Python scons building - c++

Question

Now I am studying an open source fluid simulation called pabalos. I have some problems building my own program that links against the library.
The library is built from source using scons.
The directory of the project is :
[fred#suck palabos-v1.1r0]$ls
codeblocks/ examples/ jlabos/ pythonic/ SConstruct utility/
COPYING externalLibraries/ lib/ scons/ src/
I will refer to this as the project root directory!
The project's official building documentation says:
The library Palabos makes use of an on-demand compilation process. The
code is compiled the first time it is used by an end-user application,
and then automatically re-used in future, until a new compilation is
needed due to a modification of the code or compilation options.
In the examples directory, there are some example code directories, such as :
[fred#suck palabos-v1.1r0]$ls examples/showCases/rectangularChannel3d/*
examples/showCases/rectangularChannel3d/Makefile
examples/showCases/rectangularChannel3d/rectangularChannel3D.cpp
The Makefile of the example is:
[fred#suck rectangularChannel3d]$cat Makefile
##########################################################################
## Makefile for the Palabos example program rectangularChannel3D.
##
## The present Makefile is a pure configuration file, in which
## you can select compilation options. Compilation dependencies
## are managed automatically through the Python library SConstruct.
##
## If you don't have Python, or if compilation doesn't work for other
## reasons, consult the Palabos user's guide for instructions on manual
## compilation.
##########################################################################
# USE: multiple arguments are separated by spaces.
# For example: projectFiles = file1.cpp file2.cpp
# optimFlags = -O -finline-functions
# Leading directory of the Palabos source code
palabosRoot = ../../..
# Name of source files in current directory to compile and link with Palabos
projectFiles = rectangularChannel3D.cpp
# Set optimization flags on/off
optimize = true
# Set debug mode and debug flags on/off
debug = false
# Set profiling flags on/off
profile = false
# Set MPI-parallel mode on/off (parallelism in cluster-like environment)
MPIparallel = true
# Set SMP-parallel mode on/off (shared-memory parallelism)
SMPparallel = false
# Decide whether to include calls to the POSIX API. On non-POSIX systems,
# including Windows, this flag must be false, unless a POSIX environment is
# emulated (such as with Cygwin).
usePOSIX = true
# Path to external libraries (other than Palabos)
libraryPaths =
# Path to inlude directories (other than Palabos)
includePaths =
# Dynamic and static libraries (other than Palabos)
libraries =
# Compiler to use without MPI parallelism
serialCXX = g++
# Compiler to use with MPI parallelism
parallelCXX = mpicxx
# General compiler flags (e.g. -Wall to turn on all warnings on g++)
compileFlags = -Wall -Wnon-virtual-dtor
# General linker flags (don't put library includes into this flag)
linkFlags =
# Compiler flags to use when optimization mode is on
optimFlags = -O3
# Compiler flags to use when debug mode is on
debugFlags = -g
# Compiler flags to use when profile mode is on
profileFlags = -pg
##########################################################################
# All code below this line is just about forwarding the options
# to SConstruct. It is recommended not to modify anything there.
##########################################################################
SCons = $(palabosRoot)/scons/scons.py -j 2 -f $(palabosRoot)/SConstruct
SConsArgs = palabosRoot=$(palabosRoot) \
projectFiles="$(projectFiles)" \
optimize=$(optimize) \
debug=$(debug) \
profile=$(profile) \
MPIparallel=$(MPIparallel) \
SMPparallel=$(SMPparallel) \
usePOSIX=$(usePOSIX) \
serialCXX=$(serialCXX) \
parallelCXX=$(parallelCXX) \
compileFlags="$(compileFlags)" \
linkFlags="$(linkFlags)" \
optimFlags="$(optimFlags)" \
debugFlags="$(debugFlags)" \
profileFlags="$(profileFlags)" \
libraryPaths="$(libraryPaths)" \
includePaths="$(includePaths)" \
libraries="$(libraries)"
compile:
python $(SCons) $(SConsArgs)
clean:
python $(SCons) -c $(SConsArgs)
/bin/rm -vf `find $(palabosRoot) -name '*~'`
I know this makefile will call scons, and SConstruct file is in the project root dir as I have shown.
The SContstruct file is :
[fred#suck palabos-v1.1r0]$cat SConstruct
###########################################################
# Configuration file for the compilation of Palabos code,
# using the SConstruct library.
# IT IS NOT RECOMMENDED TO MODIFY THIS FILE.
# Compilation should be personalized by adjusting the
# Makefile in the directory of the main source files.
# See Palabos examples for sample Makefiles.
###########################################################
import os
import sys
import glob
argdict = dict(ARGLIST)
# Read input parameters
palabosRoot = argdict['palabosRoot']
projectFiles = Split(argdict['projectFiles'])
optimize = argdict['optimize'].lower() == 'true'
debug = argdict['debug'].lower() == 'true'
profile = argdict['profile'].lower() == 'true'
MPIparallel = argdict['MPIparallel'].lower() == 'true'
SMPparallel = argdict['SMPparallel'].lower() == 'true'
usePOSIX = argdict['usePOSIX'].lower() == 'true'
serialCXX = argdict['serialCXX']
parallelCXX = argdict['parallelCXX']
compileFlags = Split(argdict['compileFlags'])
linkFlags = Split(argdict['linkFlags'])
optimFlags = Split(argdict['optimFlags'])
debugFlags = Split(argdict['debugFlags'])
profileFlags = Split(argdict['profileFlags'])
libraryPaths = Split(argdict['libraryPaths'])
includePaths = Split(argdict['includePaths'])
libraries = Split(argdict['libraries'])
# Read the optional input parameters
try:
dynamicLibrary = argdict['dynamicLibrary'].lower() == 'true'
except:
dynamicLibrary = False
try:
srcPaths = Split(argdict['srcPaths'])
except:
srcPaths = []
flags = compileFlags
allPaths = [palabosRoot+'/src'] + [palabosRoot+'/externalLibraries'] + includePaths
if optimize:
flags.append(optimFlags)
if debug:
flags.append(debugFlags)
flags.append('-DPLB_DEBUG')
if profile:
flags.append(profileFlags)
linkFlags.append(profileFlags)
if MPIparallel:
compiler = parallelCXX
flags.append('-DPLB_MPI_PARALLEL')
else:
compiler = serialCXX
if SMPparallel:
flags.append('-DPLB_SMP_PARALLEL')
if usePOSIX:
flags.append('-DPLB_USE_POSIX')
env = Environment ( ENV = os.environ,
CXX = compiler,
CXXFLAGS = flags,
LINKFLAGS = linkFlags,
CPPPATH = allPaths
)
if dynamicLibrary:
LibraryGen = env.SharedLibrary
else:
LibraryGen = env.Library
sourceFiles = []
for srcDir in glob.glob(palabosRoot+'/src/*'):
sourceFiles.extend(glob.glob(srcDir+'/*.cpp'))
for srcDir in srcPaths:
sourceFiles.extend(glob.glob(srcDir+'/*.cpp'))
sourceFiles.extend(glob.glob(palabosRoot+'/externalLibraries/tinyxml/*.cpp'));
if MPIparallel:
palabos_library = LibraryGen( target = palabosRoot+'/lib/plb_mpi',
source = sourceFiles )
else:
palabos_library = LibraryGen( target = palabosRoot+'/lib/plb',
source = sourceFiles )
local_objects = env.Object(source = projectFiles)
all_objects = local_objects + palabos_library
env.Program(all_objects, LIBS=libraries, LIBPATH=libraryPaths)
My problem is:
When I changed the source file rectangularChannel3D.cpp in the example dir,
and run make, the palabos library should not be rebuilt since I didn't change
the library project's source file (in the 'src' dir of the root dir) at all. But
actually the lib file "libplb.a" had been rebuilt!! So why?

Answer 1

I agree with Brady. Try contacting the project you're trying to build.
Alternatively, if you get no help from them, and/or really want to fix this yourself, SCons has a flag --debug=explain which will tell you why any object is being build/rebuilt.