[Bug c++/50207] New: G++ segv's on reduced test case

["bergner at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50207

             Bug #: 50207
           Summary: G++ segv's on reduced test case
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: bergner@gcc.gnu.org


A G++ from today's trunk (20110826) segv's on a reduced test case (using delta)
like so:

bergner@igoo:~> cat minimal.ii 
typedef long unsigned int size_t;
namespace std __attribute__ ((__visibility__ ("default")))
{
  using::size_t;
}

typedef unsigned char uint8_t;
namespace std
{
  namespace decimal
  {
    template < class _Fmt > struct _FmtTraits;
    class decimal32;
  }
}
namespace std
{
  namespace decimal
  {
    template <> class _FmtTraits < decimal32 >
    {
      public:
      static const std::size_t _NumBytes = 4UL;
    };
    template < class _Tr > class _DecBase
    {
      uint8_t _Bytes[_Tr::_NumBytes];
    };
    class decimal32:public _DecBase < _FmtTraits < decimal32 > >
    {
      decimal32 () { }
    };
  }
}
bergner@igoo:~> /home/bergner/gcc/install/gcc-mainline-debug/bin/g++ -Wall -S
minimal.ii 
g++: internal compiler error: Segmentation fault (program cc1plus)
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://gcc.gnu.org/bugs.html> for instructions.

GDB show this backtrace:

#0  0x0000000010412cc8 in decl_is_template_id (decl=0xfffb6edcc18,
template_info=0xfffb6edcc18)
    at /home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:267
#1  0x000000001041b44c in write_nested_name (decl=0xfffb6e24ac0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:928
#2  0x000000001041ab48 in write_name (decl=0xfffb6e24ac0, ignore_local_scope=0)
at /home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:855
#3  0x00000000104284e4 in write_class_enum_type (type=0xfffb6edd4a0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2398
#4  0x0000000010424840 in write_type (type=0xfffb6edd4a0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:1884
#5  0x000000001042d1ec in write_template_arg (node=0xfffb6edcc18) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2843
#6  0x0000000010428868 in write_template_args (args=0xfffb6f13a70) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2427
#7  0x000000001041b50c in write_nested_name (decl=0xfffb6e245b8) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:932
#8  0x000000001041ab48 in write_name (decl=0xfffb6e245b8, ignore_local_scope=0)
at /home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:855
#9  0x00000000104284e4 in write_class_enum_type (type=0xfffb6edccc0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2398
#10 0x0000000010424840 in write_type (type=0xfffb6edccc0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:1884
#11 0x000000001042d1ec in write_template_arg (node=0xfffb6edccc0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2843
#12 0x0000000010428868 in write_template_args (args=0xfffb6f14088) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2427
#13 0x000000001041b50c in write_nested_name (decl=0xfffb6e24ac0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:932
#14 0x000000001041ab48 in write_name (decl=0xfffb6e24ac0, ignore_local_scope=0)
at /home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:855
#15 0x00000000104284e4 in write_class_enum_type (type=0xfffb6edd4a0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2398
#16 0x0000000010424840 in write_type (type=0xfffb6edd4a0) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:1884
#17 0x000000001042d1ec in write_template_arg (node=0xfffb6edcc18) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2843
#18 0x0000000010428868 in write_template_args (args=0xfffb6f13a70) at
/home/bergner/gcc/gcc-mainline-base/gcc/cp/mangle.c:2427
...

The backtrace also show we have 10's of thousands of frames stacked repeated
over and over, so it looks like we've gone into some type of infinite
recursion.  A quick look at GCC 4.6 show's it fails in the same manner.  I
haven't checked anything earlier.