Jakub Jelinek commented on freenode/#gcc:
from quick look at the kernel, I'd say the kernel is buggy
I'd say used attribute is a must in the #define __videocard struct card_info
__attribute__((section(".videocards")))
because when it declares static __videocard var = { ... }; then the compiler
has all rights to just nuke those as unused
though I can't reproduce it with:
struct S { int i, j; };
static struct S __attribute__((section ("foobar"))) s = { 1, 2 };
void foo (void)
{
s.i = 2;
s.j = 3;
}
actually, the kernel code is even more insane
struct S { int i, j; void (*p) (void); };
static struct S __attribute__((section ("foobar"))) s;
static void foo (void)
{
s.i = 2;
s.j = 3;
}
static struct S __attribute__((section ("foobar"))) s = { 1, 2, foo };
if this ever worked, it was purely by accident
note that the struct var is static, not marked as used, only used (visibly to
the compiler) in a static function that is only referenced from the static
struct variable's initializer
but please tell me which gcc would not optimize that away, even 4.1 at -O2 does
seems this got broken 4 years ago though
commit a1a00b58855ccdbedf556b4f5638d5208b454472
Author: Hannes Eder <[email protected]>
Date: Sun Nov 23 19:37:09 2008 +0100
a preprocessed testcase still would be nice to see if for some reason it
happens not to be optimized out by month old 4.7 and is right now
but the reduced testcase from what I saw in the kernel code really optimizes to
nothing even in 4.1
even 3.4 does, 3.3/3.2 doesn't at -O2
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https://bugs.launchpad.net/bugs/1049650
Title:
Regression: "Undefined video mode" with 3.5.0-14.16
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