[llvm-bugs] [Bug 27334] New: Left shifting beyond sizeof int seems to have no effect.
via llvm-bugs
llvm-bugs at lists.llvm.org
Wed Apr 13 05:04:54 PDT 2016
https://llvm.org/bugs/show_bug.cgi?id=27334
Bug ID: 27334
Summary: Left shifting beyond sizeof int seems to have no
effect.
Product: clang
Version: unspecified
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: C++
Assignee: unassignedclangbugs at nondot.org
Reporter: norman.wilson at gmail.com
CC: dgregor at apple.com, llvm-bugs at lists.llvm.org
Classification: Unclassified
Best way to describe is show the code.
#include <cassert>
#include <iostream>
int
main()
{
int count = sizeof(unsigned) * 8;
unsigned x = (~0x0u) << count;
std::cout << std::hex << x << std::endl;
assert(x == 0);
}
I'd have thought that this shifting would result in x being zero or is this
undefined behaviour? This is using the following version:
bash-3.2$ clang++ --version
Apple LLVM version 7.0.2 (clang-700.1.81)
Target: x86_64-apple-darwin15.3.0
Thread model: posix
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