http://llvm.org/bugs/show_bug.cgi?id=19138
Bug ID: 19138
Summary: wrong code (that segfaults) by LTO at all optimization
levels (affecting 3.2 till trunk)
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The current clang trunk miscompiles the following code when using LTO at all
optimization levels (-O0 to -O3) on x86_64-linux-gnu (in both 32-bit and 64-bit
modes).
It also affects clang 3.2, 3.3, and 3.4.
$ clang-trunk -v
clang version 3.5.0 (trunk 203791)
Target: x86_64-unknown-linux-gnu
Thread model: posix
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.8.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.7.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.1
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$
$ clang-trunk -O0 small.c; a.out
$
$ clang-trunk -flto -O0 small.c
$ a.out
a.out: small.c:11: int main(): Assertion `b == &a' failed.
Aborted (core dumped)
$
---------------------------------
#include <assert.h>
int a, *b, **volatile c = &b, *d = &a;
int
main ()
{
for (a = 0; a < 1; a++)
{
*c = d;
assert(b == &a);
}
return 0;
}
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