[MS] Fix late-parsed template infinite loop in eager instantiation

Summary:
This fixes PR33561 and PR34185.

Don't store pending template instantiations for late-parsed templates in
the normal PendingInstantiations queue. Instead, use a separate list
that will only be parsed and instantiated at end of TU when late
template parsing actually works and doesn't infinite loop.

Reviewers: rsmith, thakis, hans

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D44846

llvm-svn: 328567

1 files changed, 19 insertions, 0 deletions

diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 171b3ec5f8a..5c0026cd374 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -850,6 +850,20 @@ void Sema::ActOnEndOfTranslationUnit() {
   if (PP.isCodeCompletionEnabled())
     return;
 
+  // Transfer late parsed template instantiations over to the pending template
+  // instantiation list. During normal compliation, the late template parser
+  // will be installed and instantiating these templates will succeed.
+  //
+  // If we are building a TU prefix for serialization, it is also safe to
+  // transfer these over, even though they are not parsed. The end of the TU
+  // should be outside of any eager template instantiation scope, so when this
+  // AST is deserialized, these templates will not be parsed until the end of
+  // the combined TU.
+  PendingInstantiations.insert(PendingInstantiations.end(),
+                               LateParsedInstantiations.begin(),
+                               LateParsedInstantiations.end());
+  LateParsedInstantiations.clear();
+
   // Complete translation units and modules define vtables and perform implicit
   // instantiations. PCH files do not.
   if (TUKind != TU_Prefix) {
@@ -879,8 +893,13 @@ void Sema::ActOnEndOfTranslationUnit() {
       PendingInstantiations.insert(PendingInstantiations.begin(),
                                    Pending.begin(), Pending.end());
     }
+
     PerformPendingInstantiations();
 
+    assert(LateParsedInstantiations.empty() &&
+           "end of TU template instantiation should not create more "
+           "late-parsed templates");
+
     if (LateTemplateParserCleanup)
       LateTemplateParserCleanup(OpaqueParser);