Sorry - I accidentally submitted the bug too soon.

So I went through debugging the assertion failure, and it seems to be because GCC was generating a LSDA for main() (.LLSDA0) with TTypeEncoding = 0x90, while the existing code expects it to be 0x0.

Copy+pasting the non-EHABI get_shim_type_info() (which can accept TTypeEncoding = 0x90) to replace the EHABI's seems to result in the exception being caught and handled properly.

So.. Does that mean there is no bug, and I should close the issue?

The bug is that the current implementation of get_shim_type_info() (for EHABI) can't handle TTypeEncoding != 0x0.

While the non-EHABI seems to be able to handle it just fine, I don't know the DWARF specification well enough such that it won't break anything else. Otherwise I would have sent a patch, not a bug report :)

llvm-mirror/libcxxabi@05d51bcf was the commit that added it, so it might be worth CCing the author

Adding Logan, since it was his commit.

IMO, 0x90 (DW_EH_PE_pcrel|DW_EH_PE_indirect), which is emitted by GCC 4.9 (or newer), is the correct value. In addition, read_target2_value() in libcxxabi are performing pc-relative indirect load actually.

However, due to a legacy reason, 0x00 (DW_EH_PE_absptr) should be supported as well. LLVM/Clang and GCC 4.6 (or earlier) are emitting 0x00. GCC changed its behavior around 2015 and that's the reason why I did not encounter this issue when I was writing those assertions.

A quick workaround is to replace the assertions in question:

assert(ttypeEncoding == DW_EH_PE_absptr && "Unexpected TTypeEncoding");

with:

assert((ttypeEncoding & 0x0f) == DW_EH_PE_absptr && "Unexpected TTypeEncoding");

I wrote those assertions because I was assuming each entry took sizeof(uintptr_t) bytes. Thus, we can replace them with a weaker assertion.

I will upload a patch for review ASAP.

Patch and test cases for this bug:

https://reviews.llvm.org/D24085

Committed as https://reviews.llvm.org/rL286760

I am closing this bug. Please let me know if this change didn't fix your problem. Thanks.