[clang] fddc4e4 - Correct handling of the 'throw()' exception specifier in C++17.

[James Y Knight via cfe-commits]

Author: James Y Knight
Date: 2021-11-10T17:40:16-05:00
New Revision: fddc4e41164e2fd152605362639eb3255cc75212

URL: https://github.com/llvm/llvm-project/commit/fddc4e41164e2fd152605362639eb3255cc75212
DIFF: https://github.com/llvm/llvm-project/commit/fddc4e41164e2fd152605362639eb3255cc75212.diff

LOG: Correct handling of the 'throw()' exception specifier in C++17.

Per C++17 [except.spec], 'throw()' has become equivalent to
'noexcept', and should therefore call std::terminate, not
std::unexpected.

Differential Revision: https://reviews.llvm.org/D113517

Added: 
    

Modified: 
    clang/lib/CodeGen/CGException.cpp
    clang/test/CXX/except/except.spec/p9-dynamic.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CGException.cpp b/clang/lib/CodeGen/CGException.cpp
index 9f65e9eb120cf..aff9c77d53c78 100644
--- a/clang/lib/CodeGen/CGException.cpp
+++ b/clang/lib/CodeGen/CGException.cpp
@@ -477,11 +477,11 @@ void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
     return;
 
   ExceptionSpecificationType EST = Proto->getExceptionSpecType();
-  if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot) {
-    // noexcept functions are simple terminate scopes.
-    if (!getLangOpts().EHAsynch) // -EHa: HW exception still can occur
-      EHStack.pushTerminate();
-  } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
+  // In C++17 and later, 'throw()' aka EST_DynamicNone is treated the same way
+  // as noexcept. In earlier standards, it is handled in this block, along with
+  // 'throw(X...)'.
+  if (EST == EST_Dynamic ||
+      (EST == EST_DynamicNone && !getLangOpts().CPlusPlus17)) {
     // TODO: Revisit exception specifications for the MS ABI.  There is a way to
     // encode these in an object file but MSVC doesn't do anything with it.
     if (getTarget().getCXXABI().isMicrosoft())
@@ -521,6 +521,10 @@ void CodeGenFunction::EmitStartEHSpec(const Decl *D) {
                                                         /*ForEH=*/true);
       Filter->setFilter(I, EHType);
     }
+  } else if (Proto->canThrow() == CT_Cannot) {
+    // noexcept functions are simple terminate scopes.
+    if (!getLangOpts().EHAsynch) // -EHa: HW exception still can occur
+      EHStack.pushTerminate();
   }
 }
 
@@ -580,10 +584,8 @@ void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
     return;
 
   ExceptionSpecificationType EST = Proto->getExceptionSpecType();
-  if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot &&
-      !EHStack.empty() /* possible empty when under async exceptions */) {
-    EHStack.popTerminate();
-  } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
+  if (EST == EST_Dynamic ||
+      (EST == EST_DynamicNone && !getLangOpts().CPlusPlus17)) {
     // TODO: Revisit exception specifications for the MS ABI.  There is a way to
     // encode these in an object file but MSVC doesn't do anything with it.
     if (getTarget().getCXXABI().isMicrosoft())
@@ -599,6 +601,10 @@ void CodeGenFunction::EmitEndEHSpec(const Decl *D) {
     EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
     emitFilterDispatchBlock(*this, filterScope);
     EHStack.popFilter();
+  } else if (Proto->canThrow() == CT_Cannot &&
+              /* possible empty when under async exceptions */
+             !EHStack.empty()) {
+    EHStack.popTerminate();
   }
 }
 

diff  --git a/clang/test/CXX/except/except.spec/p9-dynamic.cpp b/clang/test/CXX/except/except.spec/p9-dynamic.cpp
index 1e7b29479fbdb..ccba71767729e 100644
--- a/clang/test/CXX/except/except.spec/p9-dynamic.cpp
+++ b/clang/test/CXX/except/except.spec/p9-dynamic.cpp
@@ -1,12 +1,26 @@
-// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - -fcxx-exceptions -fexceptions | FileCheck %s
+// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -emit-llvm -o - -fcxx-exceptions -fexceptions | FileCheck %s --check-prefixes=CHECK,CHECK-PRE17
+// RUN: %clang_cc1 %s -triple=x86_64-apple-darwin10 -std=c++17 -Wno-dynamic-exception-spec -emit-llvm -o - -fcxx-exceptions -fexceptions | FileCheck %s --check-prefixes=CHECK,CHECK-17
 
 void external();
 
+// CHECK-LABEL: _Z6targetv(
+// CHECK: invoke void @_Z8externalv()
+// CHECK:      landingpad { i8*, i32 }
+// CHECK-NEXT:   filter [1 x i8*] [i8* bitcast (i8** @_ZTIi to i8*)]
+// CHECK:      call void @__cxa_call_unexpected
 void target() throw(int)
 {
-  // CHECK: invoke void @_Z8externalv()
   external();
 }
-// CHECK:      landingpad { i8*, i32 }
-// CHECK-NEXT:   filter [1 x i8*] [i8* bitcast (i8** @_ZTIi to i8*)]
-// CHECK:      call void @__cxa_call_unexpected
+
+// CHECK-LABEL: _Z7target2v(
+// CHECK: invoke void @_Z8externalv()
+// CHECK:            landingpad { i8*, i32 }
+// CHECK-PRE17-NEXT:   filter [0 x i8*] zeroinitializer
+// CHECK-17-NEXT:      catch i8* null
+// CHECK-PRE17:      call void @__cxa_call_unexpected
+// CHECK-17:         call void @__clang_call_terminate
+void target2() throw()
+{
+  external();
+}