http://llvm.org/bugs/show_bug.cgi?id=2959
Summary: Miscompilation of expression with multiple side-effects
Product: tools
Version: trunk
Platform: PC
OS/Version: Linux
Status: NEW
Severity: normal
Priority: P2
Component: llvm-gcc
AssignedTo: [EMAIL PROTECTED]
ReportedBy: [EMAIL PROTECTED]
CC: [email protected]
Created an attachment (id=2141)
--> (http://llvm.org/bugs/attachment.cgi?id=2141)
Resulting bitcode
When the following code is compiled with llvm-gcc and run
int *p;
int f() {
(*p)++;
return 1;
}
int main() {
int b;
p = &b;
b++ + f();
return (b == 2) ? 0 : 1;
}
it returns 1. Even though the order of evaluation of the operands of add is
undefined, I believe the result is well defined since the call to f is a
sequence point. Either b++ is executed first in which case the increment of b
must complete before the call to f() or f() is executed first in which case the
increment of (*p) must complete by the end of the 1st statement in f(). Either
way b should end up with the value 2, giving an expected return value of 0.
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