On Wed, 19 Jun 2002, Stas Bekman wrote:
> I cannot see this in gcc manpages, but I don't think -g implies -O0
that's not what i meant. when MP_DEBUG=1 then we drop the
$Config{optimize} flag (unless $Config{cflags} =~ -DDEBUGGING).
so with MP_DEBUG=1 there is no -On flag used when building.
pretty sure -O0 is only meant to turn off any previous -On and that no
optimizations are done unless -O1 or higher is used.
% perl test-compile.pl
out and out-O0 are the same
out-O0 and out-O1 are different
out-O1 and out-O2 are different
#test-compile.pl
use strict;
my $last = "";
my $cfile = 'test.c';
open my $fh, '>', $cfile or die;
print $fh <DATA>;
close $fh;
for my $n (undef, 0, 1, 2) {
my $o = defined $n ? "-O$n" : "";
my $file = "out";
$file .= $o if defined $n;
my $cmd = "gcc $o -S $cfile -o $file";
system $cmd;
if ($last) {
my $diff = `diff -u $file $last`;
printf "$last and $file are %s\n", $diff ? "different" : "the same";
}
$last = $file;
}
__END__
#include <stdio.h>
int main() {
if (0) {
puts("hi");
}
return 1;
}
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