Category Archives: Software Construction

Software construction, tools and goals

Sorting source files and projects in folders with CMake and Visual Studio/Xcode

Sometimes Visual Studio and Xcode projects just get out of hand. The private project I’m working on has 130 subprojects, all in a single solution, that’s just too much to display in one window. And then I learnt that projects can actually be moved to folders, just like what is possible for files in a project (so you don’t have Source Files and Header Files, but something custom, for instance following the file hierarchy).

They are activated differently, and it’s sometimes not as straightforward, but it works great once it is set up. And as this works for Xcode projects and Visual Studio projects, I was really eager to sort out my Audio Toolkit main project, so it will be the basis of the tests here.

Continue reading Sorting source files and projects in folders with CMake and Visual Studio/Xcode

Substitution in a variant dir with Scons

A few months ago, I encountered an issue with Scons and the SubstInFile2 tool. When it is used in a variant dir, when the emitter is called, the variant dir is not yet populated. Unfortunately, the emitter tries to open the file in the variant dir, so this does not work.

The only thing to do is to use the source node in the emitter instead of the variant node. So line 112:

keys = subst_keys(str(s.srcnode()))

And this is it!

Using SCons with Eclipse (Linux)

I chose Eclipse as my new Linux IDE, instead of Konqueror + KWrite. The purpose was to be able to launch a SCons build from the IDE, get the errors in a panel and double-clicking on one of them would direct me to the location of the error.

So Eclipse seemed to fit my needs:

  • Plug-ins to add the support of various languages
  • Support of different construction tools
  • Support from the main C/C++/Fortran compiler developers (GNU, Intel, IBM, …)

So I will know show you two ways of enabling SCons support for Eclipse.
Continue reading Using SCons with Eclipse (Linux)

Creating a Python module with Scons and SWIG

Some times ago, I proposed an optional build for SWIG if the SWIG binary was not found on the system. Here I propose an enhancement, a new library builder that will be registered in the environment env as PythonModule. It takes the same arguments as a classical SharedLibrary, but it does some additional steps :

  • It forces SWIG to create a Python wrapper (flag -python)
  • It checks if SWIG is present at all
  • It suppresses every prefix that the system might need (as lib in Linux)
  • On Windows and for Python >= 2.5, it changes the extension as pyd

Continue reading Creating a Python module with Scons and SWIG

Enabling thread support in SWIG and Python

I was looking for some days in SWIG documentation how I could release the GIL (Global Interpreter Lock) with SWIG. There were some macros defined in the generated code, but none was used in any place.

In fact, I just had to enable the thread support with an additional argument (-threads) and now every wrapped function releases the GIL before it is called, but that does not satisfy me. Indeed, some of my wrappers must retain the GIL while they are used (see this item). So here are the features that can be used :

  • nothread enables or disables the whole thread lock for a function :
    • %nothread activates the nothread feature
    • %thread disables the feature
    • %clearnothread clears the feature
  • nothreadblock enables or disables the block thread lock for a function :
    • %nothreadblock activates the nothreadblock feature
    • %threadblock disables the feature
    • %clearnothreadblock clears the feature
  • nothreadallow enables or disables the allow thread lock for a function :
    • %nothreadallow activates the nothreadallow feature
    • %threadallow disables the feature
    • %clearnothreadallow clears the feature

When the whole thread lock is enabled, the GIL is locked when entering the C function (with the macro SWIG_PYTHON_THREAD_BEGIN_BLOCK). Then it is released before the call to the function (with SWIG_PYTHON_THREAD_BEGIN_ALLOW), retained after the end (SWIG_PYTHON_THREAD_END_ALLOW) and finally it is released when exiting the function (SWIG_PYTHON_THREAD_END_BLOCK), after all Python result variables are created and/or modified.

Using Scons to create Python modules with Visual Studio 2005

Starting from Visual Studio 2005, every executable or dynamic library must declare the libraries it uses with a manifest file. This manifest can be embedded in the executable or library, and this is the best way to deal with it.

When using Scons, this embedding does not occur automatically. One has to overload the SharedLibrary builder so that a post-action is made after building the library :

def MSVCSharedLibrary(env, library, sources, **args):
  cat=env.OriginalSharedLibrary(library, sources, **args)
  env.AddPostAction(cat, 'mt.exe -nologo -manifest ${TARGET}.manifest -outputresource:$TARGET;2')
  return cat
 env['BUILDERS']['OriginalSharedLibrary'] = env['BUILDERS']['SharedLibrary']
 env['BUILDERS']['SharedLibrary'] = MSVCSharedLibrary

With this method, the embedding is made for every library, which is handy. The same can be done for the Program builder with the line :

  env.AddPostAction(cat, 'mt.exe -nologo -manifest ${TARGET}.manifest -outputresource:$TARGET;1')

Building with Scons and an optional SWIG

I now regularly use Scons as a cross-platform software construction tool. It is easy, written in Python, and I know Python, so no problem learning a new language as for CMake. In some cases when I use SWIG, the target platform does not have the SWIG executable. But when compiling a module, Scons must use this executable, whatever you try to do. In this case, one need to create a new SharedLibrary builder, so that this attribute will determine if SWIG is present or if the generated .c or .cpp files must be used instead.
Continue reading Building with Scons and an optional SWIG