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From: Marco Atzeri <marco DOT atzeri AT gmail DOT com>
Subject: Segmentation fault before main
To: "cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Message-ID: <56338BCC.40709@gmail.com>
Date: Fri, 30 Oct 2015 16:25:00 +0100
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Hi Corinna,

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.

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.

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/

$ gcc ctest.c -o ctest.exe -lnetcdf

$ 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]

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 */


$ uname -svrm
CYGWIN_NT-6.1 2.2.1(0.289/5/3) 2015-08-20 11:42 x86_64


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


Unfortunately I have no clue about this code:

/* ___chkstk_ms is a *special* function call, which uses %rax as the 
argument.
    We avoid clobbering any registers.  Unlike ___chkstk, it just probes the
    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

1:      subq    $0x1000, %rcx           /* yes, move pointer down 4k */
         orq     $0x0, (%rcx)            /* probe there */

Any help will be really appreciated.

Regards
Marco

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