Building OCCT using MinGW

Open CASCADE Technology 7.0.0.rc can be built using MinGW-w64 on Windows platform.

MinGW is a minimalistic development environment for developing native Windows applications based on GCC. Project MinGW-w64 is its fork aimed to support 64-bit target and new APIs.

GCC (GNU Compiler Collection) remains a main compiler on Linux platform, but is a second-class citizen on platforms like Windows (with dominating msvc - a C/C++ compiler from Microsoft Visual Studio) or OS X (where Apple has pushed developers towards clang).

GCC provides a strong C/C++ compiler supporting C/C++ features from the most recent standards (including C99 standard abandoned by Microsoft in msvc) and efficient optimizations. Although quite rarely used on Windows, GCC might be still reasonable choice for developers within particular scenarios. OCCT relies on msvc as a main compiler on Windows platform. However, since OCCT 7.0.0 (see related issue on bugtracker #0027197) it is now also possible to use GCC (MinGW-w64) for building. It should be noted, however, that MinGW builds are not yet officially maintained by Open CASCADE team (no regression testing etc.). It is also important to note that GCC uses different mechanisms for implementing C++ features, which are completely incompatible with msvc. Thus DLLs built using MinGW can be used only within application using MinGW as well. Moreover, GCC uses different format for debugging symbols, which is not supported by Visual Studio compiler - GDB should be used instead.

Building OCCT using MinGW

Two ways can be considered to build OCCT using MinGW - CMake and Code::Blocks project files generator (tcl-based genproj.bat tool packaged with OCCT). CMake supports Code::Blocks project files as well ("CodeBlocks - MinGW Makefiles"), but in contrast to genproj.bat, CMake generates these project files without keeping OCCT projects structure and relies on Makefiles rather than built-in Code::Blocks compiler plugins. Cross-compiling should be also possible (one of the benefits of MinGW), but is not considered/tested within this article. As a prerequisite for building OCCT, its dependencies should be built. It is recommended to use Msys2 project for this task, which dramatically simplifies building libraries like Tcl/Tk by providing shell and usual Unix tools. The building of OCCT itself relies on MinGW only and does not depend on msys2.

Configuring MinGW within CMake

For building using CMake, just follow the general guideline. At the very first step you should specify one of the generator option supporting MinGW - e.g. "MinWG Makefiles". CMake will automatically find MinGW tools from current %PATH%, so if you have not configured it system-wide, you can launch cmake-gui within mingwvars.bat environment (the script provided within MinGW installation path). After generation, just go to the folder with generated Makefiles and use mingw32-make.exe as usual make tool in Unix environment.

Generating Code::Blocks projects using genproj.bat

For using genproj.bat (as alternative to CMake), follow the general guideline for using genproj (configure dependencies using genconf.bat).

At the end of the script genproj.bat the -target=%VCVER% should be replaced by -target=cbp to generate Code::Blocks project files:

%TCL_EXEC% %~dp0adm/start.tcl genproj -path=. -target=cbp

After that, the Code::Blocks workspace should be started by codeblocks.bat script. Mingw should be configured within Code::Blocks itself. Activate project DRAWEXE within workspace to launch Draw Harness directly from Code::Blocks. The project files generated in this way will be portable - you will need only to call genconf.bat (or to edit custom.bat to use relative paths) when moving OCCT to another computer.

Conclusion

OCCT can be built on one more platform - using MinGW for Windows target. If you are using MinGW - please share your experience. Kirill