OCAMLOPT(1)OCAMLOPT(1)NAME
ocamlopt - The OCaml native-code compiler
SYNOPSIS
ocamlopt [ options ] filename ...
ocamlopt.opt (same options)
DESCRIPTION
The OCaml high-performance native-code compiler ocamlopt(1) compiles
OCaml source files to native code object files and link these object
files to produce standalone executables.
The ocamlopt(1) command has a command-line interface very close to that
of ocamlc(1). It accepts the same 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
ocamlopt(1) compiler produces a compiled interface in the file x.cmi.
The interface produced is identical to that produced by the bytecode
compiler ocamlc(1).
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 ocamlopt(1) compiler pro‐
duces two files: x.o, containing native object code, and x.cmx, con‐
taining extra information for linking and optimization of the clients
of the unit. The compiled implementation should always be referred to
under the name x.cmx (when given a .o file, ocamlopt(1) assumes that it
contains code compiled from C, not from OCaml).
The implementation is checked against the interface file x.mli (if it
exists) as described in the manual for ocamlc(1).
Arguments ending in .cmx are taken to be compiled object code. These
files are linked together, along with the object files obtained by com‐
piling .ml arguments (if any), and the OCaml standard library, to pro‐
duce a native-code executable program. The order in which .cmx 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.cmx file must come before all .cmx files that refer to the
unit x.
Arguments ending in .cmxa are taken to be libraries of object code.
Such a library packs in two files lib.cmxa and lib.a a set of object
files (.cmx/.o files). Libraries are build with ocamlopt -a (see the
description of the -a option below). The object files contained in the
library are linked as regular .cmx files (see above), in the order
specified when the library 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.
Arguments ending in .o or .a are assumed to be C object files and
libraries. They are linked with the program.
The output of the linking phase is a regular Unix executable file. It
does not need ocamlrun(1) to run.
ocamlopt.opt is the same compiler as ocamlopt, but compiled with itself
instead of with the bytecode compiler ocamlc(1). Thus, it behaves
exactly like ocamlopt, but compiles faster. ocamlopt.opt is not avail‐
able in all installations of OCaml.
OPTIONS
The following command-line options are recognized by ocamlopt(1).
-a Build a library (.cmxa/.a file) with the object files (.cmx/.o
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 -cclib or -ccopt options are passed on the command line,
these options are stored in the resulting .cmxa library. Then,
linking with this library automatically adds back the
-cclib and -ccopt options as if they had been provided on the
command line, unless the -noautolink option is given. Addition‐
ally, 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, bind‐
ings, 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, bind‐
ings, 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 exe‐
cutable file is produced. This option is useful to compile mod‐
ules separately.
-cc ccomp
Use ccomp as the C linker called to build the final executable
and as the C compiler for compiling .c source files.
-cclib -llibname
Pass the -llibname option to the linker. This causes the given C
library to be linked with the program.
-ccopt option
Pass the given option to the C compiler and linker. For
instance, -ccopt -Ldir causes the C linker to search for C
libraries in directory dir.
-compact
Optimize the produced code for space rather than for time. This
results in smaller but slightly slower programs. The default is
to optimize for speed.
-config
Print the version number of ocamlopt(1) and a detailed summary
of its configuration, then exit.
-for-pack module-path
Generate an object file (.cmx and .o files) that can later be
included as a sub-module (with the given access path) of a com‐
pilation unit constructed with -pack. For instance, ocam‐
lopt -for-pack P -c A.ml will generate a.cmx and a.o files that
can later be used with ocamlopt -pack -o P.cmx a.cmx.
-g Add debugging information while compiling and linking. This
option is required in order to produce stack backtraces when the
program terminates on an uncaught exception (see ocamlrun(1)).
-i Cause the compiler to print all defined names (with their
inferred types or their definitions) when compiling an implemen‐
tation (.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 inter‐
faces, 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
(.cmx), and libraries (.cmxa). By default, the current directory
is searched first, then the standard library directory. Directo‐
ries 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 -nost‐
dlib.
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.
-inline n
Set aggressiveness of inlining to n, where n is a positive inte‐
ger. Specifying -inline 0 prevents all functions from being
inlined, except those whose body is smaller than the call site.
Thus, inlining causes no expansion in code size. The default
aggressiveness, -inline 1, allows slightly larger functions to
be inlined, resulting in a slight expansion in code size. Higher
values for the -inline option cause larger and larger functions
to become candidate for inlining, but can result in a serious
increase in code size.
-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-locs
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 applica‐
tions, 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 (-a flag), setting the -linkall flag
forces all subsequent links of programs involving that library
to link all the modules contained in the library.
-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 .cmxa libraries, ignore -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.
-nodynlink
Allow the compiler to use some optimizations that are valid only
for code that is never dynlinked.
-nostdlib
Do not automatically add the standard library directory the list
of directories searched for compiled interface files (.cmi),
compiled object code files (.cmx), and libraries (.cmxa). See
also option -I.
-nolabels
Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
-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 tradi‐
tion. 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. If the
-shared option is given, specify the name of plugin file pro‐
duced. 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 imple‐
mentation 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 an exe‐
cutable 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 compiled shared/dynamic library (.so extension).
-p Generate extra code to write profile information when the pro‐
gram is executed. The profile information can then be examined
with the analysis program gprof(1). The -p option must be given
both at compile-time and at link-time. Linking object files not
compiled with -p is possible, but results in less precise pro‐
filing.
See the gprof(1) man page for more information about the pro‐
files.
Full support for gprof(1) is only available for certain plat‐
forms (currently: Intel x86/Linux and Alpha/Digital Unix). On
other platforms, the -p option will result in a less precise
profile (no call graph information, only a time profile).
-pack Build an object file (.cmx and .o files) and its associated com‐
piled interface (.cmi) that combines the .cmx object files given
on the command line, making them appear as sub-modules of the
output .cmx file. The name of the output .cmx file must be
given with the -o option. For instance, ocam‐
lopt -pack -o P.cmx A.cmx B.cmx C.cmx generates compiled files
P.cmx, P.o and P.cmi describing a compilation unit having three
sub-modules A, B and C, corresponding to the contents of the
object files A.cmx, B.cmx and C.cmx. These contents can be ref‐
erenced as P.A, P.B and P.C in the remainder of the program.
The .cmx object files being combined must have been compiled
with the appropriate -for-pack option. In the example above,
A.cmx, B.cmx and C.cmx must have been compiled with ocam‐
lopt -for-pack P.
Multiple levels of packing can be achieved by combining -pack
with -for-pack. See The OCaml user's manual, chapter "Native-
code compilation" for more details.
-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 compila‐
tion errors, the intermediate file is deleted afterwards.
-ppx command
After parsing, pipe the abstract syntax tree through the pre‐
processor 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. All programs accepted
in -principal mode are also accepted in default mode with equiv‐
alent types, but different binary signatures.
-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 depen‐
dencies.
-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.
-S Keep the assembly code produced during the compilation. The
assembly code for the source file x.ml is saved in the file x.s.
-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.
-shared
Build a plugin (usually .cmxs) that can be dynamically loaded
with the Dynlink module. The name of the plugin must be set with
the -o option. A plugin can include a number of OCaml modules
and libraries, and extra native objects (.o, .a files). Build‐
ing native plugins is only supported for some operating system.
Under some systems (currently, only Linux AMD 64), all the OCaml
code linked in a plugin must have been compiled without the
-nodynlink flag. Some constraints might also apply to the way
the extra native objects have been compiled (under Linux AMD 64,
they must contain only position-independent code).
-short-paths
When a type is visible under several module-paths, use the
shortest one when printing the type's name in inferred inter‐
faces and error and warning messages.
-strict-sequence
The left-hand part of a sequence must 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 faster, but unsafe: anything can happen if the program
accesses an array or string outside of its bounds. Additionally,
turn off the check for zero divisor in integer division and mod‐
ulus operations. With -unsafe, an integer division (or modulus)
by zero can halt the program or continue with an unspecified
result instead of raising a Division_by_zero exception.
-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.
-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 partic‐
ular invocations of the assembler, C compiler, and linker.
-version or -vnum
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. See ocamlc(1) for the syntax of warning-
list.
-warn-error warning-list
Mark as fatal the warnings specified in the argument warn‐
ing-list. The compiler will stop with an error when one of
these warnings is emitted. The warning-list has the same mean‐
ing as for the -w option: a + sign (or an uppercase letter)
marks the corresponding warnings as fatal, a - sign (or a lower‐
case 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 com‐
piling 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.
OPTIONS FOR THE IA32 ARCHITECTURE
The IA32 code generator (Intel Pentium, AMD Athlon) supports the fol‐
lowing additional option:
-ffast-math
Use the IA32 instructions to compute trigonometric and exponen‐
tial functions, instead of calling the corresponding library
routines. The functions affected are: atan, atan2, cos, log,
log10, sin, sqrt and tan. The resulting code runs faster, but
the range of supported arguments and the precision of the result
can be reduced. In particular, trigonometric operations cos,
sin, tan have their range reduced to [-2^64, 2^64].
OPTIONS FOR THE AMD64 ARCHITECTURE
The AMD64 code generator (64-bit versions of Intel Pentium and AMD
Athlon) supports the following additional options:
-fPIC Generate position-independent machine code. This is the
default.
-fno-PIC
Generate position-dependent machine code.
OPTIONS FOR THE SPARC ARCHITECTURE
The Sparc code generator supports the following additional options:
-march=v8
Generate SPARC version 8 code.
-march=v9
Generate SPARC version 9 code.
The default is to generate code for SPARC version 7, which runs on all
SPARC processors.
OPTIONS FOR THE ARM ARCHITECTURE
The ARM code generator supports the following additional options:
-farch=armv4|armv5|armv5te|armv6|armv6t2|armv7
Select the ARM target architecture
-ffpu=soft|vfpv2|vfpv3-d16|vfpv3
Select the floating-point hardware
-fPIC Generate position-independent machine code.
-fno-PIC
Generate position-dependent machine code. This is the default.
-fthumb
Enable Thumb/Thumb-2 code generation
-fno-thumb
Disable Thumb/Thumb-2 code generation
The default values for target architecture, floating-point hardware and
thumb usage were selected at configure-time when building ocamlopt
itself. This configuration can be inspected using ocamlopt -config.
Target architecture depends on the "model" setting, while floating-
point hardware and thumb support are determined from the ABI setting in
"system" ( linux_eabiorlinux_eabihf).
SEE ALSOocamlc(1).
The OCaml user's manual, chapter "Native-code compilation".
OCAMLOPT(1)
