[llvm-dev] Exceptions on Windows & MSVC

[Gaier, Bjoern via llvm-dev]

Thank you for this Aaron!

In our company we rely heavily on the compatibility between Clang-Cl and the Visual Studio compiler, lately we encountered big problems with the handling of SEH exceptions in our code, so running those tests helped us. (Sadly we can’t move to the Visual Studio compiler)

However, maybe it helps someone if I share the results from running those tests… I imported all of the tests into separated projects, compiling them with the same settings, with MSVC (v141) and Clang (9), then I compared the output. The compiler settings for all those projects were:
/permissive- /GS /GL /W3 /Gy /Zc:wchar_t /Gm- /Ox /Ob2 /sdl /Zc:inline /fp:precise /D "_MBCS" /errorReport:prompt /GF- /WX- /Zc:forScope /Gd /Oy /Oi /MD /FC /EHsc /nologo /Ot /diagnostics:classic

The MSVC compiler only failed the following test:
EH:
ihateeh.cxx

Clang however failed multiple tests:
EH:
ihateeh.cxx

SEH:
seh0007.c (-> Test failed; The access violation was optimized away, leading to a random result; – forcing the access violation caused no catching of the exception)
seh0019.c (-> No exception caught; Which makes sense because there are no catch handler, but MSVC does catch them)
seh0055.c (-> Test failed; The result is not correct)
sehframes.cpp (-> A certain exception was not caught)

The following tests didn’t even compiled, instead they crashed the compiler:
seh0034.c
seh0035.c
seh0036.c
seh0041.c
seh0042.c
seh0043.c
seh0048.c
seh0049.c
seh0050.c
xcpt4u.c

I hope that helped in some way – any comments or suggestions? I’m up for it!

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Aaron Smith via llvm-dev
Sent: 11 November 2019 23:03
To: llvm-dev at lists.llvm.org
Subject: [llvm-dev] Exceptions on Windows & MSVC

At Microsoft we open sourced some of our compiler tests for exception handling on github.
https://github.com/microsoft/compiler-tests

We are looking into what it would take to get these to work with clang-cl. I’m planning to share a design document on the mailing list soon.

Aaron


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