Compiler crash with block numbers

[Ian Lance Taylor <iant at google dot com>]

Hi Dehao, I suspect that your recent patch changing block handling has
broken bootstrap with --enable-languages=go.  I reduced the test case
to this C++ code:

#include <string>

std::string
f(bool is_string, bool is_constant)
{
  if (is_string)
    {
      std::string left_string;
      std::string right_string;
      if (is_constant)
	{
	  return left_string + right_string;
	}
    }

  return "";
}

When I compile that with current mainline with -O -g I get a crash
(the backtrace is a local patch of mine):

foo.cc: In function ‘std::string f(bool, bool)’:
foo.cc:17:1: internal compiler error: tree check: expected block, have
function_decl in change_scope, at final.c:1544
 }
 ^
0xe388bd tree_check_failed(tree_node const*, char const*, int, char const*, ...)
	../../trunk/gcc/tree.c:8892
0x50c495 tree_check(tree_node*, char const*, int, char const*, tree_code)
	../../trunk/gcc/tree.h:3659
0x9372a1 change_scope
	../../trunk/gcc/final.c:1544
0x937646 reemit_insn_block_notes
	../../trunk/gcc/final.c:1613
0x937822 final_start_function(rtx_def*, _IO_FILE*, int)
	../../trunk/gcc/final.c:1670
0x93c6ad rest_of_handle_final
	../../trunk/gcc/final.c:4291
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.


At first glance the bug is that the block obtained from insn_scope
(insn), called from reemit_insn_block_notes, has a block number of 0.
That leads to the crash in insn_scope.

It's interesting that it only occurs with -g.  I'm not sure what that means.

Could you take a look at this and see if it is due to your patch?

Thanks.

Ian