The erlc program provides a common way to run all compilers
in the Erlang system. Depending on the extension of each input file,
erlc invokes the appropriate compiler. Regardless of which compiler
is used, the same flags are used to provide parameters, such as include
paths and output directory.
The current working directory, ".", is not
included in the code path when running the compiler. This is to avoid
loading Beam files from the current working directory that could potentially
be in conflict with the compiler or the Erlang/OTP system used by the
compiler.
Compiles one or more files. The files must include the extension,
for example, .erl for Erlang source code, or .yrl for Yecc
source code. Erlc uses the extension to invoke the correct
compiler.
The following flags are supported:
-I <Directory>
Instructs the compiler to search for include files in the
Directory. When encountering an
-include or
-include_lib
directive, the compiler searches for header files in the following
directories:
•".", the current working
directory of the file server
•The base name of the compiled file
•The directories specified using option -I;
the directory specified last is searched first
-o <Directory>
The directory where the compiler is to place the output
files. Defaults to the current working directory.
-D<Name>
Defines a macro.
-D<Name>=<Value>
Defines a macro with the specified value. The value can
be any Erlang term. Depending on the platform, the value may need to be quoted
if the shell itself interprets certain characters. On Unix, terms containing
tuples and lists must be quoted. Terms containing spaces must be quoted on all
platforms.
-WError
Makes all warnings into errors.
-W<Number>
Sets warning level to Number. Defaults to
1. To turn off warnings, use -W0.
-W
Same as -W1. Default.
-v
Enables verbose output.
-b <Output_type>
Specifies the type of output file. Output_type is
the same as the file extension of the output file, but without the period.
This option is ignored by compilers that have a single output format.
-no-server
Do not use the compile server.
-server
Use the compile server.
-enable-feature <Feature>
Enables the feature feature during compilation.
The special feature all can be used to enable all features.
-disable-feature <feature>
Disables the feature feature during compilation.
The special feature all can be used to disable all non permanent
features.
-list-features
List short descriptions of the current configurable
features. Non-configurable features (those with status rejected or
permanent) will not be shown.
-describe-feature <feature>
Show long description and history of feature
feature.
-M
Produces a Makefile rule to track header dependencies.
The rule is sent to stdout. No object file is produced.
-MMD
Generate dependencies as a side-effect. The object file
will be produced as normal. This option overrides the option -M.
-MF <Makefile>
As option -M, except that the Makefile is written
to Makefile. No object file is produced.
-MD
Same as -M -MF <File>.Pbeam.
-MT <Target>
In conjunction with option -M or -MF,
changes the name of the rule emitted to Target.
-MQ <Target>
As option -MT, except that characters special to
make/1 are quoted.
-MP
In conjunction with option -M or -MF, adds
a phony target for each dependency.
-MG
In conjunction with option -M or -MF,
considers missing headers as generated files and adds them to the
dependencies.
--
Signals that no more options will follow. The rest of the
arguments is treated as filenames, even if they start with hyphens.
+<Term>
A flag starting with a plus (
+) rather than a
hyphen is converted to an Erlang term and passed unchanged to the compiler.
For example, option
export_all for the Erlang compiler can be specified
as follows:
-
erlc +export_all file.erl
Depending on the platform, the value may need to be quoted if the
shell itself interprets certain characters. On Unix, terms containing tuples
and lists must be quoted. Terms containing spaces must be quoted on all
platforms.
The following flags are useful in special situations, such as
rebuilding the OTP system:
-pa <Directory>
Appends Directory to the front of the code path in
the invoked Erlang emulator. This can be used to invoke another compiler than
the default one.
-pz <Directory>
Appends Directory to the code path in the invoked
Erlang emulator.
The following compilers are supported:
.erl
Erlang source code. It generates a
.beam file.
Options -P, -E, and -S are equivalent to
+'P', +'E', and +'S', except that it is not necessary
to include the single quotes to protect them from the shell.
Supported options: -I, -o, -D, -v,
-W, -b.
.S
Erlang assembler source code. It generates a
.beam
file.
Supported options: same as for .erl.
.core
Erlang core source code. It generates a
.beam
file.
Supported options: same as for .erl.
.yrl
Yecc source code. It generates an
.erl file.
Use option -I with the name of a file to use that file as a
customized prologue file (option includefile).
Supported options: -o, -v, -I, -W.
.mib
MIB for SNMP. It generates a
.bin file.
Supported options: -I, -o, -W.
.bin
A compiled MIB for SNMP. It generates a
.hrl file.
Supported options: -o, -v.
.rel
Script file. It generates a boot file.
Use option -I to name directories to be searched for
application files (equivalent to the path in the option list for
systools:make_script/2).
Supported option: -o.
.asn1
ASN1 file. It creates an
.erl,
.hrl, and
.asn1db file from an
.asn1 file. Also compiles the
.erl
using the Erlang compiler unless option
+noobj is specified.
Supported options: -I, -o, -b, -W.
.idl
IC file. It runs the IDL compiler.
Supported options: -I, -o.
The compile server can be used to potentially speed up the build
of multi-file projects by avoiding to start an Erlang system for each file
to compile. Whether it will speed up the build depends on the nature of the
project and the build machine.
By default, the compile server is not used. It can be enabled by
giving erlc the option -server or by setting the environment
variable ERLC_USE_SERVER to yes or true.
When the compile server is enabled, erlc will automatically
use the server if it is started and start the server if has not already
started. The server will terminate itself when it has been idle for some
number of seconds.
erlc and the compile server communicate using the Erlang
distribution. The compile server is started as a hidden node, with a name
that includes the current user. Thus, each user on a computer has their own
compile server.
Using the compile server does not always speed up the build, as
the compile server sometimes must be restarted to ensure correctness. Here
are some examples of situations that force a restart:
•erlc wants to use a different version of
Erlang than the compile server is using.
•erlc wants to use different options for
erl than the compile server was started with. (A change to code path
using the option -pa could cause different parse transforms to be
loaded. To be safe, the compile server will be restarted when any erl
option is changed.)
•If the current working directory for erlc
is different from the working directory active when the compile server was
started, and if the compile server has active jobs, it will be
restarted as soon as those jobs have finished. (Build systems that build files
randomly across multiple directories in parallel will probably not benefit
from the compile server.)
ERLC_EMULATOR
The command for starting the emulator. Defaults to
erl in the same directory as the erlc program itself, or, if it
does not exist, erl in any of the directories specified in environment
variable PATH.
ERLC_USE_SERVER
Allowed values are yes or true to use the
compile server, and no or false to not use the compile server.
If other values are given, erlc will print a warning message and
continue.
ERLC_SERVER_ID
Tells erlc to identify the compile server by the
given name, allowing a single user to run multiple unrelated builds in
parallel without them affecting each other, which can be useful for shared
build machines and the like. The name must be alphanumeric, and it
defaults to being empty.