[cxx-interop] Support _LIBCPP_PREFERRED_OVERLOAD #82019
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Xazax-hun
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| if (auto litExpr = | ||
| dyn_cast<clang::CXXBoolLiteralExpr>(clangAttr->getCond())) { | ||
| if (litExpr->getValue()) { | ||
| thisDeclHasPreferredOverload = hasPreferredOverload = true; |
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this keeps checking enable_if until one is true. The semantics of the attribute is the opposite: the function is only available if all of them evaluate to true.
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Ah okay. So are you okay with clarifying this in a comment? I don't think we want to do full enable_if evaluations here.
Some functions like memchr are defined both in libc++ and libc. Including both would result in ambiguous references at the call sites. This is worked around by an attribute that tells the compiler to prefer one overload over the others. This attribute was not interpreted by Swift. As a result, importing both libc and libc++ and calling such functions resulted in compilation errors due to ambiguous overloads. This PR modifies the lookup logic to exclude the non-preferred Clang functions from the overload set whenever a preferred overload is available. rdar://152192945
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Explanation: Some functions are implemented both in libc and libc++. Clang uses the enable_if attribute to resolve otherwise ambiguous functions calls. This PR makes the name lookup aware of this attribute. Issue: rdar://152192945 Risk: Low, only C/C++ APIs with enable_if attributes are affected. Testing: Regression test added. Original PR: #82019 Reviewer: @hnrklssn
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Some functions like memchr are defined both in libc++ and libc. Including both would result in ambiguous references at the call sites. This is worked around by an attribute that tells the compiler to prefer one overload over the others. This attribute was not interpreted by Swift. As a result, importing both libc and libc++ and calling such functions resulted in compilation errors due to ambiguous overloads. This PR modifies the lookup logic to exclude the non-preferred Clang functions from the overload set whenever a preferred overload is available.
rdar://152192945