Re: [c/4053] Re: problems debugging gcc

Re: [c/4053] Re: problems debugging gcc

[mike stump]

> 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;
--------------

Re: [c/4053] Re: problems debugging gcc

[Neil Booth]

mike stump wrote:-

> 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.

Sorry, it didn't change anything for me.

Neil.

Re: c/4053 Re: problems debugging gcc

[Daniel Jacobowitz]

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

Re: [c/4053] Re: problems debugging gcc

[Neil Booth]

Daniel Jacobowitz wrote:-

> 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.

Cool!  This looks like it.  I'll take a closer look and post a patch
if it works.

Thanks a lot for the detective work!

Neil.

[c/4053] Re: problems debugging gcc

[Daniel Jacobowitz]

On Tue, Dec 04, 2001 at 08:34:54PM +0000, Neil Booth wrote:
> mike stump wrote:-
> 
> > Yes.  Step through bison.simple a couple hundred times, and you'll
> > discover that most of the time, it spends it's time in about two to
> > four places you care about.  One place, is dispatching to actions.  It
> > can be felt, by noticing the line (at least in bison 1.25):
> 
> Have you noticed that you often get the debugger trying to step to a
> line in bison.simple that is in fact in parse.y, and complaining about
> a line out range?

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.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer