[CodeGen][CXX]: Fix no_destroy CG bug under specific circumstances

Summary:

Class with no user-defined destructor that has an inherited member that has a
non-trivial destructor and a non-default constructor will attempt to emit a
destructor despite being marked as __attribute((no_destroy)) in which case it
would trigger an assertion due to an incorrect assumption. 

In addition this adds missing test coverage for IR generation for no_destroy.

(Note that here use of no_destroy is synonymous with its global flag 
counterpart `-fno-c++-static-destructors` being enabled)

Differential Revision: https://reviews.llvm.org/D54344

llvm-svn: 346628

1 files changed, 9 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGDeclCXX.cpp b/clang/lib/CodeGen/CGDeclCXX.cpp
index 4a025c27652..2884f138719 100644
--- a/clang/lib/CodeGen/CGDeclCXX.cpp
+++ b/clang/lib/CodeGen/CGDeclCXX.cpp
@@ -64,6 +64,15 @@ static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
 /// static storage duration.
 static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
                             ConstantAddress Addr) {
+  // Honor __attribute__((no_destroy)) and bail instead of attempting
+  // to emit a reference to a possibly nonexistent destructor, which
+  // in turn can cause a crash. This will result in a global constructor
+  // that isn't balanced out by a destructor call as intended by the
+  // attribute. This also checks for -fno-c++-static-destructors and
+  // bails even if the attribute is not present.
+  if (D.isNoDestroy(CGF.getContext()))
+    return;
+  
   CodeGenModule &CGM = CGF.CGM;
 
   // FIXME:  __attribute__((cleanup)) ?