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 or -output-com‐
351 plete-obj option is given, specify the name of the output file
352 produced. This can also be used when compiling an interface or
353 implementation file, without linking, in which case it sets the
354 name of the cmi or cmo file, and also sets the module name to
355 the file name up to 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 -output-complete-obj
381 Same as -output-obj except when creating an object file where it
382 includes the runtime and autolink libraries.
383 -pack Build a bytecode object file (.cmo file) and its associated com‐
385 piled interface (.cmi) that combines the object files given on
386 the command line, making them appear as sub-modules of the out‐
387 put .cmo file. The name of the output .cmo file must be given
388 with the -o option. For instance,
389 ocamlc -pack -o p.cmo a.cmo b.cmo c.cmo generates compiled files
390 p.cmo and p.cmi describing a compilation unit having three sub-
391 modules A, B and C, corresponding to the contents of the object
392 files a.cmo, b.cmo and c.cmo. These contents can be referenced
393 as P.A, P.B and P.C in the remainder of the program.
394 -pp command
396 Cause the compiler to call the given command as a preprocessor
397 for each source file. The output of command is redirected to an
398 intermediate file, which is compiled. If there are no compila‐
399 tion errors, the intermediate file is deleted afterwards. The
400 name of this file is built from the basename of the source file
401 with the extension .ppi for an interface (.mli) file and .ppo
402 for an implementation (.ml) file.
403 -ppx command
405 After parsing, pipe the abstract syntax tree through the pre‐
406 processor command. The module Ast_mapper(3) implements the ex‐
407 ternal interface of a preprocessor.
408 -principal
410 Check information path during type-checking, to make sure that
411 all types are derived in a principal way. When using labelled
412 arguments and/or polymorphic methods, this flag is required to
413 ensure future versions of the compiler will be able to infer
414 types correctly, even if internal algorithms change. All pro‐
415 grams accepted in -principal mode are also accepted in the de‐
416 fault mode with equivalent types, but different binary signa‐
417 tures, and this may slow down type checking; yet it is a good
418 idea to use it once before publishing source code.
419 -rectypes
421 Allow arbitrary recursive types during type-checking. By de‐
422 fault, only recursive types where the recursion goes through an
423 object type are supported. Note that once you have created an
424 interface using this flag, you must use it again for all depen‐
425 dencies.
426 -runtime-variant suffix
428 Add suffix to the name of the runtime library that will be used
429 by the program. If OCaml was configured with option -with-de‐
430 bug-runtime, then the d suffix is supported and gives a debug
431 version of the runtime.
432 -stop-after pass
434 Stop compilation after the given compilation pass. The currently
435 supported passes are: parsing, typing.
436 -safe-string
438 Enforce the separation between types string and bytes, thereby
439 making strings read-only. This is the default.
440 -short-paths
442 When a type is visible under several module-paths, use the
443 shortest one when printing the type's name in inferred inter‐
444 faces and error and warning messages.
445 -strict-sequence
447 Force the left-hand part of each sequence to have type unit.
448 -unboxed-types
450 When a type is unboxable (i.e. a record with a single argument
451 or a concrete datatype with a single constructor of one argu‐
452 ment) it will be unboxed unless annotated with [@@ocaml.boxed].
453 -no-unboxed-types
455 When a type is unboxable it will be boxed unless annotated with
456 [@@ocaml.unboxed]. This is the default.
457 -unsafe
459 Turn bound checking off for array and string accesses (the
460 v.(i)ands.[i] constructs). Programs compiled with -unsafe are
461 therefore slightly faster, but unsafe: anything can happen if
462 the program accesses an array or string outside of its bounds.
463 -unsafe-string
465 Identify the types string and bytes, thereby making strings
466 writable. This is intended for compatibility with old source
467 code and should not be used with new software.
468 -use-runtime runtime-name
470 Generate a bytecode executable file that can be executed on the
471 custom runtime system runtime-name, built earlier with
472 ocamlc -make-runtime runtime-name.
473 -v Print the version number of the compiler and the location of the
475 standard library directory, then exit.
476 -verbose
478 Print all external commands before they are executed, in partic‐
479 ular invocations of the C compiler and linker in -custom mode.
480 Useful to debug C library problems.
481 -vnum or -version
483 Print the version number of the compiler in short form (e.g.
484 "3.11.0"), then exit.
485 -w warning-list
487 Enable, disable, or mark as fatal the warnings specified by the
488 argument warning-list.
489 Each warning can be enabled or disabled, and each warning can be
491 fatal or non-fatal. If a warning is disabled, it isn't dis‐
492 played and doesn't affect compilation in any way (even if it is
493 fatal). If a warning is enabled, it is displayed normally by
494 the compiler whenever the source code triggers it. If it is en‐
495 abled and fatal, the compiler will also stop with an error after
496 displaying it.
497 The warning-list argument is a sequence of warning specifiers,
499 with no separators between them. A warning specifier is one of
500 the following:
501 +num Enable warning number num.
503 -num Disable warning number num.
505 @num Enable and mark as fatal warning number num.
507 +num1..num2 Enable all warnings between num1 and num2 (inclu‐
509 sive).
510 -num1..num2 Disable all warnings between num1 and num2 (inclu‐
512 sive).
513 @num1..num2 Enable and mark as fatal all warnings between num1
515 and num2 (inclusive).
516 +letter Enable the set of warnings corresponding to letter.
518 The letter may be uppercase or lowercase.
519 -letter Disable the set of warnings corresponding to letter.
521 The letter may be uppercase or lowercase.
522 @letter Enable and mark as fatal the set of warnings corre‐
524 sponding to letter. The letter may be uppercase or lowercase.
525 uppercase-letter Enable the set of warnings corresponding to
527 uppercase-letter.
528 lowercase-letter Disable the set of warnings corresponding to
530 lowercase-letter.
531 The warning numbers are as follows.
533 1 Suspicious-looking start-of-comment mark.
535 2 Suspicious-looking end-of-comment mark.
537 3 Deprecated feature.
539 4 Fragile pattern matching: matching that will remain com‐
541 plete even if additional constructors are added to one of the
542 variant types matched.
543 5 Partially applied function: expression whose result has
545 function type and is ignored.
546 6 Label omitted in function application.
548 7 Method overridden without using the "method!" keyword.
550 8 Partial match: missing cases in pattern-matching.
552 9 Missing fields in a record pattern.
554 10 Expression on the left-hand side of a sequence that doesn't
556 have type unit (and that is not a function, see warning number
557 5).
558 11 Redundant case in a pattern matching (unused match case).
560 12 Redundant sub-pattern in a pattern-matching.
562 13 Override of an instance variable.
564 14 Illegal backslash escape in a string constant.
566 15 Private method made public implicitly.
568 16 Unerasable optional argument.
570 17 Undeclared virtual method.
572 18 Non-principal type.
574 19 Type without principality.
576 20 Unused function argument.
578 21 Non-returning statement.
580 22 Preprocessor warning.
582 23 Useless record with clause.
584 24 Bad module name: the source file name is not a valid OCaml
586 module name.
587 25 Deprecated: now part of warning 8.
589 26 Suspicious unused variable: unused variable that is bound
591 with let or as, and doesn't start with an underscore (_) charac‐
592 ter.
593 27 Innocuous unused variable: unused variable that is not
595 bound with let nor as, and doesn't start with an underscore (_)
596 character.
597 28 A pattern contains a constant constructor applied to the
599 underscore (_) pattern.
600 29 A non-escaped end-of-line was found in a string constant.
602 This may cause portability problems between Unix and Windows.
603 30 Two labels or constructors of the same name are defined in
605 two mutually recursive types.
606 31 A module is linked twice in the same executable.
608 32 Unused value declaration.
610 33 Unused open statement.
612 34 Unused type declaration.
614 35 Unused for-loop index.
616 36 Unused ancestor variable.
618 37 Unused constructor.
620 38 Unused extension constructor.
622 39 Unused rec flag.
624 40 Constructor or label name used out of scope.
626 41 Ambiguous constructor or label name.
628 42 Disambiguated constructor or label name.
630 43 Nonoptional label applied as optional.
632 44 Open statement shadows an already defined identifier.
634 45 Open statement shadows an already defined label or con‐
636 structor.
637 46 Error in environment variable.
639 47 Illegal attribute payload.
641 48 Implicit elimination of optional arguments.
643 49 Missing cmi file when looking up module alias.
645 50 Unexpected documentation comment.
647 59 Assignment on non-mutable value.
649 60 Unused module declaration.
651 61 Unannotated unboxable type in primitive declaration.
653 62 Type constraint on GADT type declaration.
655 63 Erroneous printed signature.
657 64 -unsafe used with a preprocessor returning a syntax tree.
659 65 Type declaration defining a new '()' constructor.
661 66 Unused open! statement.
663 67 Unused functor parameter.
665 68 Pattern-matching depending on mutable state prevents the
667 remaining arguments from being uncurried.
668 The letters stand for the following sets of warnings. Any let‐
670 ter not mentioned here corresponds to the empty set.
671 A all warnings
673 C 1, 2
675 D 3
677 E 4
679 F 5
681 K 32, 33, 34, 35, 36, 37, 38, 39
683 L 6
685 M 7
687 P 8
689 R 9
691 S 10
693 U 11, 12
695 V 13
697 X 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30
699 Y 26
701 Z 27
703 The default setting is
706 -w +a-4-7-9-27-29-30-32..42-44-45-48-50-60-66..70. Note that
707 warnings 5 and 10 are not always triggered, depending on the in‐
708 ternals of the type checker.
709 -warn-error warning-list
711 Mark as errors the warnings specified in the argument warn‐
712 ing-list. The compiler will stop with an error when one of
713 these warnings is emitted. The warning-list has the same mean‐
714 ing as for the -w option: a + sign (or an uppercase letter)
715 marks the corresponding warnings as fatal, a - sign (or a lower‐
716 case letter) turns them back into non-fatal warnings, and a @
717 sign both enables and marks as fatal the corresponding warnings.
718 Note: it is not recommended to use the -warn-error option in
720 production code, because it will almost certainly prevent com‐
721 piling your program with later versions of OCaml when they add
722 new warnings or modify existing warnings.
723 The default setting is -warn-error -a+31 (only warning 31 is fa‐
725 tal).
726 -warn-help
728 Show the description of all available warning numbers.
729 -where Print the location of the standard library, then exit.
731 -with-runtime
733 Include the runtime system in the generated program. This is the
734 default.
735 -without-runtime
737 The compiler does not include the runtime system (nor a refer‐
738 ence to it) in the generated program; it must be supplied sepa‐
739 rately.
740 - file Process file as a file name, even if it starts with a dash (-)
742 character.
743 -help or --help
745 Display a short usage summary and exit.
746
749 ocamlopt(1), ocamlrun(1), ocaml(1).
750 The OCaml user's manual, chapter "Batch compilation".
751 OCAMLC(1)