http://llvm.org/bugs/show_bug.cgi?id=14973
Bug #: 14973
Summary: infinite loop optimized away
Product: clang
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected]
Classification: Unclassified
We have found an inconsistency in the following testcase (derived from
pr33992.c in the gcc testsuite) using clang 3.2 and trunk. When compiled
without optimization, the loop does not terminate. However, with -O1 or above,
clang optimizes away the loop. This behavior appears incorrect, as overflow
behavior is well defined with unsigned int. Using -fwrapv and -ftrapv does not
change this result.
$ clang -O0 reduced.c
$ ./a.out
^C [hangs]
$ clang -O1 reduced.c
$ ./a.out
$ clang -v
clang version 3.3 (trunk 172630)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ cat reduced.c
void foo ()
{
unsigned int i = 0;
for (i = 0; ; i++) { }
}
int main()
{
foo();
return 0;
}
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