[LLVMbugs] [Bug 15054] New: 32bit Build always write's snan

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=15054

             Bug #: 15054
           Summary: 32bit Build always write's snan
           Product: clang
           Version: 3.2
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: trev.norris at gmail.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Have a problem that signaling nan's are always written when built with -m32.
Test case (original here: https://gist.github.com/0c340629e451ff31ef66)


#include <limits>
#include <cstdio>
#include <cstring>

int main()
{
  union {
    unsigned char b[sizeof(double)];
    double d;
    float f;
  } u;
  memset(&u, 0, sizeof(u));
  u.f = std::numeric_limits<float>::signaling_NaN(); //__builtin_nansf("");
  printf("%02x %02x %02x %02x %02x %02x %02x %02x\n",
         u.b[0], u.b[1], u.b[2], u.b[3],
         u.b[4], u.b[5], u.b[6], u.b[7]);
  u.f = std::numeric_limits<float>::quiet_NaN(); //__builtin_nanf("");
  printf("%02x %02x %02x %02x %02x %02x %02x %02x\n",
         u.b[0], u.b[1], u.b[2], u.b[3],
         u.b[4], u.b[5], u.b[6], u.b[7]);
  u.d = std::numeric_limits<double>::signaling_NaN(); //__builtin_nans("");
  printf("%02x %02x %02x %02x %02x %02x %02x %02x\n",
         u.b[0], u.b[1], u.b[2], u.b[3],
         u.b[4], u.b[5], u.b[6], u.b[7]);
  u.d = std::numeric_limits<double>::quiet_NaN(); //__builtin_nan("");
  printf("%02x %02x %02x %02x %02x %02x %02x %02x\n",
         u.b[0], u.b[1], u.b[2], u.b[3],
         u.b[4], u.b[5], u.b[6], u.b[7]);
}


$ for CXX in clang++ g++; do for M in 32 64; do $CXX -m$M -o tmp/snan-$CXX$M
tmp/snan.cc; echo "*** $CXX $M bits"; tmp/snan-$CXX$M; done; done
*** clang++ 32 bits
00 00 c0 ff 00 00 00 00
00 00 c0 ff 00 00 00 00
00 00 00 00 00 00 f8 ff
00 00 00 00 00 00 f8 ff
*** clang++ 64 bits
00 00 a0 7f 00 00 00 00
00 00 c0 7f 00 00 00 00
00 00 00 00 00 00 f4 7f
00 00 00 00 00 00 f8 7f
*** g++ 32 bits
00 00 e0 7f 00 00 00 00
00 00 c0 7f 00 00 00 00
00 00 00 00 00 00 fc 7f
00 00 00 00 00 00 f8 7f
*** g++ 64 bits
00 00 a0 7f 00 00 00 00
00 00 c0 7f 00 00 00 00
00 00 00 00 00 00 f4 7f
00 00 00 00 00 00 f8 7f

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