[cfe-dev] Specific clang-cl preprocessor emulation problem

[James Dennett via cfe-dev]

On Fri, Apr 15, 2016 at 3:04 PM, Edward Diener via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> I have reported bug 27380 located at
> https://llvm.org/bugs/show_bug.cgi?id=27380 for a clang-cl preprocessor
> problem as it emulates the VC++ preprocessor. The problem can be
> illustrated wit the code:
>
> #define TEST_MACRO(x,y) TEST_EXPAND(2, 0, TEST_SOMETHING(x,y,1))
> #define TEST_SOMETHING(x,y,z) 2
>
> #define TEST_EXPAND(...) TEST_EXPAND_I(TEST_OVR(TEST_NAME, __VA_ARGS__),
> (__VA_ARGS__))
> #define TEST_OVR(name,...) TEST_SOMENAME
> #define TEST_EXPAND_I(m, args) TEST_EXPAND_II(m, args)
> #define TEST_EXPAND_II(m, args) TEST_CAT(m ## args,)
> #define TEST_SOMENAME(x,y,z) ;
>
> #define TEST_CAT(a, b) TEST_CAT_I(a, b)
> #define TEST_CAT_I(a, b) TEST_CAT_II(~, a ## b)
> #define TEST_CAT_II(p, res) res
>
> int main()
>         {
>         TEST_MACRO(1,2)
>     }
>
> which compiles correctly with VC++14 but with the latest clang-cl built
> from the trunk gives:
>
> test_clang.cpp(17,2):  error: pasting formed 'TEST_SOMENAME(', an invalid
> preprocessing token [-Winvalid-token-paste]
>         TEST_MACRO(1,2)
>         ^
> test_clang.cpp(2,25):  note: expanded from macro 'TEST_MACRO'
> #define TEST_MACRO(x,y) TEST_EXPAND(2, 0, TEST_SOMETHING(x,y,1))
>                         ^
> test_clang.cpp(5,26):  note: expanded from macro 'TEST_EXPAND'
> #define TEST_EXPAND(...) TEST_EXPAND_I(TEST_OVR(TEST_NAME, __VA_ARGS__),
> (__VA_ARGS__))
>                          ^
> test_clang.cpp(7,32):  note: expanded from macro 'TEST_EXPAND_I'
> #define TEST_EXPAND_I(m, args) TEST_EXPAND_II(m, args)
>                                ^
> test_clang.cpp(8,44):  note: expanded from macro 'TEST_EXPAND_II'
> #define TEST_EXPAND_II(m, args) TEST_CAT(m ## args,)
>
> The bug is instrumental in keeping Boost PP from working correctly with
> clang-cl, and therefore keeping many other Boost libraries, which use Boost
> PP, from working with clang-cl. There appear to be other problems but until
> this gets fixed I won't know for sure, since fixing this problem may make
> any others which have shown up go away.
>
> Thanks for listening !
>

Did you try disabling -Winvalid-token-paste (-Wno-invalid-token-paste)?
Possibly it should be disabled by default in MSVC emulation mode, but
macro_paste_identifier_error.c explicitly turns it off as well as
specifying -fms-extensions.

-- James
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