Failure to compile std::u16string from libstdc++ 12.1 in c++20 mode #55560
Comments
No we didn't. The relevant change is probably jwakely/gcc@5a9572e but I don't know why that would make clang not instantiate the function it calls. |
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Very odd. If I remove this function from the __attribute ((__abi_tag__ ("cxx11")))
inline basic_string<char16_t>
operator""s(const char16_t* __str, size_t __len)
{ return basic_string<char16_t>{__str, __len}; } |
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And if I remove the template<typename _FwdIterator>
constexpr
void
_M_construct(_FwdIterator __beg, _FwdIterator __end,
std::forward_iterator_tag); |
tbaederr
added
c++20
rejects-valid
libstdc++
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@llvm/issue-subscribers-c-20 |
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I think this is a small reproducer of the problem: #define INLINE constexpr
template<typename T>
INLINE
T foo(T a);
int main() {
int k = foo<int>(5);
}
template<typename T>
INLINE
T foo(T a) {
return a;
}Godbolt: https://godbolt.org/z/xoYvvbPKv The example can be fixed by defining |
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The problematic code in clang is: llvm-project/clang/lib/Sema/SemaExpr.cpp Lines 17970 to 17974 in c6ad690 Replacing that |
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https://reviews.llvm.org/D128119 seems to fix the issue |
EugeneZelenko
added
the
clang:frontend
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@llvm/issue-subscribers-clang-frontend |
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Should this be backported to the release branch? |
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@tstellar any opinion? Serge isn't available right now as far as I know. |
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/cherry-pick da6a14b |
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Failed to cherry-pick: da6a14b https://github.com/llvm/llvm-project/actions/runs/2790868798 Please manually backport the fix and push it to your github fork. Once this is done, please add a comment like this:
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This patch is already in the branch. |
They fail due to this bug: <llvm/llvm-project#55560>.
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Cherry-pick seems to fail in 14.x locally because of the ReleaseNotes.rst Is there a mean to backport in 14.x ? ( we need this in fedora 36 in order to build chromium 108). |
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There won't be any 14.x releases anymore, so you'll have to do the backport downstream |
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chromium 108 error on fedora-36 |
…non-constexpr evaluation Otherwise these functions are not instantiated and we end up with an undefined symbol. Fix llvm#55560 Differential Revision: https://reviews.llvm.org/D128119
I'm getting:
error: undefined symbol: void std::__cxx11::basic_string<char16_t, std::char_traits<char16_t>, std::allocator<char16_t> >::_M_construct<char16_t const*>(char16_t const*, char16_t const*, std::forward_iterator_tag)compiling the following simple test case:
on clang 13 and 14.0.0, with
clang++ -std=c++20 -o test test.cpp. It works fine with-std=c++17. Bizarrely, it also works if you simply uncomment theclang_string_workaroundline which isn't even called. It looks like libstdc++ moved that_M_constructfunction into a separate file recently, which might be related.The text was updated successfully, but these errors were encountered: