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
41 object code file x.cmo. The file x.cmi produced corresponds to an
42 interface 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
69 libraries. 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
76 dynamically 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
86 directly, 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
91 native-code compiler ocamlopt(1). Thus, it behaves exactly like
92 ocamlc, but compiles faster. ocamlc.opt may not be available in all
93 installations 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.
109 Additionally, 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 Dump detailed information about the compilation (types, bind‐
115 ings, tail-calls, etc). The information for file src.ml is put
116 into file src.annot. In case of a type error, dump all the
117 information inferred by the type-checker before the error. The
118 src.annot file can be used with the emacs commands given in
119 emacs/caml-types.el to display types and other annotations
120 interactively.
121 -bin-annot
123 Dump detailed information about the compilation (types, bind‐
124 ings, tail-calls, etc) in binary format. The information for
125 file src.ml is put into file src.cmt. In case of a type error,
126 dump all the information inferred by the type-checker before the
127 error. The annotation files produced by -bin-annot contain more
128 information and are much more compact than the files produced by
129 -annot.
130 -c Compile only. Suppress the linking phase of the compilation.
132 Source code files are turned into compiled files, but no exe‐
133 cutable file is produced. This option is useful to compile mod‐
134 ules separately.
135 -cc ccomp
137 Use ccomp as the C linker when linking in "custom runtime" mode
138 (see the -custom option) and as the C compiler for compiling .c
139 source files.
140 -cclib -llibname
142 Pass the -llibname option to the C linker when linking in "cus‐
143 tom runtime" mode (see the -custom option). This causes the
144 given C library to be linked with the program.
145 -ccopt option
147 Pass the given option to the C compiler and linker, when linking
148 in "custom runtime" mode (see the -custom option). For instance,
149 -ccopt -Ldir causes the C linker to search for C libraries in
150 directory dir.
151 -color mode
153 Enable or disable colors in compiler messages (especially warn‐
154 ings and errors). The following modes are supported:
155 auto use heuristics to enable colors only if the output supports
157 them (an ANSI-compatible tty terminal);
158 always enable colors unconditionally;
160 never disable color output.
162 The default setting is auto, and the current heuristic checks
164 that the "TERM" environment variable exists and is not empty or
165 "dumb", and that isatty(stderr) holds.
166 The environment variable "OCAML_COLOR" is considered if -color
168 is not provided. Its values are auto/always/never as above.
169 -error-style mode
172 Control the way error messages and warnings are printed. The
173 following modes are supported:
174 short only print the error and its location;
176 contextual like "short", but also display the source code snip‐
178 pet corresponding to the location of the error.
179 The default setting is contextual.
181 The environment variable "OCAML_ERROR_STYLE" is considered if
183 -error-style is not provided. Its values are short/contextual as
184 above.
185 -compat-32
188 Check that the generated bytecode executable can run on 32-bit
189 platforms and signal an error if it cannot. This is useful when
190 compiling bytecode on a 64-bit machine.
191 -config
193 Print the version number of ocamlc(1) and a detailed summary of
194 its configuration, then exit.
195 -config-var
197 Print the value of a specific configuration variable from the
198 -config output, then exit. If the variable does not exist, the
199 exit code is non-zero.
200 -custom
202 Link in "custom runtime" mode. In the default linking mode, the
203 linker produces bytecode that is intended to be executed with
204 the shared runtime system, ocamlrun(1). In the custom runtime
205 mode, the linker produces an output file that contains both the
206 runtime system and the bytecode for the program. The resulting
207 file is larger, but it can be executed directly, even if the
208 ocamlrun(1) command is not installed. Moreover, the "custom run‐
209 time" mode enables linking OCaml code with user-defined C func‐
210 tions.
211 Never use the strip(1) command on executables produced by
213 ocamlc -custom, this would remove the bytecode part of the exe‐
214 cutable.
215 Security warning: never set the "setuid" or "setgid" bits on
217 executables produced by ocamlc -custom, this would make them
218 vulnerable to attacks.
219 -depend ocamldep-args
221 Compute dependencies, as ocamldep would do.
222 -dllib -llibname
224 Arrange for the C shared library dlllibname.so to be loaded
225 dynamically by the run-time system ocamlrun(1) at program start-
226 up time.
227 -dllpath dir
229 Adds the directory dir to the run-time search path for shared C
230 libraries. At link-time, shared libraries are searched in the
231 standard search path (the one corresponding to the -I option).
232 The -dllpath option simply stores dir in the produced executable
233 file, where ocamlrun(1) can find it and use it.
234 -for-pack module-path
236 Generate an object file (.cmo file) that can later be included
237 as a sub-module (with the given access path) of a compilation
238 unit constructed with -pack. For instance,
239 ocamlc -for-pack P -c A.ml will generate a.cmo that can later be
240 used with ocamlc -pack -o P.cmo a.cmo. Note: you can still pack
241 a module that was compiled without -for-pack but in this case
242 exceptions will be printed with the wrong names.
243 -g Add debugging information while compiling and linking. This
245 option is required in order to be able to debug the program with
246 ocamldebug(1) and to produce stack backtraces when the program
247 terminates on an uncaught exception.
248 -i Cause the compiler to print all defined names (with their
250 inferred types or their definitions) when compiling an implemen‐
251 tation (.ml file). No compiled files (.cmo and .cmi files) are
252 produced. This can be useful to check the types inferred by the
253 compiler. Also, since the output follows the syntax of inter‐
254 faces, it can help in writing an explicit interface (.mli file)
255 for a file: just redirect the standard output of the compiler to
256 a .mli file, and edit that file to remove all declarations of
257 unexported names.
258 -I directory
260 Add the given directory to the list of directories searched for
261 compiled interface files (.cmi), compiled object code files
262 (.cmo), libraries (.cma), and C libraries specified with
263 -cclib -lxxx . By default, the current directory is searched
264 first, then the standard library directory. Directories added
265 with -I are searched after the current directory, in the order
266 in which they were given on the command line, but before the
267 standard library directory. See also option -nostdlib.
268 If the given directory starts with +, it is taken relative to
270 the standard library directory. For instance, -I +compiler-libs
271 adds the subdirectory compiler-libs of the standard library to
272 the search path.
273 -impl filename
275 Compile the file filename as an implementation file, even if its
276 extension is not .ml.
277 -intf filename
279 Compile the file filename as an interface file, even if its
280 extension is not .mli.
281 -intf-suffix string
283 Recognize file names ending with string as interface files
284 (instead of the default .mli).
285 -keep-docs
287 Keep documentation strings in generated .cmi files.
288 -keep-locs
290 Keep locations in generated .cmi files.
291 -labels
293 Labels are not ignored in types, labels may be used in applica‐
294 tions, and labelled parameters can be given in any order. This
295 is the default.
296 -linkall
298 Force all modules contained in libraries to be linked in. If
299 this flag is not given, unreferenced modules are not linked in.
300 When building a library (option -a), setting the -linkall option
301 forces all subsequent links of programs involving that library
302 to link all the modules contained in the library. When compil‐
303 ing a module (option -c), setting the -linkall option ensures
304 that this module will always be linked if it is put in a library
305 and this library is linked.
306 -make-runtime
308 Build a custom runtime system (in the file specified by option
309 -o) incorporating the C object files and libraries given on the
310 command line. This custom runtime system can be used later to
311 execute bytecode executables produced with the option
312 ocamlc -use-runtime runtime-name.
313 -match-context-rows
315 Set number of rows of context used during pattern matching com‐
316 pilation. Lower values cause faster compilation, but less opti‐
317 mized code. The default value is 32.
318 -no-alias-deps
320 Do not record dependencies for module aliases.
321 -no-app-funct
323 Deactivates the applicative behaviour of functors. With this
324 option, each functor application generates new types in its
325 result and applying the same functor twice to the same argument
326 yields two incompatible structures.
327 -noassert
329 Do not compile assertion checks. Note that the special form
330 assert false is always compiled because it is typed specially.
331 This flag has no effect when linking already-compiled files.
332 -noautolink
334 When linking .cma libraries, ignore -custom, -cclib and -ccopt
335 options potentially contained in the libraries (if these options
336 were given when building the libraries). This can be useful if
337 a library contains incorrect specifications of C libraries or C
338 options; in this case, during linking, set -noautolink and pass
339 the correct C libraries and options on the command line.
340 -nolabels
342 Ignore non-optional labels in types. Labels cannot be used in
343 applications, and parameter order becomes strict.
344 -nostdlib
346 Do not automatically add the standard library directory to the
347 list of directories searched for compiled interface files
348 (.cmi), compiled object code files (.cmo), libraries (.cma), and
349 C libraries specified with -cclib -lxxx . See also option -I.
350 -o exec-file
352 Specify the name of the output file produced by the linker. The
353 default output name is a.out, in keeping with the Unix tradi‐
354 tion. If the -a option is given, specify the name of the library
355 produced. If the -pack option is given, specify the name of the
356 packed object file produced. If the -output-obj option is
357 given, specify the name of the output file produced. This can
358 also be used when compiling an interface or implementation file,
359 without linking, in which case it sets the name of the cmi or
360 cmo file, and also sets the module name to the file name up to
361 the first dot.
362 -opaque
364 Interface file compiled with this option are marked so that
365 other compilation units depending on it will not rely on any
366 implementation details of the compiled implementation. The
367 native compiler will not access the .cmx file of this unit --
368 nor warn if it is absent. This can improve speed of compilation,
369 for both initial and incremental builds, at the expense of per‐
370 formance of the generated code.
371 -open module
373 Opens the given module before processing the interface or imple‐
374 mentation files. If several -open options are given, they are
375 processed in order, just as if the statements open! module1;;
376 ... open! moduleN;; were added at the top of each file.
377 -output-obj
379 Cause the linker to produce a C object file instead of a byte‐
380 code executable file. This is useful to wrap OCaml code as a C
381 library, callable from any C program. The name of the output
382 object file must be set with the -o option. This option can also
383 be used to produce a C source file (.c extension) or a compiled
384 shared/dynamic library (.so extension).
385 -pack Build a bytecode object file (.cmo file) and its associated com‐
387 piled interface (.cmi) that combines the object files given on
388 the command line, making them appear as sub-modules of the out‐
389 put .cmo file. The name of the output .cmo file must be given
390 with the -o option. For instance,
391 ocamlc -pack -o p.cmo a.cmo b.cmo c.cmo generates compiled files
392 p.cmo and p.cmi describing a compilation unit having three sub-
393 modules A, B and C, corresponding to the contents of the object
394 files a.cmo, b.cmo and c.cmo. These contents can be referenced
395 as P.A, P.B and P.C in the remainder of the program.
396 -plugin plugin
398 Dynamically load the code of the given plugin (a .cmo, .cma or
399 .cmxs file) in the compiler. The plugin must exist in the same
400 kind of code as the compiler (ocamlc.byte must load bytecode
401 plugins, while ocamlc.opt must load native code plugins), and
402 extension adaptation is done automatically for .cma files (to
403 .cmxs files if the compiler is compiled in native code).
404 -pp command
406 Cause the compiler to call the given command as a preprocessor
407 for each source file. The output of command is redirected to an
408 intermediate file, which is compiled. If there are no compila‐
409 tion errors, the intermediate file is deleted afterwards. The
410 name of this file is built from the basename of the source file
411 with the extension .ppi for an interface (.mli) file and .ppo
412 for an implementation (.ml) file.
413 -ppx command
415 After parsing, pipe the abstract syntax tree through the pre‐
416 processor command. The module Ast_mapper(3) implements the
417 external interface of a preprocessor.
418 -principal
420 Check information path during type-checking, to make sure that
421 all types are derived in a principal way. When using labelled
422 arguments and/or polymorphic methods, this flag is required to
423 ensure future versions of the compiler will be able to infer
424 types correctly, even if internal algorithms change. All pro‐
425 grams accepted in -principal mode are also accepted in the
426 default mode with equivalent types, but different binary signa‐
427 tures, and this may slow down type checking; yet it is a good
428 idea to use it once before publishing source code.
429 -rectypes
431 Allow arbitrary recursive types during type-checking. By
432 default, only recursive types where the recursion goes through
433 an object type are supported. Note that once you have created an
434 interface using this flag, you must use it again for all depen‐
435 dencies.
436 -runtime-variant suffix
438 Add suffix to the name of the runtime library that will be used
439 by the program. If OCaml was configured with option
440 -with-debug-runtime, then the d suffix is supported and gives a
441 debug version of the runtime.
442 -stop-after pass
444 Stop compilation after the given compilation pass. The currently
445 supported passes are: parsing, typing.
446 -safe-string
448 Enforce the separation between types string and bytes, thereby
449 making strings read-only. This is the default.
450 -short-paths
452 When a type is visible under several module-paths, use the
453 shortest one when printing the type's name in inferred inter‐
454 faces and error and warning messages.
455 -strict-sequence
457 Force the left-hand part of each sequence to have type unit.
458 -unboxed-types
460 When a type is unboxable (i.e. a record with a single argument
461 or a concrete datatype with a single constructor of one argu‐
462 ment) it will be unboxed unless annotated with [@@ocaml.boxed].
463 -no-unboxed-types
465 When a type is unboxable it will be boxed unless annotated with
466 [@@ocaml.unboxed]. This is the default.
467 -unsafe
469 Turn bound checking off for array and string accesses (the
470 v.(i)ands.[i] constructs). Programs compiled with -unsafe are
471 therefore slightly faster, but unsafe: anything can happen if
472 the program accesses an array or string outside of its bounds.
473 -unsafe-string
475 Identify the types string and bytes, thereby making strings
476 writable. This is intended for compatibility with old source
477 code and should not be used with new software.
478 -use-runtime runtime-name
480 Generate a bytecode executable file that can be executed on the
481 custom runtime system runtime-name, built earlier with
482 ocamlc -make-runtime runtime-name.
483 -v Print the version number of the compiler and the location of the
485 standard library directory, then exit.
486 -verbose
488 Print all external commands before they are executed, in partic‐
489 ular invocations of the C compiler and linker in -custom mode.
490 Useful to debug C library problems.
491 -vmthread
493 Deprecated since OCaml 4.08.0. Compile or link multithreaded
494 programs, in combination with the VM-level threads library
495 described in The OCaml user's manual.
496 -vnum or -version
498 Print the version number of the compiler in short form (e.g.
499 "3.11.0"), then exit.
500 -w warning-list
502 Enable, disable, or mark as fatal the warnings specified by the
503 argument warning-list.
504 Each warning can be enabled or disabled, and each warning can be
506 fatalor non-fatal. If a warning is disabled, it isn't displayed
507 and doesn't affect compilation in any way (even if it is fatal).
508 If a warning is enabled, it is displayed normally by the com‐
509 piler whenever the source code triggers it. If it is enabled
510 and fatal, the compiler will also stop with an error after dis‐
511 playing it.
512 The warning-list argument is a sequence of warning specifiers,
514 with no separators between them. A warning specifier is one of
515 the following:
516 +num Enable warning number num.
518 -num Disable warning number num.
520 @num Enable and mark as fatal warning number num.
522 +num1..num2 Enable all warnings between num1 and num2 (inclu‐
524 sive).
525 -num1..num2 Disable all warnings between num1 and num2 (inclu‐
527 sive).
528 @num1..num2 Enable and mark as fatal all warnings between num1
530 and num2 (inclusive).
531 +letter Enable the set of warnings corresponding to letter.
533 The letter may be uppercase or lowercase.
534 -letter Disable the set of warnings corresponding to letter.
536 The letter may be uppercase or lowercase.
537 @letter Enable and mark as fatal the set of warnings corre‐
539 sponding to letter. The letter may be uppercase or lowercase.
540 uppercase-letter Enable the set of warnings corresponding to
542 uppercase-letter.
543 lowercase-letter Disable the set of warnings corresponding to
545 lowercase-letter.
546 The warning numbers are as follows.
548 1 Suspicious-looking start-of-comment mark.
550 2 Suspicious-looking end-of-comment mark.
552 3 Deprecated feature.
554 4 Fragile pattern matching: matching that will remain com‐
556 plete even if additional constructors are added to one of the
557 variant types matched.
558 5 Partially applied function: expression whose result has
560 function type and is ignored.
561 6 Label omitted in function application.
563 7 Method overridden without using the "method!" keyword
565 8 Partial match: missing cases in pattern-matching.
567 9 Missing fields in a record pattern.
569 10 Expression on the left-hand side of a sequence that doesn't
571 have type unit (and that is not a function, see warning number
572 5).
573 11 Redundant case in a pattern matching (unused match case).
575 12 Redundant sub-pattern in a pattern-matching.
577 13 Override of an instance variable.
579 14 Illegal backslash escape in a string constant.
581 15 Private method made public implicitly.
583 16 Unerasable optional argument.
585 17 Undeclared virtual method.
587 18 Non-principal type.
589 19 Type without principality.
591 20 Unused function argument.
593 21 Non-returning statement.
595 22 Preprocessor warning.
597 23 Useless record with clause.
599 24 Bad module name: the source file name is not a valid OCaml
601 module name.
602 25 Deprecated: now part of warning 8.
604 26 Suspicious unused variable: unused variable that is bound
606 with let or as, and doesn't start with an underscore (_) charac‐
607 ter.
608 27 Innocuous unused variable: unused variable that is not
610 bound with let nor as, and doesn't start with an underscore (_)
611 character.
612 28 A pattern contains a constant constructor applied to the
614 underscore (_) pattern.
615 29 A non-escaped end-of-line was found in a string constant.
617 This may cause portability problems between Unix and Windows.
618 30 Two labels or constructors of the same name are defined in
620 two mutually recursive types.
621 31 A module is linked twice in the same executable.
623 32 Unused value declaration.
625 33 Unused open statement.
627 34 Unused type declaration.
629 35 Unused for-loop index.
631 36 Unused ancestor variable.
633 37 Unused constructor.
635 38 Unused extension constructor.
637 39 Unused rec flag.
639 40 Constructor or label name used out of scope.
641 41 Ambiguous constructor or label name.
643 42 Disambiguated constructor or label name.
645 43 Nonoptional label applied as optional.
647 44 Open statement shadows an already defined identifier.
649 45 Open statement shadows an already defined label or con‐
651 structor.
652 46 Error in environment variable.
654 47 Illegal attribute payload.
656 48 Implicit elimination of optional arguments.
658 49 Missing cmi file when looking up module alias.
660 50 Unexpected documentation comment.
662 59 Assignment on non-mutable value.
664 60 Unused module declaration.
666 61 Unannotated unboxable type in primitive declaration.
668 62 Type constraint on GADT type declaration
670 63 Erroneous printed signature
672 64 -unsafe used with a preprocessor returning a syntax tree
674 65 Type declaration defining a new '()' constructor
676 66 Unused open! statement.
678 The letters stand for the following sets of warnings. Any let‐
680 ter not mentioned here corresponds to the empty set.
681 A all warnings
683 C 1, 2
685 D 3
687 E 4
689 F 5
691 K 32, 33, 34, 35, 36, 37, 38, 39
693 L 6
695 M 7
697 P 8
699 R 9
701 S 10
703 U 11, 12
705 V 13
707 X 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30
709 Y 26
711 Z 27
713 The default setting is
716 -w +a-4-6-7-9-27-29-32..42-44-45-48-50-60-66. Note that warn‐
717 ings 5 and 10 are not always triggered, depending on the inter‐
718 nals of the type checker.
719 -warn-error warning-list
721 Mark as errors the warnings specified in the argument warn‐
722 ing-list. The compiler will stop with an error when one of
723 these warnings is emitted. The warning-list has the same mean‐
724 ing as for the -w option: a + sign (or an uppercase letter)
725 marks the corresponding warnings as fatal, a - sign (or a lower‐
726 case letter) turns them back into non-fatal warnings, and a @
727 sign both enables and marks as fatal the corresponding warnings.
728 Note: it is not recommended to use the -warn-error option in
730 production code, because it will almost certainly prevent com‐
731 piling your program with later versions of OCaml when they add
732 new warnings or modify existing warnings.
733 The default setting is -warn-error -a+31 (only warning 31 is
735 fatal).
736 -warn-help
738 Show the description of all available warning numbers.
739 -where Print the location of the standard library, then exit.
741 - file Process file as a file name, even if it starts with a dash (-)
743 character.
744 -help or --help
746 Display a short usage summary and exit.
747
750 ocamlopt(1), ocamlrun(1), ocaml(1).
751 The OCaml user's manual, chapter "Batch compilation".
752 OCAMLC(1)