Re: next snapshot in preparation for m4 1.4.12

[Tom G. Christensen]

On Mon, Sep 01, 2008 at 07:59:50AM -0600, Eric Blake wrote:
> According to Tom G. Christensen on 8/30/2008 7:23 AM:
> 
> > configure:6499: checking for working C stack overflow detection
> > configure:6591: cc -o conftest -g -I/usr/tgcware/include -L/usr/tgcware/lib 
> > -Wl,-rpath,/usr/tgcware/lib conftest.c  >&5
> > cfe: Warning 728: conftest.c, line 62: Long double not supported; double 
> > assumed.
> >            long double ld;
> >         ---^
> 
> How annoying.  The compiler supports 'long double', per C89 (since long
> double and double are allowed to be the same type), but warns you any time
> you use it.  At any rate, that warning is ignorable (it appears in lots of
> places in your logs).
> 
I figured as much. Adding -woff 728 will silence it but it's easier to
just ignore it.

> > (dbx) t
> >>  0 recurse(p = (nil)) ["/usr/people/tgc/buildpkg/m4/src/conftest.c":96, 
> >> 0x400bec]
> >    1 recurse(p = 0x7ff0038c = "\001") 
> > ["/usr/people/tgc/buildpkg/m4/src/conftest.c":99, 0x400c10]
> >    2 recurse(p = 0x7ff005a4 = "\001") 
> > ["/usr/people/tgc/buildpkg/m4/src/conftest.c":99, 0x400c10]
> 
> Hmm, based on the pattern (each frame occupies 536 bytes), I would have
> expected the debugger to report that p = 0x7ff00174 rather than (nil) in
> the final frame before the stack overflow; but that may be a debugger
> anomaly.
>
FWIW gdb has p=0x0 so atleast it's consistent.

>I just noticed that the c-stack.m4 file doesn't check the return
> status from sigaction.  I suspect it worked for you, but just to be sure,
> could you retry this with this patch to the program in config.log:
> 
> @@ -85,8 +85,7 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
>            setrlimit (RLIMIT_STACK, &rl);
>            #endif
> 
> - -      c_stack_action ();
> - -      return recurse ("\1");
> +    return c_stack_action () && recurse ("\1");
>          }
> 
I think you hit the nail on the head.

address@hidden src]$ cc -woff 728 -o conftest-1 -g conftest-1.c
address@hidden src]$ gdb conftest-1
GNU gdb 4.17.gnat.3.11p
Copyright 1998 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "mips-sgi-irix5.3"...
(gdb) run
Starting program: /usr/people/tgc/buildpkg/m4/src/conftest-1

Program exited normally.
Current language:  auto; currently asm
(gdb)

I can replicate this on Irix 6.2 so probably the same issue there.

<snip rest of debugging instructions>
I'll return to this if you still need it.

-tgc