Re: c/4053 Re: problems debugging gcc

[Daniel Jacobowitz <drow at mvista dot com>]

The following reply was made to PR c/4053; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: mike stump <mrs@windriver.com>
Cc: neil@daikokuya.demon.co.uk, danishsamad@yahoo.com,
	gcc-gnats@gcc.gnu.org, gcc@gcc.gnu.org
Subject: Re: c/4053 Re: problems debugging gcc
Date: Wed, 5 Dec 2001 18:17:39 -0500

 On Tue, Dec 04, 2001 at 05:02:14PM -0800, mike stump wrote:
 > > Date: Tue, 4 Dec 2001 16:08:45 -0500
 > > From: Daniel Jacobowitz <drow@mvista.com>
 > > To: Neil Booth <neil@daikokuya.demon.co.uk>
 > 
 > > For the curious, this is the exact same problem as c/4053.
 > 
 > > > This happens to me very frequently; I have no idea what causes it.  I
 > > > have a sneaking suspicion that this GCC bug is what the original post
 > > > was about, though I'm not sure.
 > 
 > > Well, it isn't in the debug format code; the file information in the
 > > RTL is wrong.  And there's nothing obviously incorrect about the code
 > > in cb_file_change...
 > 
 > > Aha, I think I see it.  cb_file_change updates input_filename as it
 > > reads.  Compile the testcase from the PR with a breakpoint on
 > > cb_file_change and a breakpoint on emit_line_note.  If I had to guess,
 > > I'd say that the problem was input_filename describing the state of the
 > > lexer where it used to describe the state of the parser.  In
 > > c_expand_body is the line:
 > >   init_function_start (fndecl, input_filename, DECL_SOURCE_LINE (fndecl));
 > 
 > > DECL_SOURCE_LINE is fine.  input_filename isn't.
 > 
 > Ok, since you did all the hard work, test out the below, and let us
 > know if it works.  Could someone else run a dejagnu run on it, then we
 > can submit it for inclusion.
 > 
 > 2001-12-04  Mike Stump  <mrs@wrs.com>
 > 
 > 	* c-decl.c (c_expand_body): Use the name of the file associated
 > 	with the fndecl, not the current input filename.
 > 
 > *** c-decl.c.~1~	Tue Dec  4 16:52:33 2001
 > --- c-decl.c	Tue Dec  4 16:54:14 2001
 > *************** c_expand_body (fndecl, nested_p, can_def
 > *** 6889,6895 ****
 >   
 >     /* Initialize the RTL code for the function.  */
 >     current_function_decl = fndecl;
 > !   init_function_start (fndecl, input_filename, DECL_SOURCE_LINE (fndecl));
 >   
 >     /* This function is being processed in whole-function mode.  */
 >     cfun->x_whole_function_mode_p = 1;
 > --- 6889,6897 ----
 >   
 >     /* Initialize the RTL code for the function.  */
 >     current_function_decl = fndecl;
 > !   init_function_start (fndecl,
 > ! 		       DECL_SOURCE_FILE (fndecl),
 > ! 		       DECL_SOURCE_LINE (fndecl));
 >   
 >     /* This function is being processed in whole-function mode.  */
 >     cfun->x_whole_function_mode_p = 1;
 > --------------
 
 I don't expect this to have any effect, and Neil seemed to confirm
 that.  Every reference to the input_filename global in the front-end is
 going to be similarly wrong.  See all of c-semantics, for instance.
 
 -- 
 Daniel Jacobowitz                           Carnegie Mellon University
 MontaVista Software                         Debian GNU/Linux Developer