ocamlopt - The Objective Caml native-code compiler
The Objective Caml high-performance
compiles Caml source files to native code object files and link these
object files to produce standalone executables.
command has a command-line interface very close to that
It accepts the same types of arguments and processes them
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
compiler produces a compiled interface
in the file
The interface produced is identical to that
produced by the bytecode compiler
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
compiler produces two files:
containing native object code, and
containing extra information for linking and
optimization of the clients of the unit. The compiled implementation
should always be referred to under the name
(when given a .o file,
assumes that it contains code compiled from C, not from Caml).
The implementation is checked against the interface file
(if it exists) as described in the manual for
Arguments ending in .cmx are taken to be compiled object code. These
files are linked together, along with the object files obtained
by compiling .ml arguments (if any), and the Caml Light standard
library, to produce 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
file must come
before all .cmx files that refer to the unit
Arguments ending in .cmxa are taken to be libraries of object code.
Such a library packs in two files
a set of object files (.cmx/.o files). Libraries are build with
(see the description of the
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
is the same compiler as
but compiled with itself instead of with the bytecode compiler
Thus, it behaves exactly like
but compiles faster.
is not available in all installations of Objective Caml.
The following command-line options are recognized by
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
-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
BR -cclib and -ccopt
options as if they had been provided on the
command line, unless the
option is given.
Dump detailed information about the compilation (types, bindings,
tail-calls, etc). The information for file
is put into file
In case of a type error, dump all the information inferred by the
type-checker before the error. The
file can be used with the emacs commands given in
to display types and other annotations interactively.
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.
as the C linker called to build the final executable and as the C
compiler for compiling .c source files.
option to the linker. This causes the given C library to be linked
with the program.
Pass the given option to the C compiler and linker. For instance,
causes the C linker to search for C libraries in
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.
Print the version number of
and a detailed summary of its configuration, then exit.
Generate an object file (.cmx and .o files) that can later be included
as a sub-module (with the given access path) of a compilation unit
ocamlopt -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.
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
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.
Add the given directory to the list of directories searched for
compiled interface files (.cmi) and compiled object code files
(.cmo). 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,
adds the subdirectory
of the standard library to the search path.
Set aggressiveness of inlining to
is a positive
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,
allows slightly larger functions to be inlined, resulting
in a slight expansion in code size. Higher values for the
option cause larger and larger functions to become candidate for
inlining, but can result in a serious increase in code size.
Compile the file
as an interface file, even if its extension is not .mli.
Recognize file names ending with
as interface files (instead of the default .mli).
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.
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
flag), setting the
flag forces all
subsequent links of programs involving that library to link all the
modules contained in the library.
Do not compile assertion checks. Note that the special form
is always compiled because it is typed specially.
This flag has no effect when linking already-compiled files.
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
and pass the correct C libraries and options on the command line.
Allow the compiler to use some optimizations that are valid only for code
that is never dynlinked.
Ignore non-optional labels in types. Labels cannot be used in
applications, and parameter order becomes strict.
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
option is given, specify the name of the library produced. If the
option is given, specify the name of the packed object file produced.
option is given, specify the name of the output file produced. If the
option is given, specify the name of plugin file produced.
Cause the linker to produce a C object file instead of an executable
file. This is useful to wrap Caml code as a C library,
callable from any C program. The name of the output object file is
camlprog.o by default; it can be set with the
This option can also be used to produce a compiled shared/dynamic
library (.so extension).
Generate extra code to write profile information when the program is
executed. The profile information can then be examined with the
option must be given both at
compile-time and at link-time. Linking object files not compiled with
is possible, but results in less precise profiling.
man page for more information about the profiles.
Full support for
is only available for certain platforms
(currently: Intel x86/Linux and Alpha/Digital Unix).
On other platforms, the
option will result in a less precise
profile (no call graph information, only a time profile).
Build an object file (.cmx and .o files) and its associated compiled
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
option. For instance,
ocamlopt -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 referenced 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
option. In the example above,
A.cmx, B.cmx and C.cmx must have been compiled with
ocamlopt -for-pack P.
Multiple levels of packing can be achieved by combining
The Objective Caml user's manual,
chapter "Native-code compilation" for more details.
Cause the compiler to call the given
as a preprocessor for each source file. The output of
is redirected to
an intermediate file, which is compiled. If there are no compilation
errors, the intermediate file is deleted afterwards.
Check information path during type-checking, to make sure that all
types are derived in a principal way. All programs accepted in
mode are also accepted in default mode with equivalent
types, but different binary signatures.
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.
Keep the assembly code produced during the compilation. The assembly
code for the source file
is saved in the file
Build a plugin (usually .cmxs) that can be dynamically loaded with
module. The name of the plugin must be
set with the
option. A plugin can include a number of Caml
modules and libraries, and extra native objects (.o, .a files).
Building native plugins is only supported for some
operating system. Under some systems (currently,
only Linux AMD 64), all the Caml code linked in a plugin must have
been compiled without the
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).
Compile or link multithreaded programs, in combination with the
system threads library described in
The Objective Caml user's manual.
Turn bound checking off for array and string accesses (the
constructs). Programs compiled with
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 modulus operations.
an integer division (or modulus) by zero can halt the
program or continue with an unspecified result instead of raising a
Print the version number of the compiler and the location of the
standard library directory, then exit.
Print all external commands before they are executed, in particular
invocations of the assembler, C compiler, and linker.
Print the version number of the compiler in short form (e.g. "3.11.0"),
Enable or disable warnings according to the argument
The argument is a set of letters. If a letter is
uppercase, it enables the corresponding warnings; lowercase disables
the warnings. The correspondence is the following:
start of comments that look like mistakes
use of deprecated features
fragile pattern matchings (matchings that will remain
complete even if additional constructors are added to one of the
variant types matched)
partially applied functions (expressions whose result has
function type and is ignored)
omission of labels in applications
overriding of methods
missing cases in pattern matchings (i.e. partial matchings)
expressions in the left-hand side of a sequence that don't
(and that are not functions, see
redundant cases in pattern matching (unused cases)
overriding of instance variables
unused variables that are bound with
let or as,
and don't start with an underscore (_) character
all other cases of unused variables that don't start with an
underscore (_) character
warnings that don't fit in the above categories (except
The default setting is
enabling all warnings except fragile
pattern matchings, omitted labels, and innocuous unused variables.
Note that warnings
F and S
are not always triggered, depending on the internals of the type checker.
Turn the warnings indicated in the argument
into errors. The compiler will stop with an error when one of these
warnings is emitted. The
has the same meaning as for
the "-w" option: an uppercase character turns the corresponding
warning into an error, a lowercase character leaves it as a warning.
The default setting is
(none of the warnings is treated as an error).
Print the location of the standard library, then exit.
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
following additional option:
Use the IA32 instructions to compute
trigonometric and exponential functions, instead of calling the
corresponding library routines. The functions affected are:
The resulting code runs faster, but the range of supported arguments
and the precision of the result can be reduced. In particular,
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:
Generate position-independent machine code. This is the default.
Generate position-dependent machine code.
OPTIONS FOR THE SPARC ARCHITECTURE
The Sparc code generator supports the following additional options:
Generate SPARC version 8 code.
Generate SPARC version 9 code.
The default is to generate code for SPARC version 7, which runs on all
The Objective Caml user's manual,
chapter "Native-code compilation".