Description of problem:

On very rare occasions gcc will fail to open and read the right header file.  In
the cases where we've seen it, gcc reports that the header couldn't be found -
but gcc could just as easily read the wrong header if a file with the same name
is found later in the search path, possibly resulting in silent miscompilation
of code.

The bug was introduced with this patch:
http://gcc.gnu.org/ml/gcc-bugs/2001-05/msg00141.html

Here's the whole find_or_create_entry...

find_or_create_entry (pfile, fname)
     cpp_reader *pfile;
     const char *fname;
{
  splay_tree_node node;
  struct include_file *file;
  char *name = xstrdup (fname);

  _cpp_simplify_pathname (name);
  node = splay_tree_lookup (pfile->all_include_files, (splay_tree_key) name);
  if (node)
    free (name);
  else
    {
      file = xcnew (struct include_file);
      file->name = name;
      file->err_no = errno;
      node = splay_tree_insert (pfile->all_include_files,
                                (splay_tree_key) file->name,
                                (splay_tree_value) file);
    }

  return node;
}

Note that this code assumes that errno doesn't change between
"_cpp_simplify_pathname (name)" and "file->err_no = errno;".  
Unfortunately this is not the case. On very rare occasions it is possible that
the calloc() call wrapped in "file = xcnew (struct include_file);" will set
errno even on successful calls.  The strace output of the compiler suggests that
we're expanding the heap (brk/mmap2 system calls) during this calloc() call,
which is one of the conditions under which calloc() may set errno.
gcc later will avoid trying to open the header file based on the value of
file->err_no.

I'll submit a patch that simply preserves the value of errno around the calloc()
call.

Version-Release number of selected component (if applicable):
gcc-3.2.3-59

How reproducible:
Very rarely, as it depends on the exact memory allocation pattern of the compile
run.

Steps to Reproduce:
1.Only the customer is able to reproduce by compiling their large project.
2.
3.
  
Actual results:


Expected results:


Additional info: