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Date: Wed, 15 Jul 2015 15:11:49 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: SIGSEGV before main ? and gcc-debuginfo
Message-ID: <20150715131149.GQ16720@calimero.vinschen.de>
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Hi Marco,


I seem to have missed this...

On Jul 11 09:22, Marco Atzeri wrote:
> trying to debug latest release candidate of netcdf
> I hit this SIGSEGV before reaching main
>=20
> $ gdb .libs/ctest.exe
> GNU gdb (GDB) Cygwin 7.9.1-1
> .....
> Reading symbols from .libs/ctest.exe...done.
> (gdb) break main
> Breakpoint 1 at 0x100401171: file
> /pub/devel/netcdf/prova/netcdf-c-4.4.0-rc2/ncdump/ctest.c, line 32.
> (gdb) run
> Starting program: /cygdrive/e/cyg_pub/devel/netcdf/prova/netcdf-c-4.4.0-r=
c2_build64/ncdump/.libs/ctest.exe
> [New Thread 9476.0x2a88]
> [New Thread 9476.0x1fa0]
> [New Thread 9476.0x9a8]
>=20
> Program received signal SIGSEGV, Segmentation fault.
> ___chkstk_ms () at
> /usr/src/debug/gcc-4.9.3-1/libgcc/config/i386/cygwin.S:146
> 146             orq     $0x0, (%rcx)            /* probe there */
>=20
> I thought it was a stack issue and I raised from 2M to 8M

It *is* a stack issue of some sort, otherwise it wouldn't have called
___chkstk_ms, which is the guard page handler.

Did you find out in the meantime?

> SizeOfStackReserve      0000000000200000
>=20
> SizeOfStackReserve      00000000007a1200
>=20
> with no success.
>=20
> May be it is not a netcdf bug ? Ideas what to look for ?

If it's prior to main, it must be some constructor.  Other than that,
no idea.

> $ uname -svr
> CYGWIN_NT-6.1 2.0.4(0.287/5/3) 2015-06-09 12:22
>=20
>=20
> In addition there is a problem with gcc-debuginfo
>=20
>  $ cygcheck -l gcc-debuginfo |grep cygwin.S
> /usr/src/debug/gcc-4.9.3-1/libgcc/config/i386/cygwin.S
>=20
> (gdb) break ___chkstk_ms
> Breakpoint 2 at 0x100407a60: ___chkstk_ms. (5 locations)
> (gdb) run
> Starting program: /cygdrive/e/cyg_pub/devel/netcdf/prova/netcdf-c-4.4.0-r=
c2_build64/ncdump/.libs/ctest.exe
> [New Thread 6656.0x2980]
>=20
> Breakpoint 2, ___chkstk_ms () at ../../../libgcc/config/i386/cygwin.S:137
> 137     ../../../libgcc/config/i386/cygwin.S: No such file or directory.

Hmm, the relative path might break finding the debuginfo.  You
should be able to help gdb by calling

  (gdb) dir /usr/src/debug/gcc-4.9.3-1/libgcc/config/i386


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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