No -fsanitize=function warning when calling noexcept function through non-noexcept pointer in C++17

As discussed in the mail thread <https://groups.google.com/a/isocpp.org/forum/
#!topic/std-discussion/T64_dW3WKUk> "Calling noexcept function throug non-
noexcept pointer is undefined behavior?", such a call should not be UB.
However, Clang currently warns about it.

This change removes exception specifications from the function types recorded
for -fsanitize=function, both in the functions themselves and at the call sites.
That means that calling a non-noexcept function through a noexcept pointer will
also not be flagged as UB.  In the review of this change, that was deemed
acceptable, at least for now.  (See the "TODO" in compiler-rt
test/ubsan/TestCases/TypeCheck/Function/function.cpp.)

To remove exception specifications from types, the existing internal
ASTContext::getFunctionTypeWithExceptionSpec was made public, and some places
otherwise unrelated to this change have been adapted to call it, too.

This is the cfe part of a patch covering both cfe and compiler-rt.

Differential Revision: https://reviews.llvm.org/D40720

llvm-svn: 321859

1 files changed, 2 insertions, 4 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index f2b1963df1e..05434903221 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -1475,10 +1475,8 @@ bool Sema::IsFunctionConversion(QualType FromType, QualType ToType,
     const auto *ToFPT = cast<FunctionProtoType>(ToFn);
     if (FromFPT->isNothrow(Context) && !ToFPT->isNothrow(Context)) {
       FromFn = cast<FunctionType>(
-          Context.getFunctionType(FromFPT->getReturnType(),
-                                  FromFPT->getParamTypes(),
-                                  FromFPT->getExtProtoInfo().withExceptionSpec(
-                                      FunctionProtoType::ExceptionSpecInfo()))
+          Context.getFunctionTypeWithExceptionSpec(QualType(FromFPT, 0),
+                                                   EST_None)
                  .getTypePtr());
       Changed = true;
     }