ic

The Erlang IDL Compiler

The ic module is an Erlang implementation of an OMG IDL compiler. Depending on the choice of back-end the code will map to Erlang, C, or Java. The compiler generates client stubs and server skeletons.

Two kinds of files are generated for each scope: Ordinary code files and header files. The latter are used for defining record definitions, while the ordinary files contain the object interface functions.

Functions

ic:gen(FileName) -> Result

ic:gen(FileName, [Option]) -> Result

Result = ok | error | {ok, [Warning]} | {error, [Warning], [Error]}
Option = [ GeneralOption | CodeOption | WarningOption | BackendOption]
GeneralOption =
{outdir, String()} | {cfgfile, String()} | {use_preproc, bool()} |
{preproc_cmd, String()} | {preproc_flags, String()}
CodeOption =
{gen_hrl, bool()} | {serv_last_call, exception | exit} | {{impl, String()}, String()} | {light_ifr, bool()}
this | {this, String()} | {{this, String()}, bool()} |
from | {from, String()} | {{from, String()}, bool()} |
handle_info | {handle_info, String()} | {{handle_info, String()}, bool()} |
timeout | {timeout, String()} | {{timeout, String()}, bool()} |
{scoped_op_calls, bool()} | {scl, bool()} |
{user_protocol, Prefix} |
{c_timeout, {SendTimeout, RecvTimeout}} |
{c_report, bool()} |
{precond, {atom(), atom()}} | {{precond, String()} {atom(), atom()}} |
{postcond, {atom(), atom()}} | {{postcond, String()} {atom(), atom()}}
WarningOption =
{'Wall', bool()} | {maxerrs, int() | infinity} |
{maxwarns, int() | infinity} | {nowarn, bool()} |
{warn_name_shadow, bool()} | {pedantic, bool()} |
{silent, bool()}
BackendOption = {be, Backend}
Backend = erl_corba | erl_template | erl_plain | erl_genserv | c_client | c_server | java
DirNAme = string() | atom()
FileName = string() | atom()

The tuple {Option, true} can be replaced by Option for boolean values.

The ic:gen/2 function can be called from the command line as follows:

erlc "+Option" ... File.idl

Example:

erlc "+{be,c_client}" '+{outdir, "../out"}' File.idl

General options

outdir

Places all output files in the directory given by the option. The directory will be created if it does not already exist.

Example option: {outdir, "output/generated"}.

cfgfile

Uses FileName as configuration file. Options will override compiler defaults but can be overridden by command line options. Default value is ".ic_config".

Example option: {cfgfile, "special.cfg"}.

use_preproc

Uses a preprocessor. Default value is true.

preproc_cmd

Command string to invoke the preprocessor. The actual command will be built as preproc_cmd++preproc_flags++FileName

Example option: {preproc_cmd, "erl"}).

Example option: {preproc_cmd, "gcc -x c++ -E"}.

preproc_flags

Flags given to the preprocessor.

Example option: {preproc_flags, "-I../include"}.

Code options

light_ifr

Currently, the default setting is false. To be able to use this option Orber must be configured to use Light IFR (see Orber's User's Guide). When this options is used, the size of the generated files used to register the API in the IFR DB are minimized.

Example option: {light_ifr, true}.

gen_hrl

Generate header files. Default is true.

serv_last_call

Makes the last gen_server handle_call either raise a CORBA exception or just exit plainly. Default is the exception.

{{impl, IntfName}, ModName}

Assumes that the interface with name IntfName is implemented by the module with name ModName and will generate calls to the ModName module in the server behavior. Note that the IntfName must be a fully scoped name as in "M1::I1".

this

Adds the object reference as the first parameter to the object implementation functions. This makes the implementation aware of its own object reference.
The option comes in three varieties: this which activates the parameter for all interfaces in the source file, {this, IntfName} which activates the parameter for a specified interface and {{this, IntfName}, false} which deactivates the parameter for a specified interface.

Example option: this) activates the parameter for all interfaces.

Example option: {this, "M1::I1"} activates the parameter for all functions of M1::I1.

Example options: [this, {{this, "M1::I2"}, false}] activates the parameter for all interfaces except M1::I2.

from

Adds the invokers reference as the first parameter to the object implementation two-way functions. If both from and this options are used the invokers reference parameter will be passed as the second parameter. This makes it possible for the implementation to respond to a request and continue executing afterwards. Consult the gen_server and Orber documentation how this option may be used.
The option comes in three varieties: from which activates the parameter for all interfaces in the source file, {from, IntfName} which activates the parameter for a specified interface and {{from, IntfName}, false} which deactivates the parameter for a specified interface.

Example option: from) activates the parameter for all interfaces.

Example options: [{from, "M1::I1"}] activates the parameter for all functions of M1::I1.

Example options: [from, {{from, "M1::I2"}, false}] activates the parameter for all interfaces except M1::I2.

handle_info

Makes the object server call a function handle_info in the object implementation module on all unexpected messages. Useful if the object implementation need to trap exits.

Example option: handle_info will activates module implementation handle_info for all interfaces in the source file.

Example option: {{handle_info, "M1::I1"}, true} will activates module implementation handle_info for the specified interface.

Example options: [handle_info, {{handle_info, "M1::I1"}, false}] will generate the handle_info call for all interfaces except M1::I1.

timeout

Used to allow a server response time limit to be set by the user. This should be a string that represents the scope for the interface which should have an extra variable for wait time initialization.

Example option: {timeout,"M::I"}) produces server stub which will has an extra timeout parameter in the initialization function for that interface.

Example option: timeout produces server stub which will has an extra timeout parameter in the initialization function for all interfaces in the source file.

Example options: [timeout, {{timeout,"M::I"}, false}] produces server stub which will has an extra timeout parameter in the initialization function for all interfaces except M1::I1.

scoped_op_calls

Used to produce more refined request calls to server. When this option is set to true, the operation name which was mentioned in the call is scoped. This is essential to avoid name clashes when communicating with c-servers. This option is available for the c-client, c-server and the Erlang gen_server back ends. All of the parts generated by ic have to agree in the use of this option. Default is false.

Example options: [{be,c_genserv},{scoped_op_calls,true}]) produces client stubs which sends "scoped" requests to a gen_server or a c-server.

user_protocol

Used to define a own protocol different from the default Erlang distribution + gen_server protocol. Currently only valid for C back-ends. For further details see IC C protocol.

Example options: [{be,c_client},{user_protocol, "my_special"}]) produces client stubs which use C protocol functions with the prefix "my_special".

c_timeout

Makes sends and receives to have timeouts (C back-ends only). These timeouts are specified in milliseconds.

Example options: [{be,c_client},{c_timeout, {10000, 20000}}]) produces client stubs which use a 10 seconds send timeout, and a 20 seconds receive timeout.

c_report

Generates code for writing encode/decode errors to stderr (C back-ends only). timeouts are specified in milliseconds.

Example options: [{be,c_client}, c_report]).

scl

Used for compatibility with previous compiler versions up to 3.3. Due to better semantic checks on enumerants, the compiler discovers name clashes between user defined types and enumerant values in the same name space. By enabling this option the compiler turns off the extended semantic check on enumerant values. Default is false.

Example option: {scl,true}

precond

Adds a precondition call before the call to the operation implementation on the server side.

The option comes in three varieties: {precond, {M, F}} which activates the call for operations in all interfaces in the source file, {{precond, IntfName}, {M, F}} which activates the call for all operations in a specific interface and {{precond, OpName}, {M, F}} which activates the call for a specific operation.

The precondition function has the following signature m:f(Module, Function, Args).

Example option: {precond, {mod, fun}} adds the call of m:f for all operations in the idl file.

Example options: [{{precond, "M1::I"}, {mod, fun}}] adds the call of m:f for all operations in the interface M1::I1.

Example options: [{{precond, "M1::I::Op"}, {mod, fun}}] adds the call of m:f for the operation M1::I::Op.

postcond

Adds a postcondition call after the call to the operation implementation on the server side.

The option comes in three varieties: {postcond, {M, F}} which activates the call for operations in all interfaces in the source file, {{postcond, IntfName}, {M, F}} which activates the call for all operations in a specific interface and {{postcond, OpName}, {M, F}} which activates the call for a specific operation.

The postcondition function has the following signature m:f(Module, Function, Args, Result).

Example option: {postcond, {mod, fun}} adds the call of m:f for all operations in the idl file.

Example options: [{{postcond, "M1::I"}, {mod, fun}}] adds the call of m:f for all operations in the interface M1::I1.

Example options: [{{postcond, "M1::I::Op"}, {mod, fun}}] adds the call of m:f for the operation M1::I::Op.

Warning options

'Wall'

The option activates all reasonable warning messages in analogy with the gcc -Wall option. Default value is true.

maxerrs

The maximum numbers of errors that can be detected before the compiler gives up. The option can either have an integer value or the atom infinity. Default number is 10.

maxwarns

The maximum numbers of warnings that can be detected before the compiler gives up. The option can either have an integer value or the atom infinity. Default value is infinity.

nowarn

Suppresses all warnings. Default value is false.

warn_name_shadow

Warning appears whenever names are shadowed due to inheritance; for example, if a type name is redefined from a base interface. Note that it is illegal to overload operation and attribute names as this causes an error to be produced. Default value is true.

pedantic

Activates all warning options. Default value is false.

silent

Suppresses compiler printed output. Default value is false.

Back-End options

Which back-end IC will generate code for is determined by the supplied {be,atom()} option. If left out, erl_corba is used. Currently, IC support the following back-ends:

erl_corba

This option switches to the IDL generation for CORBA.

erl_template

Generate CORBA call-back module templates for each interface in the target IDL file. Note, will overwrite existing files.

erl_plain

Will produce plain Erlang modules which contain functions that map to the corresponding interface functions on the input file.

erl_genserv

This is an IDL to Erlang generic server generation option.

c_client

Will produce a C client to the generic Erlang server.

c_server

Will produce a C server switch with functionality of a generic Erlang server.

java

Will produce Java client stubs and server skeletons with functionality of a generic Erlang server.

c_genserv

Deprecated. Use c_client instead.

Preprocessor

The IDL compiler allows several preprocessors to be used, the Erlang IDL preprocessor or other standard C preprocessors. Options can be used to provide extra flags such as include directories to the preprocessor. The build in the Erlang IDL preprocessor is used by default, but any standard C preprocessor such as gcc is adequate.

The preprocessor command is formed by appending the prepoc_cmd to the preproc_flags option and then appending the input IDL file name.

Configuration

The compiler can be configured in two ways:

Configuration file

Command line options

The configuration file is optional and overrides the compiler defaults and is in turn overridden by the command line options. The configuration file shall contain options in the form of Erlang terms. The configuration file is read using file:consult.

An example of a configuration file, note the "." after each line.

{outdir, gen_dir}.
{{impl, "M1::M2::object"}, "obj"}.

Output files

The compiler will produce output in several files depending on scope declarations found in the IDL file. At most three file types will be generated for each scope (including the top scope), depending on the compiler back-end and the compiled interface. Generally, the output per interface will be a header file (.hrl/ .h) and one or more Erlang/C files (.erl/.c). Please look at the language mapping for each back-end for details.

There will be at least one set of files for an IDL file, for the file level scope. Modules and interfaces also have their own set of generated files.