r321052 - [Coverage] Fix use-after free in coverage emission

[Eli Friedman via cfe-commits]

Author: efriedma
Date: Mon Dec 18 17:54:09 2017
New Revision: 321052

URL: http://llvm.org/viewvc/llvm-project?rev=321052&view=rev
Log:
[Coverage] Fix use-after free in coverage emission

Fixes regression from r320533.

This fixes the undefined behavior, but I'm not sure it's really right...
I think we end up with missing coverage for code in modules.

Differential Revision: https://reviews.llvm.org/D41374


Modified:
    cfe/trunk/lib/CodeGen/CodeGenModule.cpp

Modified: cfe/trunk/lib/CodeGen/CodeGenModule.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenModule.cpp?rev=321052&r1=321051&r2=321052&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenModule.cpp (original)
+++ cfe/trunk/lib/CodeGen/CodeGenModule.cpp Mon Dec 18 17:54:09 2017
@@ -4289,7 +4289,11 @@ void CodeGenModule::ClearUnusedCoverageM
 }
 
 void CodeGenModule::EmitDeferredUnusedCoverageMappings() {
-  for (const auto &Entry : DeferredEmptyCoverageMappingDecls) {
+  // We call takeVector() here to avoid use-after-free.
+  // FIXME: DeferredEmptyCoverageMappingDecls is getting mutated because
+  // we deserialize function bodies to emit coverage info for them, and that
+  // deserializes more declarations. How should we handle that case?
+  for (const auto &Entry : DeferredEmptyCoverageMappingDecls.takeVector()) {
     if (!Entry.second)
       continue;
     const Decl *D = Entry.first;