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
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index 3f81be0..3a46bbf 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4479,8 +4479,7 @@
CalleeType = getContext().getCanonicalType(CalleeType);
- const auto *FnType =
- cast<FunctionType>(cast<PointerType>(CalleeType)->getPointeeType());
+ auto PointeeType = cast<PointerType>(CalleeType)->getPointeeType();
CGCallee Callee = OrigCallee;
@@ -4489,8 +4488,12 @@
if (llvm::Constant *PrefixSig =
CGM.getTargetCodeGenInfo().getUBSanFunctionSignature(CGM)) {
SanitizerScope SanScope(this);
+ // Remove any (C++17) exception specifications, to allow calling e.g. a
+ // noexcept function through a non-noexcept pointer.
+ auto ProtoTy =
+ getContext().getFunctionTypeWithExceptionSpec(PointeeType, EST_None);
llvm::Constant *FTRTTIConst =
- CGM.GetAddrOfRTTIDescriptor(QualType(FnType, 0), /*ForEH=*/true);
+ CGM.GetAddrOfRTTIDescriptor(ProtoTy, /*ForEH=*/true);
llvm::Type *PrefixStructTyElems[] = {PrefixSig->getType(), Int32Ty};
llvm::StructType *PrefixStructTy = llvm::StructType::get(
CGM.getLLVMContext(), PrefixStructTyElems, /*isPacked=*/true);
@@ -4530,6 +4533,8 @@
}
}
+ const auto *FnType = cast<FunctionType>(PointeeType);
+
// If we are checking indirect calls and this call is indirect, check that the
// function pointer is a member of the bit set for the function type.
if (SanOpts.has(SanitizerKind::CFIICall) &&
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 664b510..6fb21b1 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -924,8 +924,13 @@
if (getLangOpts().CPlusPlus && SanOpts.has(SanitizerKind::Function)) {
if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D)) {
if (llvm::Constant *PrologueSig = getPrologueSignature(CGM, FD)) {
+ // Remove any (C++17) exception specifications, to allow calling e.g. a
+ // noexcept function through a non-noexcept pointer.
+ auto ProtoTy =
+ getContext().getFunctionTypeWithExceptionSpec(FD->getType(),
+ EST_None);
llvm::Constant *FTRTTIConst =
- CGM.GetAddrOfRTTIDescriptor(FD->getType(), /*ForEH=*/true);
+ CGM.GetAddrOfRTTIDescriptor(ProtoTy, /*ForEH=*/true);
llvm::Constant *FTRTTIConstEncoded =
EncodeAddrForUseInPrologue(Fn, FTRTTIConst);
llvm::Constant *PrologueStructElems[] = {PrologueSig,
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index c375b82..d2538e9 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -3435,9 +3435,7 @@
if (auto *Proto = Type->getAs<FunctionProtoType>()) {
if (Proto->isNothrow(Ctx)) {
Flags |= ItaniumRTTIBuilder::PTI_Noexcept;
- Type = Ctx.getFunctionType(
- Proto->getReturnType(), Proto->getParamTypes(),
- Proto->getExtProtoInfo().withExceptionSpec(EST_None));
+ Type = Ctx.getFunctionTypeWithExceptionSpec(Type, EST_None);
}
}