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.
- -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 -l xxx.
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.
If the given directory starts with +, it is taken relative to the
standard library directory. For instance, -I +labltk adds
the subdirectory labltk 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).
- -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-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 include the standard library directory in the list of directories
searched for compiled interfaces (see 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.
- -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 format of the input and output of the preprocessor are
not yet documented.
- -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.
- -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.
- -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 Camlp4 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 exception 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.
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. 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.
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".