SCONS: How do I carry on an action on a target in place

Question

Let's say I want to strip all the debug symbols in the shared libraries that I build whiling keeping the original file name.

I tried to add an command in the method:

def mySharedLibrary(self, *args, **kwargs):
    # do some common work for every shared library like add a soname or append some lib files to LIBS      parameter
     target = SharedLibary(*args, **kwargs)
     target = env.Command(target,target, "objcopy --strip-debug ${SOURCE}")
     return target

I get this error: two different method was given to the same target, I guess it's because the two targets returned by env.Command and SharedLibrary are exactly the same name.

Any ideas to do this?

Thanks in advance!

Answer 1

I had the same problem and got the same error. What I had to do was to create an intermediate target/library. The intermediate and final targets each had their own library name, so SCons doesnt get confused.

You could probably do something like the following:

env.SharedLibrary(target = 'namePreStrip', source = 'yourSource')
env.Command(target = 'name', source = 'namePreStrip', 'objcopy...')

I used objcopy to build a library out of several libraries. Here's the actual source code I implemented:

#
# Build an object file out of several other source files, objects, and libraries
# Optionally execute objcopy on the resulting library, depending if objcopyFlags
# has been populated
#
# env - SCons Environment used to build, Mandatory arg
# target - resulting library name, without LIBPREFIX and LIBSUFFIX, ej 'nsp2p',
#          Mandatory arg
# sourceFiles - list of '.cc' files that will be compiled and included in the
#               resulting lib, Optional arg
# objects - list of already compiled object files to be included in resulting lib,
#           Optional arg
# libraries - list of libraries to be included in resulting lib, Optional arg
# objcopyFlags - list of flags to pass to objcopy command. objcopy will only
#                be executed if this list is populated, Optional arg
# 
# One of [sourceFiles, objects, or libraries] must be specified, else nothing
# will be performed
#
# Not using a custom builder because I dont like the way SCons prints the
# entire command each time its called, even if its not going to actually
# build anything AND I need more method args than provided by custom builders
#
def buildWholeArchive(self, env, target, sourceFiles, objects, libraries, objcopyFlags):
    if len(sourceFiles) == 0 and len(objects) == 0 and len(libraries) == 0:
        print "Incorrect use of buildWholeArchive, at least one of [sourceFiles | objects | librarires] must be specified, no build action will be performed"
        return None

    # Compile each source file
    objNodes = []
    if len(sourceFiles) > 0:
        objNodes = env.Object(source = sourceFiles)

    cmdList = []
    cmdList.append(env['CXX'])
    cmdList.append('-nostdlib -r -o $TARGET -Wl,--whole-archive')
    for obj in objNodes:
        cmdList.append(env.File(obj).abspath)
    for obj in objects:
        cmdList.append(env.File(obj).abspath)
    for lib in libraries:
        cmdList.append(lib)
    cmdList.append('-Wl,--no-whole-archive')
    cmd = ' '.join(cmdList)

    libTarget = '%s%s%s' % (env['LIBPREFIX'], target, env['LIBSUFFIX'])

    if len(objcopyFlags) > 0:
        # First create the library, then run objcopy on it
        objTarget = '%s%s_preObjcopy%s' % (env['LIBPREFIX'], target, env['LIBSUFFIX'])
        preObjcopyTarget = env.Command(target = objTarget, source = [], action = cmd)
        env.Depends(preObjcopyTarget, [objNodes, sourceFiles, objects, libraries])

        objCmdList = [env['OBJCOPY']]
        objCmdList.extend(objcopyFlags)
        objCmdList.append('$SOURCE $TARGET')
        objcopyCmd = ' '.join(objCmdList)
        archiveTarget = env.Command(target = libTarget, source = preObjcopyTarget, action = objcopyCmd)
    else:
        # Just create the library
        archiveTarget = env.Command(target = libTarget, source = [], action = cmd)
        env.Depends(archiveTarget, [objNodes, sourceFiles, objects, libraries])

    return archiveTarget

And here is how I called it:

sourceFiles = ['file1.cc', 'file2.cc']
libSource = []
if 'OcteonArchitecture' in env:
    libSource.append(lib1)
    libSource.append(lib2)
libSource.append(lib3)

objcopy = []
if 'OcteonArchitecture' in env:
    objcopy.extend([
        '--redefine-sym calloc=ns_calloc',
        '--redefine-sym free=ns_free',
        '--redefine-sym malloc=ns_malloc',
        '--redefine-sym realloc=ns_realloc'])

archiveTarget = clonedEnv.buildWholeArchive(target = libName,
                                            sourceFiles = sourceFiles,
                                            objects = [],
                                            libraries = libSource,
                                            objcopyFlags = objcopy)
env.Alias('libMyLib', archiveTarget)