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NAME

       ocamlc - The OCaml bytecode compiler

SYNOPSIS

       ocamlc [ options ] filename ...

       ocamlc.opt [ options ] filename ...

DESCRIPTION

       The  OCaml  bytecode  compiler  ocamlc(1)  compiles OCaml source files to bytecode object files and links
       these object files to produce standalone bytecode executable files.  These executable files are then  run
       by the bytecode interpreter ocamlrun(1).

       The  ocamlc(1)  command  has  a command-line interface similar to the one of most C compilers. It accepts
       several types of arguments and processes them sequentially:

       Arguments ending in .mli are taken to be source files for compilation unit interfaces. Interfaces specify
       the  names  exported  by compilation units: they declare value names with their types, define public data
       types, declare abstract data types, and so on. From the file x.mli, the  ocamlc(1)  compiler  produces  a
       compiled interface in the file x.cmi.

       Arguments   ending   in  .ml  are  taken  to  be  source  files  for  compilation  unit  implementations.
       Implementations provide definitions for the names exported by the unit, and also contain  expressions  to
       be evaluated for their side-effects.  From the file x.ml, the ocamlc(1) compiler produces compiled object
       bytecode in the file x.cmo.

       If the interface file x.mli exists, the implementation x.ml is checked against the corresponding compiled
       interface  x.cmi,  which  is assumed to exist. If no interface x.mli is provided, the compilation of x.ml
       produces a compiled interface file x.cmi in addition to the compiled object code file  x.cmo.   The  file
       x.cmi  produced corresponds to an interface that exports everything that is defined in the implementation
       x.ml.

       Arguments ending in .cmo are taken to be compiled object bytecode.   These  files  are  linked  together,
       along with the object files obtained by compiling .ml arguments (if any), and the OCaml standard library,
       to produce a standalone executable program. The order in which .cmo and.ml arguments are presented on the
       command  line is relevant: compilation units are initialized in that order at run-time, and it is a link-
       time error to use a component of a unit before having initialized it. Hence, a given x.cmo file must come
       before all .cmo files that refer to the unit x.

       Arguments  ending  in  .cma  are  taken to be libraries of object bytecode.  A library of object bytecode
       packs in a single file a set of object bytecode files (.cmo files). Libraries are  built  with  ocamlc -a
       (see  the  description  of  the -a option below). The object files contained in the library are linked as
       regular .cmo files (see above), in the order specified when the .cma file was built. The only  difference
       is  that  if  an object file contained in a library is not referenced anywhere in the program, then it is
       not linked in.

       Arguments ending in .c are passed to the C compiler, which generates a .o object file. This  object  file
       is linked with the program if the -custom flag is set (see the description of -custom below).

       Arguments  ending  in  .o  or .a are assumed to be C object files and libraries. They are passed to the C
       linker when linking in -custom mode (see the description of -custom below).

       Arguments ending in .so are assumed to be C shared libraries (DLLs).  During linking, they  are  searched
       for  external  C  functions  referenced from the OCaml code, and their names are written in the generated
       bytecode executable.  The run-time system ocamlrun(1) then loads them  dynamically  at  program  start-up
       time.

       The  output of the linking phase is a file containing compiled bytecode that can be executed by the OCaml
       bytecode interpreter: the command ocamlrun(1).  If caml.out is the name  of  the  file  produced  by  the
       linking  phase, the command ocamlrun caml.out arg1  arg2 ... argn executes the compiled code contained in
       caml.out, passing it as arguments the  character  strings  arg1  to  argn.   (See  ocamlrun(1)  for  more
       details.)

       On  most  systems,  the  file  produced  by  the  linking  phase  can  be run directly, as in: ./caml.out
       arg1  arg2 ... argn.  The produced file has the executable bit set, and it manages to launch the bytecode
       interpreter by itself.

       ocamlc.opt is the same compiler as ocamlc, but compiled with the native-code compiler ocamlopt(1).  Thus,
       it behaves  exactly  like  ocamlc,  but  compiles  faster.   ocamlc.opt  may  not  be  available  in  all
       installations of OCaml.

OPTIONS

       The following command-line options are recognized by ocamlc(1).

       -a     Build  a library (.cma file) with the object files (.cmo files) given on the command line, instead
              of linking them into an executable file. The name of the library must be set with the -o option.

              If -custom, -cclib or -ccopt options are passed on the command line, these options are  stored  in
              the  resulting  .cma  library.   Then,  linking  with  this  library  automatically  adds back the
              -custom, -cclib and -ccopt options as if they had been provided on the command  line,  unless  the
              -noautolink  option  is given. Additionally, a substring $CAMLORIGIN inside a  -ccopt options will
              be replaced by the full path to the .cma library, excluding the filename.  -absname Show  absolute
              filenames in error messages.

       -annot Dump  detailed  information  about  the  compilation  (types,  bindings,  tail-calls,  etc).   The
              information for file src.ml is put into file src.annot.  In case of a type  error,  dump  all  the
              information inferred by the type-checker before the error. The src.annot file can be used with the
              emacs commands given in emacs/caml-types.el to display types and other annotations interactively.

       -bin-annot
              Dump detailed information about the compilation  (types,  bindings,  tail-calls,  etc)  in  binary
              format.  The  information for file src.ml is put into file src.cmt.  In case of a type error, dump
              all the information inferred by the type-checker before the error.  The annotation files  produced
              by  -bin-annot  contain  more  information  and  are  much more compact than the files produced by
              -annot.

       -c     Compile only. Suppress the linking phase of the compilation. Source code  files  are  turned  into
              compiled  files,  but  no  executable  file  is produced. This option is useful to compile modules
              separately.

       -cc ccomp
              Use ccomp as the C linker when linking in "custom runtime" mode (see the -custom  option)  and  as
              the C compiler for compiling .c source files.

       -cclib -llibname
              Pass  the  -llibname option to the C linker when linking in "custom runtime" mode (see the -custom
              option). This causes the given C library to be linked with the program.

       -ccopt option
              Pass the given option to the C compiler and linker, when linking in "custom runtime" mode (see the
              -custom  option).  For  instance,  -ccopt -Ldir  causes  the C linker to search for C libraries in
              directory dir.

       -compat-32
              Check that the generated bytecode executable can run on 32-bit platforms and signal an error if it
              cannot. This is useful when compiling bytecode on a 64-bit machine.

       -config
              Print the version number of ocamlc(1) and a detailed summary of its configuration, then exit.

       -custom
              Link  in  "custom runtime" mode. In the default linking mode, the linker produces bytecode that is
              intended to be executed with the shared runtime system, ocamlrun(1).  In the custom runtime  mode,
              the  linker produces an output file that contains both the runtime system and the bytecode for the
              program. The resulting file is larger, but it can be executed directly, even  if  the  ocamlrun(1)
              command  is  not  installed.  Moreover,  the "custom runtime" mode enables linking OCaml code with
              user-defined C functions.

              Never use the strip(1) command on executables produced by ocamlc -custom, this  would  remove  the
              bytecode part of the executable.

       -dllib -llibname
              Arrange  for  the  C  shared library dlllibname.so to be loaded dynamically by the run-time system
              ocamlrun(1) at program start-up time.

       -dllpath dir
              Adds the directory dir to the run-time search path for shared C libraries.  At  link-time,  shared
              libraries  are searched in the standard search path (the one corresponding to the -I option).  The
              -dllpath option simply stores dir in the produced executable file, where ocamlrun(1) can  find  it
              and use it.

       -for-pack ident
              This option is accepted for compatibility with ocamlopt(1) ; it does nothing.

       -g     Add debugging information while compiling and linking. This option is required in order to be able
              to debug the program  with  ocamldebug(1)  and  to  produce  stack  backtraces  when  the  program
              terminates on an uncaught exception.

       -i     Cause  the  compiler  to  print all defined names (with their inferred types or their definitions)
              when compiling an implementation (.ml file). No compiled files (.cmo and .cmi files) are produced.
              This can be useful to check the types inferred by the compiler. Also, since the output follows the
              syntax of interfaces, it can help in writing an explicit interface (.mli file) for  a  file:  just
              redirect  the  standard  output  of  the compiler to a .mli file, and edit that file to remove all
              declarations of unexported names.

       -I directory
              Add the given directory to the list of directories searched for compiled interface  files  (.cmi),
              compiled object code files (.cmo), libraries (.cma), and C libraries specified with -cclib -lxxx .
              By default, the current  directory  is  searched  first,  then  the  standard  library  directory.
              Directories  added  with  -I  are searched after the current directory, in the order in which they
              were given on the command line, but  before  the  standard  library  directory.  See  also  option
              -nostdlib.

              If  the given directory starts with +, it is taken relative to the standard library directory. For
              instance, -I +compiler-libs adds the subdirectory compiler-libs of the  standard  library  to  the
              search path.

       -impl filename
              Compile the file filename as an implementation file, even if its extension is not .ml.

       -intf filename
              Compile the file filename as an interface file, even if its extension is not .mli.

       -intf-suffix string
              Recognize file names ending with string as interface files (instead of the default .mli).

       -keep-docs
              Keep documentation strings in generated .cmi files.

       -keep-locs
              Keep locations in generated .cmi files.

       -labels
              Labels  are  not ignored in types, labels may be used in applications, and labelled parameters can
              be given in any order.  This is the default.

       -linkall
              Force all modules contained in libraries to be linked in. If this flag is not given,  unreferenced
              modules are not linked in. When building a library (option -a), setting the -linkall option forces
              all subsequent links of programs involving that library to link all the modules contained  in  the
              library.

       -make-runtime
              Build  a  custom  runtime  system  (in the file specified by option -o) incorporating the C object
              files and libraries given on the command line.  This custom runtime system can be  used  later  to
              execute bytecode executables produced with the option ocamlc -use-runtime runtime-name.

       -no-alias-deps
              Do not record dependencies for module aliases.

       -no-app-funct
              Deactivates  the  applicative  behaviour  of  functors. With this option, each functor application
              generates new types in its result and applying the same functor twice to the same argument  yields
              two incompatible structures.

       -noassert
              Do  not  compile  assertion  checks.   Note  that the special form assert false is always compiled
              because it is typed specially.  This flag has no effect when linking already-compiled files.

       -noautolink
              When linking .cma libraries, ignore -custom, -cclib and -ccopt options  potentially  contained  in
              the  libraries (if these options were given when building the libraries).  This can be useful if a
              library contains incorrect specifications of C libraries  or  C  options;  in  this  case,  during
              linking, set -noautolink and pass the correct C libraries and options on the command line.

       -nolabels
              Ignore  non-optional  labels  in types. Labels cannot be used in applications, and parameter order
              becomes strict.

       -nostdlib
              Do not automatically add the standard library directory to the list of  directories  searched  for
              compiled  interface  files  (.cmi),  compiled  object  code  files (.cmo), libraries (.cma), and C
              libraries specified with -cclib -lxxx .  See also option -I.

       -o exec-file
              Specify the name of the output file produced by the linker. The default output name is  a.out,  in
              keeping  with  the  Unix  tradition.  If  the  -a option is given, specify the name of the library
              produced.  If the -pack option is given, specify the name of the packed object file produced.   If
              the  -output-obj  option is given, specify the name of the output file produced.  This can also be
              used when compiling an interface or implementation file, without linking, in which  case  it  sets
              the  name  of  the cmi or cmo file, and also sets the module name to the file name up to the first
              dot.

       -open module
              Opens the given module before processing the interface or implementation files. If  several  -open
              options  are  given,  they  are  processed in order, just as if the statements open! module1;; ...
              open! moduleN;; were added at the top of each file.

       -output-obj
              Cause the linker to produce a C object file instead of a bytecode executable file. This is  useful
              to wrap OCaml code as a C library, callable from any C program. The name of the output object file
              must be set with the -o option. This option can also be used  to  produce  a  C  source  file  (.c
              extension) or a compiled shared/dynamic library (.so extension).

       -pack  Build  a  bytecode  object  file  (.cmo  file)  and  its associated compiled interface (.cmi) that
              combines the object files given on the command line, making them  appear  as  sub-modules  of  the
              output  .cmo  file.   The  name  of  the  output  .cmo file must be given with the -o option.  For
              instance,  ocamlc -pack -o p.cmo a.cmo b.cmo c.cmo  generates  compiled  files  p.cmo  and   p.cmi
              describing  a  compilation unit having three sub-modules A, B and C, corresponding to the contents
              of the object files a.cmo, b.cmo and c.cmo.  These contents can be referenced as P.A, P.B and  P.C
              in the remainder of the program.

       -pp command
              Cause the compiler to call the given command as a preprocessor for each source file. The output of
              command is redirected to an intermediate file, which is compiled.  If  there  are  no  compilation
              errors,  the  intermediate  file  is  deleted  afterwards. The name of this file is built from the
              basename of the source file with the extension .ppi for an interface (.mli) file and .ppo  for  an
              implementation (.ml) file.

       -ppx command
              After  parsing,  pipe  the  abstract  syntax  tree  through  the preprocessor command.  The module
              Ast_mapper(3) implements the external interface of a preprocessor.

       -principal
              Check information path during type-checking, to  make  sure  that  all  types  are  derived  in  a
              principal way.  When using labelled arguments and/or polymorphic methods, this flag is required to
              ensure future versions of the compiler will be able to infer types  correctly,  even  if  internal
              algorithms change.  All programs accepted in -principal mode are also accepted in the default mode
              with equivalent types, but different binary signatures, and this may slow down type checking;  yet
              it is a good idea to use it once before publishing source code.

       -rectypes
              Allow  arbitrary recursive types during type-checking.  By default, only recursive types where the
              recursion goes through an object type are supported. Note that once you have created an  interface
              using this flag, you must use it again for all dependencies.

       -runtime-variant suffix
              Add  suffix  to  the  name  of the runtime library that will be used by the program.  If OCaml was
              configured with option -with-debug-runtime, then the d suffix  is  supported  and  gives  a  debug
              version of the runtime.

       -safe-string
              Enforce the separation between types string and bytes, thereby making strings read-only. This will
              become the default in a future version of OCaml.

       -short-paths
              When a type is visible under several module-paths, use the shortest one when printing  the  type's
              name in inferred interfaces and error and warning messages.

       -strict-sequence
              Force the left-hand part of each sequence to have type unit.

       -thread
              Compile or link multithreaded programs, in combination with the system "threads" library described
              in The OCaml user's manual.

       -unsafe
              Turn bound checking off for array and string accesses  (the  v.(i)ands.[i]  constructs).  Programs
              compiled  with  -unsafe  are  therefore  slightly  faster,  but unsafe: anything can happen if the
              program accesses an array or string outside of its bounds.

       -unsafe-string
              Identify the types string and bytes, thereby making strings  writable.  For  reasons  of  backward
              compatibility,  this  is  the  default  setting  for  the moment, but this will change in a future
              version of OCaml.

       -use-runtime runtime-name
              Generate  a  bytecode  executable  file  that  can  be  executed  on  the  custom  runtime  system
              runtime-name, built earlier with ocamlc -make-runtime runtime-name.

       -v     Print  the version number of the compiler and the location of the standard library directory, then
              exit.

       -verbose
              Print all external commands before they are executed, in particular invocations of the C  compiler
              and linker in -custom mode.  Useful to debug C library problems.

       -vmthread
              Compile or link multithreaded programs, in combination with the VM-level threads library described
              in The OCaml user's manual.

       -vnum or -version
              Print the version number of the compiler in short form (e.g. "3.11.0"), then exit.

       -w warning-list
              Enable, disable, or mark as fatal the warnings specified by the argument warning-list.

              Each warning can be enabled or disabled, and each warning can be fatalor non-fatal.  If a  warning
              is  disabled,  it isn't displayed and doesn't affect compilation in any way (even if it is fatal).
              If a warning is enabled, it is displayed  normally  by  the  compiler  whenever  the  source  code
              triggers  it.   If  it  is  enabled  and  fatal,  the  compiler will also stop with an error after
              displaying it.

              The warning-list argument is a sequence of warning specifiers, with no separators between them.  A
              warning specifier is one of the following:

              +num   Enable warning number num.

              -num   Disable warning number num.

              @num   Enable and mark as fatal warning number num.

              +num1..num2   Enable all warnings between num1 and num2 (inclusive).

              -num1..num2   Disable all warnings between num1 and num2 (inclusive).

              @num1..num2   Enable and mark as fatal all warnings between num1 and num2 (inclusive).

              +letter    Enable  the  set  of  warnings corresponding to letter.  The letter may be uppercase or
              lowercase.

              -letter   Disable the set of warnings corresponding to letter.  The letter  may  be  uppercase  or
              lowercase.

              @letter   Enable and mark as fatal the set of warnings corresponding to letter.  The letter may be
              uppercase or lowercase.

              uppercase-letter   Enable the set of warnings corresponding to uppercase-letter.

              lowercase-letter   Disable the set of warnings corresponding to lowercase-letter.

              The warning numbers are as follows.

              1    Suspicious-looking start-of-comment mark.

              2    Suspicious-looking end-of-comment mark.

              3    Deprecated feature.

              4    Fragile pattern matching: matching that will remain complete even if additional  constructors
              are added to one of the variant types matched.

              5    Partially applied function: expression whose result has function type and is ignored.

              6    Label omitted in function application.

              7    Method overridden without using the "method!" keyword

              8    Partial match: missing cases in pattern-matching.

              9    Missing fields in a record pattern.

              10   Expression on the left-hand side of a sequence that doesn't have type unit (and that is not a
              function, see warning number 5).

              11   Redundant case in a pattern matching (unused match case).

              12   Redundant sub-pattern in a pattern-matching.

              13   Override of an instance variable.

              14   Illegal backslash escape in a string constant.

              15   Private method made public implicitly.

              16   Unerasable optional argument.

              17   Undeclared virtual method.

              18   Non-principal type.

              19   Type without principality.

              20   Unused function argument.

              21   Non-returning statement.

              22   Preprocessor warning.

              23   Useless record with clause.

              24   Bad module name: the source file name is not a valid OCaml module name.

              25   Pattern-matching with all clauses guarded.

              26   Suspicious unused variable: unused variable that is bound with let or as, and  doesn't  start
              with an underscore (_) character.

              27    Innocuous  unused  variable:  unused variable that is not bound with let nor as, and doesn't
              start with an underscore (_) character.

              28   A pattern contains a constant constructor applied to the underscore (_) pattern.

              29   A non-escaped end-of-line was found  in  a  string  constant.   This  may  cause  portability
              problems between Unix and Windows.

              30   Two labels or constructors of the same name are defined in two mutually recursive types.

              31   A module is linked twice in the same executable.

              32   Unused value declaration.

              33   Unused open statement.

              34   Unused type declaration.

              35   Unused for-loop index.

              36   Unused ancestor variable.

              37   Unused constructor.

              38   Unused extension constructor.

              39   Unused rec flag.

              40   Constructor or label name used out of scope.

              41   Ambiguous constructor or label name.

              42   Disambiguated constructor or label name.

              43   Nonoptional label applied as optional.

              44   Open statement shadows an already defined identifier.

              45   Open statement shadows an already defined label or constructor.

              46   Error in environment variable.

              47   Illegal attribute payload.

              48   Implicit elimination of optional arguments.

              49   Missing cmi file when looking up module alias.

              50   Unexpected documentation comment.

              The  letters  stand for the following sets of warnings.  Any letter not mentioned here corresponds
              to the empty set.

              A  all warnings

              C  1, 2

              D  3

              E  4

              F  5

              K  32, 33, 34, 35, 36, 37, 38, 39

              L  6

              M  7

              P  8

              R  9

              S  10

              U  11, 12

              V  13

              X  14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30

              Y  26

              Z  27

              The default setting is -w +a-4-6-7-9-27-29-32..39-41-42-44-45-48-50.  Note that warnings  5 and 10
              are not always triggered, depending on the internals of the type checker.

       -warn-error warning-list
              Mark  as  errors the warnings specified in the argument warning-list.  The compiler will stop with
              an error when one of these warnings is emitted.  The warning-list has the same meaning as for  the
              -w  option:  a + sign (or an uppercase letter) marks the corresponding warnings as fatal, a - sign
              (or a lowercase letter) turns them back into non-fatal warnings, and a @  sign  both  enables  and
              marks as fatal the corresponding warnings.

              Note:  it  is  not  recommended  to use the -warn-error option in production code, because it will
              almost certainly prevent compiling your program with later versions of OCaml  when  they  add  new
              warnings or modify existing warnings.

              The default setting is -warn-error -a (all warnings are non-fatal).

       -warn-help
              Show the description of all available warning numbers.

       -where Print the location of the standard library, then exit.

       - file Process file as a file name, even if it starts with a dash (-) character.

       -help or --help
              Display a short usage summary and exit.

SEE ALSO

       ocamlopt(1), ocamlrun(1), ocaml(1).
       The OCaml user's manual, chapter "Batch compilation".

                                                                                                       OCAMLC(1)