https://bugs.llvm.org/show_bug.cgi?id=41226
Bug ID: 41226
Summary: __builtin_wmemchr does not work with clang-cl
Product: clang
Version: 8.0
Hardware: PC
OS: other
Status: NEW
Severity: release blocker
Priority: P
Component: C++'17
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
int main()
{
static_assert(__has_feature(cxx_constexpr_string_builtins)); // is true
static_assert(__has_builtin(__builtin_wmemchr)); // is true
static_assert(!__builtin_wmemchr(nullptr, 0, 0)); // is true
__builtin_wmemchr(nullptr, 0, 0); // no error reported
}
This program does not compile.
link.exe reports this error:
LNK2019 unresolved external symbol _wmemchr referenced in function _main
lld-link.exe reports this error:
undefined symbol: _wmemchr
This issue is related to Bug 37911
(https://bugs.llvm.org/show_bug.cgi?id=37911#c1) reported by Stephan Lavavej
from Microsoft.
It seems that if __builtin_wmemchr is not forced to be evaluated at compile
time it is not "called" and clang emits the symbol _wmemchr instead. But
Microsoft's libraries do not have that symbol.
I think this is a bug. clang should be able to "call" its builtin function at
both compile time and run-time.
Maybe this is a leftover from previous clang versions, that is, before wmemchr
was made constexpr and builtin?
I tested this in VS 2017 and 2019 RC with the LLVM Compiler Toolchain
extension.
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