[cfe-commits] r140138 - in /cfe/trunk: lib/Sema/SemaDeclCXX.cpp test/SemaCXX/return-noreturn.cpp

[Chandler Carruth]

Author: chandlerc
Date: Mon Sep 19 23:55:26 2011
New Revision: 140138

URL: http://llvm.org/viewvc/llvm-project?rev=140138&view=rev
Log:
Fix a pretty nasty bug in noreturn destructors that cascaded into lots
of false positive warnings that depend on noreturn destructors pruning
the CFGs, but only in C++0x mode!

This was really surprising as the debugger quickly reveals that the
attributes are parsed correctly (and using the same code) in both modes.
The warning fires in the same way in both modes. But between parsing and
building the destructor declaration with the noreturn attribute and the
warning, it magically disappears. The key? The 'noexcept' appears!

When we were rebuilding the destructor type with the computed implicit
noexcept we completely dropped the old type on the floor. This almost
makes sense (as the arguments and return type to a destructor aren't
exactly unpredictable), but lost any function type attributes as well.
The fix is simple, we build the new type off of the old one rather than
starting fresh.

Testing this is a bit awkward. I've done it by running the
noreturn-sensitive tests in both modes, which previous failed and now
passes, but if anyone has ideas about how to more specifically and
thoroughly test that the extended info on a destructor is preserved when
adding noexcept, I'm all ears.

Modified:
    cfe/trunk/lib/Sema/SemaDeclCXX.cpp
    cfe/trunk/test/SemaCXX/return-noreturn.cpp

Modified: cfe/trunk/lib/Sema/SemaDeclCXX.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclCXX.cpp?rev=140138&r1=140137&r2=140138&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaDeclCXX.cpp (original)
+++ cfe/trunk/lib/Sema/SemaDeclCXX.cpp Mon Sep 19 23:55:26 2011
@@ -6964,8 +6964,10 @@
   ImplicitExceptionSpecification exceptSpec =
       ComputeDefaultedDtorExceptionSpec(classDecl);
 
-  // Replace the destructor's type.
-  FunctionProtoType::ExtProtoInfo epi;
+  // Replace the destructor's type, building off the existing one. Fortunately,
+  // the only thing of interest in the destructor type is its extended info.
+  // The return and arguments are fixed.
+  FunctionProtoType::ExtProtoInfo epi = dtorType->getExtProtoInfo();
   epi.ExceptionSpecType = exceptSpec.getExceptionSpecType();
   epi.NumExceptions = exceptSpec.size();
   epi.Exceptions = exceptSpec.data();

Modified: cfe/trunk/test/SemaCXX/return-noreturn.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/return-noreturn.cpp?rev=140138&r1=140137&r2=140138&view=diff
==============================================================================
--- cfe/trunk/test/SemaCXX/return-noreturn.cpp (original)
+++ cfe/trunk/test/SemaCXX/return-noreturn.cpp Mon Sep 19 23:55:26 2011
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 %s -fsyntax-only -verify -Wreturn-type -Wmissing-noreturn -Wno-unreachable-code
+// RUN: %clang_cc1 %s -fsyntax-only -std=c++0x -verify -Wreturn-type -Wmissing-noreturn -Wno-unreachable-code
 
 // A destructor may be marked noreturn and should still influence the CFG.
 void pr6884_abort() __attribute__((noreturn));