gcc/g++ option to place all object files into separate directory

Question

I am wondering why gcc/g++ doesn\'t have an option to place the generated object files into a specified directory.

For example:

mkdir builddir
mkdir          


        

Answer 1

You can use a simple wrapper around gcc that will generate the necessary -o options and call gcc:

$ ./gcc-wrap -c file1.c file2.c file3.c --outdir=obj 
gcc -o obj/file1.o -c file1.c
gcc -o obj/file2.o -c file2.c
gcc -o obj/file3.o -c file3.c

Here is such a gcc_wrap script in its simplest form:

#!/usr/bin/perl -w

use File::Spec;
use File::Basename;
use Getopt::Long;
Getopt::Long::Configure(pass_through);

my $GCC = "gcc";
my $outdir = ".";
GetOptions("outdir=s" => \$outdir)
    or die("Options error");

my @c_files;
while(-f $ARGV[-1]){
    push @c_files, pop @ARGV;
}
die("No input files") if(scalar @c_files == 0);

foreach my $c_file (reverse @c_files){
    my($filename, $c_path, $suffix) = fileparse($c_file, ".c");
    my $o_file = File::Spec->catfile($outdir, "$filename.o");
    my $cmd = "$GCC -o $o_file @ARGV $c_file";
    print STDERR "$cmd\n";
    system($cmd) == 0 or die("Could not execute $cmd: $!");
}

Of course, the standard way is to solve the problem with Makefiles, or simpler, with CMake or bakefile, but you specifically asked for a solution that adds the functionality to gcc, and I think the only way is to write such a wrapper. Of course, you could also patch the gcc sources to include the new option, but that might be hard.