[clang] 0a14674 - CodeGen: Strip exception specifications from function types in CFI type names.

[Nico Weber via cfe-commits]

Author: Peter Collingbourne
Date: 2021-12-03T14:50:52-05:00
New Revision: 0a14674f276b598d23353290635fc62f93e9ab30

URL: https://github.com/llvm/llvm-project/commit/0a14674f276b598d23353290635fc62f93e9ab30
DIFF: https://github.com/llvm/llvm-project/commit/0a14674f276b598d23353290635fc62f93e9ab30.diff

LOG: CodeGen: Strip exception specifications from function types in CFI type names.

With C++17 the exception specification has been made part of the
function type, and therefore part of mangled type names.

However, it's valid to convert function pointers with an exception
specification to function pointers with the same argument and return
types but without an exception specification, which means that e.g. a
function of type "void () noexcept" can be called through a pointer
of type "void ()". We must therefore consider the two types to be
compatible for CFI purposes.

We can do this by stripping the exception specification before mangling
the type name, which is what this patch does.

Differential Revision: https://reviews.llvm.org/D115015

Added: 
    clang/test/CodeGenCXX/cfi-icall-noexcept.cpp

Modified: 
    clang/lib/CodeGen/CodeGenModule.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 9ba1a5c25e81a..39044617d6774 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -6398,6 +6398,11 @@ void CodeGenModule::EmitOMPThreadPrivateDecl(const OMPThreadPrivateDecl *D) {
 llvm::Metadata *
 CodeGenModule::CreateMetadataIdentifierImpl(QualType T, MetadataTypeMap &Map,
                                             StringRef Suffix) {
+  if (auto *FnType = T->getAs<FunctionProtoType>())
+    T = getContext().getFunctionType(
+        FnType->getReturnType(), FnType->getParamTypes(),
+        FnType->getExtProtoInfo().withExceptionSpec(EST_None));
+
   llvm::Metadata *&InternalId = Map[T.getCanonicalType()];
   if (InternalId)
     return InternalId;

diff  --git a/clang/test/CodeGenCXX/cfi-icall-noexcept.cpp b/clang/test/CodeGenCXX/cfi-icall-noexcept.cpp
new file mode 100644
index 0000000000000..eabc4862b4c52
--- /dev/null
+++ b/clang/test/CodeGenCXX/cfi-icall-noexcept.cpp
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -triple x86_64-unknown-linux -fsanitize=cfi-icall -emit-llvm -std=c++17 -o - %s | FileCheck %s
+
+// Tests that exception specifiers are stripped when forming the
+// mangled CFI type name.
+
+void f() noexcept {}
+
+// CHECK: define{{.*}} void @_Z1fv({{.*}} !type [[TS1:![0-9]+]] !type [[TS2:![0-9]+]]
+
+// CHECK: [[TS1]] = !{i64 0, !"_ZTSFvvE"}
+// CHECK: [[TS2]] = !{i64 0, !"_ZTSFvvE.generalized"}