[PATCH] D41374: [Coverage] Fix use-after free in coverage emission

[Eli Friedman via Phabricator via cfe-commits]

efriedma created this revision.
efriedma added reviewers: vsk, davidxl.
efriedma added a project: clang.

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.


Repository:
  rC Clang

https://reviews.llvm.org/D41374

Files:
  lib/CodeGen/CodeGenModule.cpp


Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -4289,7 +4289,11 @@
 }
 
 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;



Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -4289,7 +4289,11 @@
 }
 
 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;

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