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Date: Fri, 30 Oct 2015 20:18:26 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Segmentation fault before main
Message-ID: <20151030191826.GQ5319@calimero.vinschen.de>
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On Oct 30 16:25, Marco Atzeri wrote:
> Hi Corinna,
>=20
> as mention some time ago, testing netcdf 4.4.0 release candidates
> I see a puzzling SIGSEGV before reaching main, so something goes wrong
> on cygwin loading/inizialization of the program.
>=20
> It happens in a simple test programs that is linked to
> cygnetcdf-7.dll and its only job is to create a test file
> called ctest0.nc.
>=20
> Previous 4.3.3.1 test case runs fine.
> The new ctest.c fails both with the new and with the old library.
> Test case and binaries are here :
>   http://matzeri.altervista.org/works/segfault/
>=20
> $ gcc ctest.c -o ctest.exe -lnetcdf
>=20
> $ gdb ./ctest.exe
> (gdb) break main
> Breakpoint 1 at 0x100401171
> (gdb) run
> Starting program: /cygdrive/e/cyg_pub/devel/netcdf/tests/ctest-440.exe
> [New Thread 8404.0x18f4]
> [New Thread 8404.0xa8c]
> [New Thread 8404.0x2270]
>=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
>=20
> $ uname -svrm
> CYGWIN_NT-6.1 2.2.1(0.289/5/3) 2015-08-20 11:42 x86_64
>=20
>=20
> libnetcdf-devel                         4.3.3.1-2
> libnetcdf7                              4.3.3.1-2
> netcdf                                  4.3.3.1-2
> netcdf-debuginfo                        4.3.3.1-2
>=20
>=20
> Unfortunately I have no clue about this code:
>=20
> /* ___chkstk_ms is a *special* function call, which uses %rax as the
> argument.
>    We avoid clobbering any registers.  Unlike ___chkstk, it just probes t=
he
>    stack and does no stack allocation.  */
>         .global ___chkstk_ms
> #ifdef __x86_64__
>         cfi_startproc()
> ___chkstk_ms:
>         pushq   %rcx                    /* save temps */
>         cfi_push(%rcx)
>         pushq   %rax
>         cfi_push(%rax)
>         cmpq    $0x1000, %rax           /* > 4k ?*/
>         leaq    24(%rsp), %rcx          /* point past return addr */
>         jb      2f
>=20
> 1:      subq    $0x1000, %rcx           /* yes, move pointer down 4k */
>         orq     $0x0, (%rcx)            /* probe there */
>=20
> Any help will be really appreciated.

Well, it's a stack probe.  It's typically called when trying to allocate
big datastructures on the stack, e.g. with alloca.  Did you try to raise
the default stacksize in the executable header (see peflags -x and -X
options).  There's not much else to work with...


HTH,
Corinna

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

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