https://llvm.org/bugs/show_bug.cgi?id=30806
Bug ID: 30806
Summary: Wrong code generation at -O2 leading to division by
zero
Product: new-bugs
Version: 3.9
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: cl...@martinien.de
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 17500
--> https://llvm.org/bugs/attachment.cgi?id=17500&action=edit
Repro
Attached repro causes a division by zero although it shouldn't (I tried my best
to rule out undefined behavior, but if I missed something let me know).
Build with build.sh and run "div_by_zero"
In run.cpp "array" is only being assigned a non-NULL pointer when both a and b
are both > 0:
if(a > 0 && b > 0) // false at runtime!
{
try {
array.reset(new size_t[b]());
}
catch (...)
{
}
}
But later on the following code gets executed even though array.get() must
return NULL:
if (array.get() != 0) // Should be false at runtime; even adding "&& a > 0"
here does not help
{
// Also this crashes:
//const size_t partSize = a != 0 ? b / a : 0;
const size_t partSize = b / a; // Crash here - Division by zero
Side note:
It works at -O1. I know that for earlier clang versions (I think 3.6) this
broke even at -O1, but the workaround seen above ("Also this crashes") worked
there.
Best regards,
Martin
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