Defining C++ Preprocessor macros with SCons

Question

I'm trying to define a preprocessor macro within Scons for building a larger C/C++ project.

One of the libraries I'm using needs ALIGN defined. To be more specific, if I add

#define ALIGN(x) __attribute((aligned(x)))

to the header file of said library, it compiles fine. However, I should be able to specify this at build time, as this is how the library intends on being used. I know in CMake, I would be able to define the macro using something like

SET(ALIGN_DECL "__attribute__((aligned(x)))") 

Defining constants in Scons like this

myEnv.Append(CPPDEFINES = ['IAMADEFINEDCONSTANT']) 

works fine, but definine a macro in this way doesn't work. What gives?

Edit: fixed typo

Answer 1

I was able to do it on Linux with g++ as follows:

SConscript

env = Environment()
env.Append(CPPDEFINES=['MAX(x,y)=(x>y ? x:y)'])
env.Program(target = 'main', source = 'main.cc')

main.cc

#include <iostream>

using namespace std;

int main(int argc, char **argv)
{
  int a = 3;
  int b = 5;

  // MAX() will be defined at compile time
  cout << "Max is " << MAX(a, b) << endl;
}

Compilation

$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
g++ -o main.o -c "-DMAX(x,y)=(x>y ? x:y)" main.cc
g++ -o main main.o
scons: done building targets.

Execution

./main
Max is 5