[Bug 910363] Re: miscompile writing to bitfield at -Os

[dn]

** Bug watch added: GCC Bugzilla #51759
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51759

** Also affects: gcc via
   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51759
   Importance: Unknown
       Status: Unknown

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https://bugs.launchpad.net/bugs/910363

Title:
  miscompile writing to bitfield at -Os

Status in The GNU Compiler Collection:
  Unknown
Status in “gcc-4.5” package in Ubuntu:
  New

Bug description:
  The attached preprocessed file was extracted out of a file from LLVM. When it was compiled by g++-4.5 at -Os, and LLVM's test suite was run, it resulted in the assert in PointerType's constructor firing:
  llvm::PointerType::PointerType(llvm::Type*, unsigned int): Assertion `oldNCT == NumContainedTys && "bitfield written out of bounds?"' failed.

  This was the invocation I used:
  g++-4.5 -Os -fPIC -g -pedantic -Wno-long-long -fno-exceptions -o lib/VMCore/CMakeFiles/LLVMCore.dir/Type2.cpp.o -c Type2.ii

  Further details here:
  http://llvm.org/PR11652

  ProblemType: Bug
  DistroRelease: Ubuntu 11.04
  Package: g++-4.5 4.5.2-8ubuntu4
  Uname: Linux 3.1.0-custom x86_64
  Architecture: amd64
  Date: Tue Dec 27 22:11:40 2011
  InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64 (20110427.1)
  ProcEnviron:
   LANGUAGE=en_US:en
   PATH=(custom, user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: gcc-4.5
  UpgradeStatus: No upgrade log present (probably fresh install)

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