiler for compiling .c
133 source files.
134 -cclib -llibname
136 Pass the -llibname option to the C linker when linking in "cus‐
137 tom runtime" mode (see the -custom option). This causes the
138 given C library to be linked with the program.
139 -ccopt option
141 Pass the given option to the C compiler and linker, when linking
142 in "custom runtime" mode (see the -custom option). For instance,
143 -ccopt -Ldir causes the C linker to search for C libraries in
144 directory dir.
145 -color mode
147 Enable or disable colors in compiler messages (especially warn‐
148 ings and errors). The following modes are supported:
149 auto use heuristics to enable colors only if the output supports
151 them (an ANSI-compatible tty terminal);
152 always enable colors unconditionally;
154 never disable color output.
156 The default setting is auto, and the current heuristic checks
158 that the "TERM" environment variable exists and is not empty or
159 "dumb", and that isatty(stderr) holds.
160 The environment variable "OCAML_COLOR" is considered if -color
162 is not provided. Its values are auto/always/never as above.
163 -error-style mode
166 Control the way error messages and warnings are printed. The
167 following modes are supported:
168 short only print the error and its location;
170 contextual like "short", but also display the source code snip‐
172 pet corresponding to the location of the error.
173 The default setting is contextual.
175 The environment variable "OCAML_ERROR_STYLE" is considered if
177 -error-style is not provided. Its values are short/contextual as
178 above.
179 -compat-32
182 Check that the generated bytecode executable can run on 32-bit
183 platforms and signal an error if it cannot. This is useful when
184 compiling bytecode on a 64-bit machine.
185 -config
187 Print the version number of ocamlc(1) and a detailed summary of
188 its configuration, then exit.
189 -config-var
191 Print the value of a specific configuration variable from the
192 -config output, then exit. If the variable does not exist, the
193 exit code is non-zero.
194 -custom
196 Link in "custom runtime" mode. In the default linking mode, the
197 linker produces bytecode that is intended to be executed with
198 the shared runtime system, ocamlrun(1). In the custom runtime
199 mode, the linker produces an output file that contains both the
200 runtime system and the bytecode for the program. The resulting
201 file is larger, but it can be executed directly, even if the
202 ocamlrun(1) command is not installed. Moreover, the "custom run‐
203 time" mode enables linking OCaml code with user-defined C func‐
204 tions.
205 Never use the strip(1) command on executables produced by
207 ocamlc -custom, this would remove the bytecode part of the exe‐
208 cutable.
209 Security warning: never set the "setuid" or "setgid" bits on ex‐
211 ecutables produced by ocamlc -custom, this would make them vul‐
212 nerable to attacks.
213 -depend ocamldep-args
215 Compute dependencies, as ocamldep would do.
216 -dllib -llibname
218 Arrange for the C shared library dlllibname.so to be loaded dy‐
219 namically by the run-time system ocamlrun(1) at program start-up
220 time.
221 -dllpath dir
223 Adds the directory dir to the run-time search path for shared C
224 libraries. At link-time, shared libraries are searched in the
225 standard search path (the one corresponding to the -I option).
226 The -dllpath option simply stores dir in the produced executable
227 file, where ocamlrun(1) can find it and use it.
228 -for-pack module-path
230 Generate an object file (.cmo file) that can later be included
231 as a sub-module (with the given access path) of a compilation
232 unit constructed with -pack. For instance,
233 ocamlc -for-pack P -c A.ml will generate a.cmo that can later be
234 used with ocamlc -pack -o P.cmo a.cmo. Note: you can still pack
235 a module that was compiled without -for-pack but in this case
236 exceptions will be printed with the wrong names.
237 -g Add debugging information while compiling and linking. This op‐
239 tion is required in order to be able to debug the program with
240 ocamldebug(1) and to produce stack backtraces when the program
241 terminates on an uncaught exception.
242 -i Cause the compiler to print all defined names (with their in‐
244 ferred types or their definitions) when compiling an implementa‐
245 tion (.ml file). No compiled files (.cmo and .cmi files) are
246 produced. This can be useful to check the types inferred by the
247 compiler. Also, since the output follows the syntax of inter‐
248 faces, it can help in writing an explicit interface (.mli file)
249 for a file: just redirect the standard output of the compiler to
250 a .mli file, and edit that file to remove all declarations of
251 unexported names.
252 -I directory
254 Add the given directory to the list of directories searched for
255 compiled interface files (.cmi), compiled object code files
256 (.cmo), libraries (.cma), and C libraries specified with
257 -cclib -lxxx . By default, the current directory is searched
258 first, then the standard library directory. Directories added
259 with -I are searched after the current directory, in the order
260 in which they were given on the command line, but before the
261 standard library directory. See also option -nostdlib.
262 If the given directory starts with +, it is taken relative to
264 the standard library directory. For instance, -I +compiler-libs
265 adds the subdirectory compiler-libs of the standard library to
266 the search path.
267 -impl filename
269 Compile the file filename as an implementation file, even if its
270 extension is not .ml.
271 -intf filename
273 Compile the file filename as an interface file, even if its ex‐
274 tension is not .mli.
275 -intf-suffix string
277 Recognize file names ending with string as interface files (in‐
278 stead of the default .mli).
279 -keep-docs
281 Keep documentation strings in generated .cmi files.
282 -keep-locs
284 Keep locations in generated .cmi files.
285 -labels
287 Labels are not ignored in types, labels may be used in applica‐
288 tions, and labelled parameters can be given in any order. This
289 is the default.
290 -linkall
292 Force all modules contained in libraries to be linked in. If
293 this flag is not given, unreferenced modules are not linked in.
294 When building a library (option -a), setting the -linkall option
295 forces all subsequent links of programs involving that library
296 to link all the modules contained in the library. When compil‐
297 ing a module (option -c), setting the -linkall option ensures
298 that this module will always be linked if it is put in a library
299 and this library is linked.
300 -make-runtime
302 Build a custom runtime system (in the file specified by option
303 -o) incorporating the C object files and libraries given on the
304 command line. This custom runtime system can be used later to
305 execute bytecode executables produced with the option
306 ocamlc -use-runtime runtime-name.
307 -match-context-rows
309 Set number of rows of context used during pattern matching com‐
310 pilation. Lower values cause faster compilation, but less opti‐
311 mized code. The default value is 32.
312 -no-alias-deps
314 Do not record dependencies for module aliases.
315 -no-app-funct
317 Deactivates the applicative behaviour of functors. With this op‐
318 tion, each functor application generates new types in its result
319 and applying the same functor twice to the same argument yields
320 two incompatible structures.
321 -noassert
323 Do not compile assertion checks. Note that the special form as‐
324 sert false is always compiled because it is typed specially.
325 This flag has no effect when linking already-compiled files.
326 -noautolink
328 When linking .cma libraries, ignore -custom, -cclib and -ccopt
329 options potentially contained in the libraries (if these options
330 were given when building the libraries). This can be useful if
331 a library contains incorrect specifications of C libraries or C
332 options; in this case, during linking, set -noautolink and pass
333 the correct C libraries and options on the command line.
334 -nolabels
336 Ignore non-optional labels in types. Labels cannot be used in
337 applications, and parameter order becomes strict.
338 -nostdlib
340 Do not automatically add the standard library directory to the
341 list of directories searched for compiled interface files
342 (.cmi), compiled object code files (.cmo), libraries (.cma), and
343 C libraries specified with -cclib -lxxx . See also option -I.
344 -o exec-file
346 Specify the name of the output file produced by the linker. The
347 default output name is a.out, in keeping with the Unix tradi‐
348 tion. If the -a option is given, specify the name of the library
349 produced. If the -pack option is given, specify the name of the
350 packed object file produced. If the -output-obj option is
351 given, specify the name of the output file produced. This can
352 also be used when compiling an interface or implementation file,
353 without linking, in which case it sets the name of the cmi or
354 cmo file, and also sets the module name to the file name up to
355 the first dot.
356 -opaque
358 Interface file compiled with this option are marked so that
359 other compilation units depending on it will not rely on any im‐
360 plementation details of the compiled implementation. The native
361 compiler will not access the .cmx file of this unit -- nor warn
362 if it is absent. This can improve speed of compilation, for both
363 initial and incremental builds, at the expense of performance of
364 the generated code.
365 -open module
367 Opens the given module before processing the interface or imple‐
368 mentation files. If several -open options are given, they are
369 processed in order, just as if the statements open! module1;;
370 ... open! moduleN;; were added at the top of each file.
371 -output-obj
373 Cause the linker to produce a C object file instead of a byte‐
374 code executable file. This is useful to wrap OCaml code as a C
375 library, callable from any C program. The name of the output ob‐
376 ject file must be set with the -o option. This option can also
377 be used to produce a C source file (.c extension) or a compiled
378 shared/dynamic library (.so extension).
379 -pack Build a bytecode object file (.cmo file) and its associated com‐
381 piled interface (.cmi) that combines the object files given on
382 the command line, making them appear as sub-modules of the out‐
383 put .cmo file. The name of the output .cmo file must be given
384 with the -o option. For instance,
385 ocamlc -pack -o p.cmo a.cmo b.cmo c.cmo generates compiled files
386 p.cmo and p.cmi describing a compilation unit having three sub-
387 modules A, B and C, corresponding to the contents of the object
388 files a.cmo, b.cmo and c.cmo. These contents can be referenced
389 as P.A, P.B and P.C in the remainder of the program.
390 -pp command
392 Cause the compiler to call the given command as a preprocessor
393 for each source file. The output of command is redirected to an
394 intermediate file, which is compiled. If there are no compila‐
395 tion errors, the intermediate file is deleted afterwards. The
396 name of this file is built from the basename of the source file
397 with the extension .ppi for an interface (.mli) file and .ppo
398 for an implementation (.ml) file.
399 -ppx command
401 After parsing, pipe the abstract syntax tree through the pre‐
402 processor command. The module Ast_mapper(3) implements the ex‐
403 ternal interface of a preprocessor.
404 -principal
406 Check information path during type-checking, to make sure that
407 all types are derived in a principal way. When using labelled
408 arguments and/or polymorphic methods, this flag is required to
409 ensure future versions of the compiler will be able to infer
410 types correctly, even if internal algorithms change. All pro‐
411 grams accepted in -principal mode are also accepted in the de‐
412 fault mode with equivalent types, but different binary signa‐
413 tures, and this may slow down type checking; yet it is a good
414 idea to use it once before publishing source code.
415 -rectypes
417 Allow arbitrary recursive types during type-checking. By de‐
418 fault, only recursive types where the recursion goes through an
419 object type are supported. Note that once you have created an
420 interface using this flag, you must use it again for all depen‐
421 dencies.
422 -runtime-variant suffix
424 Add suffix to the name of the runtime library that will be used
425 by the program. If OCaml was configured with option -with-de‐
426 bug-runtime, then the d suffix is supported and gives a debug
427 version of the runtime.
428 -stop-after pass
430 Stop compilation after the given compilation pass. The currently
431 supported passes are: parsing, typing.
432 -safe-string
434 Enforce the separation between types string and bytes, thereby
435 making strings read-only. This is the default.
436 -short-paths
438 When a type is visible under several module-paths, use the
439 shortest one when printing the type's name in inferred inter‐
440 faces and error and warning messages.
441 -strict-sequence
443 Force the left-hand part of each sequence to have type unit.
444 -unboxed-types
446 When a type is unboxable (i.e. a record with a single argument
447 or a concrete datatype with a single constructor of one argu‐
448 ment) it will be unboxed unless annotated with [@@ocaml.boxed].
449 -no-unboxed-types
451 When a type is unboxable it will be boxed unless annotated with
452 [@@ocaml.unboxed]. This is the default.
453 -unsafe
455 Turn bound checking off for array and string accesses (the
456 v.(i)ands.[i] constructs). Programs compiled with -unsafe are
457 therefore slightly faster, but unsafe: anything can happen if
458 the program accesses an array or string outside of its bounds.
459 -unsafe-string
461 Identify the types string and bytes, thereby making strings
462 writable. This is intended for compatibility with old source
463 code and should not be used with new software.
464 -use-runtime runtime-name
466 Generate a bytecode executable file that can be executed on the
467 custom runtime system runtime-name, built earlier with
468 ocamlc -make-runtime runtime-name.
469 -v Print the version number of the compiler and the location of the
471 standard library directory, then exit.
472 -verbose
474 Print all external commands before they are executed, in partic‐
475 ular invocations of the C compiler and linker in -custom mode.
476 Useful to debug C library problems.
477 -vnum or -version
479 Print the version number of the compiler in short form (e.g.
480 "3.11.0"), then exit.
481 -w warning-list
483 Enable, disable, or mark as fatal the warnings specified by the
484 argument warning-list.
485 Each warning can be enabled or disabled, and each warning can be
487 fatal or non-fatal. If a warning is disabled, it isn't dis‐
488 played and doesn't affect compilation in any way (even if it is
489 fatal). If a warning is enabled, it is displayed normally by
490 the compiler whenever the source code triggers it. If it is en‐
491 abled and fatal, the compiler will also stop with an error after
492 displaying it.
493 The warning-list argument is a sequence of warning specifiers,
495 with no separators between them. A warning specifier is one of
496 the following:
497 +num Enable warning number num.
499 -num Disable warning number num.
501 @num Enable and mark as fatal warning number num.
503 +num1..num2 Enable all warnings between num1 and num2 (inclu‐
505 sive).
506 -num1..num2 Disable all warnings between num1 and num2 (inclu‐
508 sive).
509 @num1..num2 Enable and mark as fatal all warnings between num1
511 and num2 (inclusive).
512 +letter Enable the set of warnings corresponding to letter.
514 The letter may be uppercase or lowercase.
515 -letter Disable the set of warnings corresponding to letter.
517 The letter may be uppercase or lowercase.
518 @letter Enable and mark as fatal the set of warnings corre‐
520 sponding to letter. The letter may be uppercase or lowercase.
521 uppercase-letter Enable the set of warnings corresponding to
523 uppercase-letter.
524 lowercase-letter Disable the set of warnings corresponding to
526 lowercase-letter.
527 The warning numbers are as follows.
529 1 Suspicious-looking start-of-comment mark.
531 2 Suspicious-looking end-of-comment mark.
533 3 Deprecated feature.
535 4 Fragile pattern matching: matching that will remain com‐
537 plete even if additional constructors are added to one of the
538 variant types matched.
539 5 Partially applied function: expression whose result has
541 function type and is ignored.
542 6 Label omitted in function application.
544 7 Method overridden without using the "method!" keyword.
546 8 Partial match: missing cases in pattern-matching.
548 9 Missing fields in a record pattern.
550 10 Expression on the left-hand side of a sequence that doesn't
552 have type unit (and that is not a function, see warning number
553 5).
554 11 Redundant case in a pattern matching (unused match case).
556 12 Redundant sub-pattern in a pattern-matching.
558 13 Override of an instance variable.
560 14 Illegal backslash escape in a string constant.
562 15 Private method made public implicitly.
564 16 Unerasable optional argument.
566 17 Undeclared virtual method.
568 18 Non-principal type.
570 19 Type without principality.
572 20 Unused function argument.
574 21 Non-returning statement.
576 22 Preprocessor warning.
578 23 Useless record with clause.
580 24 Bad module name: the source file name is not a valid OCaml
582 module name.
583 25 Deprecated: now part of warning 8.
585 26 Suspicious unused variable: unused variable that is bound
587 with let or as, and doesn't start with an underscore (_) charac‐
588 ter.
589 27 Innocuous unused variable: unused variable that is not
591 bound with let nor as, and doesn't start with an underscore (_)
592 character.
593 28 A pattern contains a constant constructor applied to the
595 underscore (_) pattern.
596 29 A non-escaped end-of-line was found in a string constant.
598 This may cause portability problems between Unix and Windows.
599 30 Two labels or constructors of the same name are defined in
601 two mutually recursive types.
602 31 A module is linked twice in the same executable.
604 32 Unused value declaration.
606 33 Unused open statement.
608 34 Unused type declaration.
610 35 Unused for-loop index.
612 36 Unused ancestor variable.
614 37 Unused constructor.
616 38 Unused extension constructor.
618 39 Unused rec flag.
620 40 Constructor or label name used out of scope.
622 41 Ambiguous constructor or label name.
624 42 Disambiguated constructor or label name.
626 43 Nonoptional label applied as optional.
628 44 Open statement shadows an already defined identifier.
630 45 Open statement shadows an already defined label or con‐
632 structor.
633 46 Error in environment variable.
635 47 Illegal attribute payload.
637 48 Implicit elimination of optional arguments.
639 49 Missing cmi file when looking up module alias.
641 50 Unexpected documentation comment.
643 59 Assignment on non-mutable value.
645 60 Unused module declaration.
647 61 Unannotated unboxable type in primitive declaration.
649 62 Type constraint on GADT type declaration.
651 63 Erroneous printed signature.
653 64 -unsafe used with a preprocessor returning a syntax tree.
655 65 Type declaration defining a new '()' constructor.
657 66 Unused open! statement.
659 67 Unused functor parameter.
661 68 Pattern-matching depending on mutable state prevents the
663 remaining arguments from being uncurried.
664 The letters stand for the following sets of warnings. Any let‐
666 ter not mentioned here corresponds to the empty set.
667 A all warnings
669 C 1, 2
671 D 3
673 E 4
675 F 5
677 K 32, 33, 34, 35, 36, 37, 38, 39
679 L 6
681 M 7
683 P 8
685 R 9
687 S 10
689 U 11, 12
691 V 13
693 X 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30
695 Y 26
697 Z 27
699 The default setting is
702 -w +a-4-6-7-9-27-29-30-32..42-44-45-48-50-60-66-67-68. Note
703 that warnings 5 and 10 are not always triggered, depending on
704 the internals of the type checker.
705 -warn-error warning-list
707 Mark as errors the warnings specified in the argument warn‐
708 ing-list. The compiler will stop with an error when one of
709 these warnings is emitted. The warning-list has the same mean‐
710 ing as for the -w option: a + sign (or an uppercase letter)
711 marks the corresponding warnings as fatal, a - sign (or a lower‐
712 case letter) turns them back into non-fatal warnings, and a @
713 sign both enables and marks as fatal the corresponding warnings.
714 Note: it is not recommended to use the -warn-error option in
716 production code, because it will almost certainly prevent com‐
717 piling your program with later versions of OCaml when they add
718 new warnings or modify existing warnings.
719 The default setting is -warn-error -a+31 (only warning 31 is fa‐
721 tal).
722 -warn-help
724 Show the description of all available warning numbers.
725 -where Print the location of the standard library, then exit.
727 -with-runtime
729 Include the runtime system in the generated program. This is the
730 default.
731 -without-runtime
733 The compiler does not include the runtime system (nor a refer‐
734 ence to it) in the generated program; it must be supplied sepa‐
735 rately.
736 - file Process file as a file name, even if it starts with a dash (-)
738 character.
739 -help or --help
741 Display a short usage summary and exit.
742
745 ocamlopt(1), ocamlrun(1), ocaml(1).
746 The OCaml user's manual, chapter "Batch compilation".
747 OCAMLC(1)