Bug 27954 - Exception handling info garbled on x86_64-w64-mingw32
Summary: Exception handling info garbled on x86_64-w64-mingw32
Alias: None
Product: binutils
Classification: Unclassified
Component: ld (show other bugs)
Version: 2.35.2
: P2 normal
Target Milestone: ---
Assignee: Not yet assigned to anyone
Depends on:
Reported: 2021-06-04 08:40 UTC by Dominik Strasser
Modified: 2021-06-04 08:55 UTC (History)
0 users

See Also:
Last reconfirmed:


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Description Dominik Strasser 2021-06-04 08:40:44 UTC
I am having a long standing issue with exception handling on x86_64-w64-mingw32.

The symptom is that I am getting a crash in ntdll!RtlUnwindEx when unwinding the stack between a thrown assertion and the catch handler.

I am suspecting an issue in binutils(ld) because the crash vanishes when I bind a different program with the identical objects.

I ran my program through wine which gives some additional information, namely an illegal EH information:
020c:fixme:seh:RtlVirtualUnwind unknown unwind info version 4 at 00000000080E350C
020c:fixme:seh:dump_unwind_info **** func 4cc6d40-4cc712f
020c:fixme:seh:dump_unwind_info unwind info at 00000000080E350C flags 0 prolog 0xd0 bytes function 00000000050C6D40-00000000050C712F
020c:fixme:seh:dump_unwind_info     0x1: PUSH_MACHFRAME 0
020c:fixme:seh:dump_unwind_info     0x6: pushq %rax
020c:fixme:seh:dump_unwind_info CHANIN 0

According to all documentation I found, only version 1 and 2 are legal values.
Additionally wine prints:
020c:fixme:seh:PUSH_MACHFRAME is not the last opcode.

I cannot provide an example as a lot of source code is involved, but I can compile binutils myself, and do any experiment you like.
Comment 1 Dominik Strasser 2021-06-04 08:55:07 UTC
I am chasing this bug for years, over several compiler and binutils versions. What would be helpful as a start would be some utility to dump the EH info structures from the .o file(s) and the executable. Does such an utility exist ?