On Thu, Mar 23, 2017 at 7:06 PM, Ben Coman btc@openinworld.com wrote:
Probably not related, but just some things that turned up while I was browsing around...
gdb unknown target exception http://stackoverflow.com/questions/40923437/gdb-unknown-target-exception
gdb Exception in SetThreadName(unsigned long, char const*) () from /usr/bin/cygwin1.dll https://www.mail-archive.com/cygwin@cygwin.com/msg149735.html
cygwin gdb Program received signal ?, Unknown signal http://stackoverflow.com/questions/40652302/cygwin-gdb-program-received-sign...
Quick reference to Implementation... https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/include/setjmp.h https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/machine/i386/setjm... https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/machine/x86_64/set... https://github.com/Alexpux/Cygwin/blob/master/newlib/libc/include/machine/se...
btw, here is a comparison of i386 versus x86_64 Cygwin longjmp... https://www.diffchecker.com/iAMuXTMn
2015-07-21 Corinna Vinschen corinna@vinschen.de (setjmp): x86_64 only: Store tls stackptr in Frame now, store MXCSR and FPUCW registers in Spare, as MSVCRT does. (longjmp): x86_64 only: Restore tls stackptr from Frame now, restore MXCSR and FPUCW registers from Spare. 2015-06-27 Corinna Vinschen corinna@vinschen.de
- exceptions.cc (_cygtls::call_signal_handler): Drop manipulating
thread's ss_flags here. It's not safe against longjmp. https://github.com/Alexpux/Cygwin/blob/..../winsup/CVSChangeLogs.old/cygwin/...
I've been trawling the web for more candidates. This is a bit scattershot and I'm not in a position to experiment on Windows right now, but maybe useful hints for someone...
* "setjmp and longjmp (emu.c) and crashes when used in a 64bit windows environment because setjmp sets the stack register value to 0x10. Using __builtin_setjump avoids the problem because the stack register doesn't get messed (doesn't seem to call setjmp3 function of the C:\Windows\SysWOW64\msvcrt.dll library)." https://sourceforge.net/p/mingw-w64/bugs/406/
* "The problem turns out to be incorrect relocation by the internal linker ... only applies to imported symbols." Maybe why __builtin_setjump reported to work okay ?? https://github.com/golang/go/issues/13672
* probably this doesn't apply to Cygwin non-C++ code. But maybe msvcrt is written in C++ ?? ... "In portable code, when a non-local goto that calls longjmp is executed, correct destruction of frame-based objects might be unreliable." https://msdn.microsoft.com/en-us/library/yz2ez4as.aspx
* The issue is your jump from longjmp call to setjmp location is crossing functions on callstack that were created by MCJIT. Those functions do not have proper stack unwinding information required by longjmp. http://lists.llvm.org/pipermail/llvm-dev/2015-April/084889.html
* Perhaps we need to wrap exception handling around calls to functions in the msvcrt.dll ??? "Most functions that make use of the stack in 64-bit versions of Windows must support exception handling even if they make no internal use of such facilities." https://www.tortall.net/projects/yasm/manual/html/objfmt-win64-exception.htm...
* "This is a bug fix needed for 64 bit Windows. QEMU for Windows currently gets the wrong definition for sigsetjmp. It uses stack unwinding for longjmp which results in a crash when it is called from generated code. (1 Mar 2016)" https://lists.gnu.org/archive/html/qemu-devel/2016-03/msg00000.html
* I'm not sure if I understand it properly, but this seems to imply that that even pure-C (not C++) applications need to catch exceptions of OS C++ library ?? . http://ab-initio.mit.edu/octave-Faddeeva/gnulib/lib/msvc-inval.h
* "The newer runtime libraries of MSVC no longer return error codes from functions like printf(), close(), dup2(), _get_osfhandle(), when you pass an invalid format string or invalid file descriptor." https://lists.gnu.org/archive/html/bug-gnulib/2011-09/msg00239.html
* " With MSVC runtime libraries with the "invalid parameter handler" concept, Functions like fprintf(), dup2(), or close() crash when the caller passes an invalid argument. But POSIX wants error codes (such as EINVAL or EBADF) instead." http://ab-initio.mit.edu/octave-Faddeeva/gnulib/lib/msvc-inval.h
* 'The try-except statement is a Microsoft extension to the C ... language" https://msdn.microsoft.com/en-us/library/s58ftw19.aspx
cheers -ben
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Certainly look ok at the instruction that raised the exception. Looks like the longjmp is trying to return to somewhere it shouldn't. Also you've written "snip" at the hot end of the stack. If that's not a typo, post all of the hot end of the stack.
You could look at the returnToInterpreter jmpbuf after the setjmp that initializes it and become familiar with its contents. Then check when the longjmp occurs that it is t corrupted and the frame that created it still exists on the stack.
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