[PATCH] D65913: Fix segfault caused by the "libstdc++ eager exception spec hack"

[Brad Moody via Phabricator via cfe-commits]

bmoody created this revision.
bmoody added a reviewer: rsmith.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Segfault occurs when the hack is applied to a function decl containing
an unparsed default argument. Parser::HandleMemberFunctionDeclDelays
was assuming that if a decl contains an unparsed default arg then it
must also have an unparsed exception spec. This causes a
read-from-wrong-union-member on FunctionTypeInfo::ExceptionSpecTokens,
triggering a segfault later on when the pointer is used.


Repository:
  rC Clang

https://reviews.llvm.org/D65913

Files:
  clang/lib/Parse/ParseDeclCXX.cpp
  clang/test/SemaCXX/libstdcxx_pair_swap_hack.cpp


Index: clang/test/SemaCXX/libstdcxx_pair_swap_hack.cpp
===================================================================
--- clang/test/SemaCXX/libstdcxx_pair_swap_hack.cpp
+++ clang/test/SemaCXX/libstdcxx_pair_swap_hack.cpp
@@ -9,6 +9,7 @@
 
 // RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=array
 // RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=array -DPR28423
+// RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=array -DDEFAULT_ARG
 // RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=pair
 // RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=priority_queue
 // RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify -fexceptions -fcxx-exceptions -DCLASS=stack
@@ -48,7 +49,11 @@
 #endif
     A member;
 #ifndef MSVC
+#ifndef DEFAULT_ARG
     void swap(CLASS &other) noexcept(noexcept(swap(member, other.member)));
+#else
+    void swap(CLASS &other, int = 0) noexcept(noexcept(swap(member, other.member)));
+#endif
 #endif
   };
 
Index: clang/lib/Parse/ParseDeclCXX.cpp
===================================================================
--- clang/lib/Parse/ParseDeclCXX.cpp
+++ clang/lib/Parse/ParseDeclCXX.cpp
@@ -2180,8 +2180,10 @@
     LateMethod->TemplateScope = getCurScope()->isTemplateParamScope();
 
     // Stash the exception-specification tokens in the late-pased method.
-    LateMethod->ExceptionSpecTokens = FTI.ExceptionSpecTokens;
-    FTI.ExceptionSpecTokens = nullptr;
+    if (FTI.getExceptionSpecType() == EST_Unparsed) {
+      LateMethod->ExceptionSpecTokens = FTI.ExceptionSpecTokens;
+      FTI.ExceptionSpecTokens = nullptr;
+    }
 
     // Push tokens for each parameter.  Those that do not have
     // defaults will be NULL.


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