http://llvm.org/bugs/show_bug.cgi?id=16940
Bug ID: 16940
Summary: No warning and incorrect optimization
Product: clang
Version: 3.2
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following (bad) code compiles and links with no warnings or errors. With
any level of optimization enabled it returns the wrong result.
////////// main.c
#include <stdio.h>
#define bool int
bool isBroken();
int main(int argc, const char * argv[]) {
bool broken = isBroken();
printf("broken? %s", broken ? "true" : "false");
}
///////// broken.c
#include <stdbool.h>
bool isBroken() {
return false;
}
Without optimization this prints: "broken? false"
With any level of optimization this prints: "broken? true"
In essence, one file is compiled with bool as a 1 byte datatype and the other
as a 4 byte datatype. I realize that the fundamental issue is that the
function prototype lied about the function definition. I'm just surprised that
it didn't generate warnings or errors and that it fooled the optimizer.
This is on a Mac using xCode 4.6.3
Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin12.4.0
Thread model: posix
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