On Thu, Sep 26, 2024 at 11:20:15PM +0200, Enrico via Gcc wrote:
> I am trying to understand how 'flag_pic' works.
> It is used extensively in TARGET_OPTION_OVERRIDE functions in the form 'if
> (flag_pic) ... '.
> The flags fPic and fpic have a default value of -1, so as far as I
> understand, if the two flags are not set in the command line, all 'if
> (flag_pic)' will be true because of the default value -1 (since I can see
> that flag_pic is a define to global_options.x_flag_pic)
>
> It doesn't look correct to me, but this test is used so many times that I
> am sure I am missing something.
Yes, you are missing gcc/opts.cc (finish_options)
if (!opts->x_flag_opts_finished)
{
/* We initialize opts->x_flag_pie to -1 so that targets can set a
default value. */
if (opts->x_flag_pie == -1)
{
/* We initialize opts->x_flag_pic to -1 so that we can tell if
-fpic, -fPIC, -fno-pic or -fno-PIC is used. */
if (opts->x_flag_pic == -1)
opts->x_flag_pie = (opts->x_flag_hardened
? /*-fPIE*/ 2 : DEFAULT_FLAG_PIE);
else
opts->x_flag_pie = 0;
}
/* If -fPIE or -fpie is used, turn on PIC. */
if (opts->x_flag_pie)
opts->x_flag_pic = opts->x_flag_pie;
else if (opts->x_flag_pic == -1)
opts->x_flag_pic = 0;
if (opts->x_flag_pic && !opts->x_flag_pie)
opts->x_flag_shlib = 1;
opts->x_flag_opts_finished = true;
}
The -1 value just means the state of this option hasn't been finalized yet.
Jakub
