Question

I have this SConstruct file:

env=Environment()
env.Append(CCFLAGS = ['-std=c99', '-Wall', '-Wextra', '-g'])
print env["CCFLAGS"]


#Program('test_array.c',CCFLAGS=['-std=c99', '-Wall', '-Wextra', '-g'],
                                                   CPPPATH = '.', LIBS='stuff', LIBPATH=".")

#Program('test_array.c',CPPPATH = '.', LIBS='stuff', LIBPATH=".")

The output from uncommenting the first Program() is:

scons
scons: Reading SConscript files ...
-std=c99 -Wall -Wextra -g
scons: done reading SConscript files.
scons: Building targets ...
gcc -o test_array.o -c -std=c99 -Wall -Wextra -g -I. test_array.c
gcc -o test_array test_array.o -L. -lstuff
scons: done building targets.

The output from uncommenting the second Program() is:

scons
scons: Reading SConscript files ...
-std=c99 -Wall -Wextra -g
scons: done reading SConscript files.
scons: Building targets ...
gcc -o test_array.o -c -I. test_array.c
test_array.c: In function 'test_insert':
test_array.c:85:4: error: 'for' loop initial declarations are only allowed in C99 mode
test_array.c:85:4: note: use option -std=c99 or -std=gnu99 to compile your code

The env variable has a value for CCFLAGS but I don’t know why it isn’t being used when not explicitly specified in the Program() call.

Answer 1

The Program() builder is taking the construction variables from the DefaultEnvironment(), not from the env you created. This behavior is described here.

Try the following:

env=Environment()
env.Append(CCFLAGS = ['-std=c99', '-Wall', '-Wextra', '-g'])
print env["CCFLAGS"]

# Program() will take the construction vars from env, not the DefaultEnvironment()
#env.Program('test_array.c',CCFLAGS=['-std=c99', '-Wall', '-Wextra', '-g'],
                                                   CPPPATH = '.', LIBS='stuff', LIBPATH=".")

#env.Program('test_array.c',CPPPATH = '.', LIBS='stuff', LIBPATH=".")

Notice I call the Program() builder on the env you created and modified.

So, all you really need is the second call, as follows:

env=Environment()
env.Append(CCFLAGS = ['-std=c99', '-Wall', '-Wextra', '-g'])
print env["CCFLAGS"]

# Program() will take the construction vars from env, not the DefaultEnvironment()
env.Program('test_array.c',CPPPATH = '.', LIBS='stuff', LIBPATH=".")