---code---
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
float f(1.0);
// cout << "Value: "; // works with any cout before eval!!
unsigned int i = *reinterpret_cast<unsigned int*>(&f);
cout << hex << i << endl;
cout << sizeof(float) << endl;
cout << sizeof(unsigned int) << endl;
}
--- end code ---
run w/o -O2:
bernh...@xbernhard$ c++ floatmini.cpp -o floatmini
bernh...@xbernhard$ ./floatmini
3f800000
4
4
=> works
with -O2
bernh...@xbernhard$ c++ floatmini.cpp -o floatmini -O2
bernh...@xbernhard$ ./floatmini
8048779
4
4
=> fails
* If codeline 8 is active (see comment), works too with -O2.
* unsigned int& i = reinterpret_cast<unsigned int&>(f);
fails the same way.
Is that line not standard conform?
------------------------------------
bernh...@xbernhard$ c++ -v
Using built-in specs.
Target: i486-linux-gnu
Configured with: ../src/configure -v
--enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr
--enable-shared --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix --enable-nls
--with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--disable-libmudflap --enable-targets=all --enable-checking=release
--build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu
Thread model: posix
gcc version 4.2.3 (Debian 4.2.3-2)
--
Summary: evaluation of reinterpret_cast with -O2
Product: gcc
Version: 4.2.3
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: ElGringo at gmx dot at
GCC build triplet: i486-linux-gnu
GCC host triplet: i486-linux-gnu
GCC target triplet: i486-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38855
