GCC* Compatibility and Interoperability

This topic applies to Linux*.

The Intel® C++ Compiler is compatible with most versions of the GNU Compiler Collection (GCC*). The release notes contains a list of compatible versions.

C language object files created with the Intel® C++ Compiler are binary compatible with GCC* and C/C++ language library. You can use the Intel® C++ Compiler or the GCC compiler to pass object files to the linker.

Note

When using an Intel software development product that includes an Intel® C++ Compiler with a Clang front-end, you can also use icc -qnextgen or icpc -qnextgen.

The Intel® C++ Compiler supports many of the language extensions provided by the GNU compilers. See http://www.gnu.org for more information.

Note

Statement expressions are supported, except that the following are prohibited inside them:

  • dynamically-initialized local static variables

  • local non-POD class definitions

  • try/catch

  • variable length arrays

Branching out of a statement expression and statement expressions in constructor initializers are not allowed. Variable-length arrays are no longer allowed in statement expressions.

Note

The Intel® C++ Compiler supports GCC-style inline ASM if the assembler code uses AT&T* System V/386 syntax.

GCC Interoperability

C++ compilers are interoperable if they can link object files and libraries generated by one compiler with object files and libraries generated by the second compiler, and the resulting executable runs successfully. The Intel® C++ Compiler is highly compatible with the GNU compilers.

The Intel® C++ Compiler and GNU GCC* compiler support the following predefined macros:

  • __GNUC__

  • __GNUG__

  • __GNUC_MINOR__

  • __GNUC_PATCHLEVEL__

You can specify the -no-gcc option to undefine these macros. If you need GCC* interoperability (-cxxlib), do not use the -no-gcc compiler option.

CAUTION

Not defining these macros results in different paths through system header files. These alternate paths may be poorly tested or otherwise incompatible.

How the Compiler Uses GCC

The Intel® C++ Compiler uses the GNU* tools on the system, such as the GNU header files, including stdio.h, and the GNU linker and libraries. So the compiler has to be compatible with the version of GCC or g++ you have on your system.

By default, the compiler determines which version of GCC or g++ you have installed from the PATH environment variable.

If you want use a version of GCC or g++ other than the default version on your system, you need to use either the -gcc-name or -gxx-name compiler option to specify the path to the version of GCC or g++ that you want to use. For example:

  • You want to build something that cannot be compiled by the default version of the system compiler, so you need to use a legacy version for compatibility, such as if you want to use third party libraries that are not compatible with the default version of the system compiler.

  • You want to use a later version of GCC or g++ than the default system compiler.

The Intel compiler driver uses the default version of GCC/g++, or the version you specify, to extract the location of the headers and libraries.

The cxxlib options are connected to linking in the GNU C++ library. These options are not directly related to -gcc-name or -gxx-name.

  • -cxxlib-nostd prevents the compiler from searching the C++ system include directories for the C++ standard library libstdc++. For example: If you specify -cxxlib-nostd, then #include <iostream> does not compile but #include <stdio.h> does. This option also prevents linking of libstdc++, because the driver leaves off the -lstdc++ option.

  • -no-cxxlib affects the linking of all C++ runtime libraries, not just libstdc++. So a program that only uses printf, for example, does not link if you specify -no-cxxlib, but it does link if you specify -cxxlib-nostd.

  • -cxxlib=dir modifies the top level location for binaries and libraries. For example, if you specify icc -gxx-name=/my/directory/g++ -cxxlib=/cxxlib/dir, the driver attempts to find g++ in /cxxlib/dir/my/directory

Compatibility with Open Source Tools

The Intel® C++ Compiler includes improved support for the following open source tools:

  • GNU Libtool – a script that allows package developers to provide generic shared library support.

  • Valgrind – a flexible system for debugging and profiling executables running on x86 processors.

  • GNU Automake – a tool for automatically generating Makefile.ins from files called Makefile.am.

Para obtener información más completa sobre las optimizaciones del compilador, consulte nuestro Aviso de optimización.