Multi-File Build

Once we have multiple source files there are a number of choices on how to build.

Assume our setup is this:

$ tree
.
├── SConstruct
├── main.c
├── message.c
└── message.h

Where message.h is:

#ifndef message_H
#define message_H

void print_message(const char * str);

#endif  // message_H

and main.c is now:

#include "message.h"

int main(void)
{
    print_message("Hello from scons");
    return 0;
}

If we rebuild now, we'd get the following error message:

$ scons
scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
gcc -o main.o -c main.c
gcc -o main main.o
Undefined symbols for architecture x86_64:
  "_print_message", referenced from:
      _main in main.o

As the build system is not including message.c

Option-1 : Quick and Dirty

The easy fix is to use the Glob pattern matching facility, e.g.

Program(source = Glob('*.c'))

This will include all files matching the pattern, i.e. all .c files in current directory in this case.

The pattern matching uses standard Unix style matchers, e.g.

*       matches everything
?       matches any single character
[seq]   matches any character in seq
[!seq]  matches any char not in seq”

Option-2 : Explicit List

As Scons is Python based, we can utilise Python lists, e.g.

Program(source = ['main.c', 'message.c'])

or alternatively:

sources=['main.c', 'message.c']
Program(source = sources)

Setting the name of the Executable

By default, scons will use the first filename in the list as the executable, e.g. if we change the SConstruct to this:

sources = ['message.c','main.c']
Program(source = sources)

the an executable called message would be generated.

We can override this behaviour by explicitly setting a target name, e.g.

sources = ['message.c','main.c']
Program(target = 'hello', source = sources)

or more explicitly:

exe = 'hello'
sources = ['message.c','main.c']
Program(target = exe, source = sources)

Which Option is best?

PLACEHOLDER FOR PROs AND CONs