[Sema] Make getCurFunction() return null outside function parsing

Summary:
Before this patch, Sema pre-allocated a FunctionScopeInfo and kept it in
the first, always present element of the FunctionScopes stack. This
meant that Sema::getCurFunction would return a pointer to this
pre-allocated object when parsing code outside a function body. This is
pretty much always a bug, so this patch moves the pre-allocated object
into a separate unique_ptr. This should make bugs like PR36536 a lot
more obvious.

As you can see from this patch, there were a number of places that
unconditionally assumed they were always called inside a function.
However, there are also many places that null checked the result of
getCurFunction(), so I think this is a reasonable direction.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D44039

llvm-svn: 326965

1 files changed, 8 insertions, 10 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index d3ab003a339..4baf52f5b78 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1114,8 +1114,9 @@ bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
 
   assert((!ByCopy || Explicit) && "cannot implicitly capture *this by value");
 
-  const unsigned MaxFunctionScopesIndex = FunctionScopeIndexToStopAt ?
-    *FunctionScopeIndexToStopAt : FunctionScopes.size() - 1;
+  const int MaxFunctionScopesIndex = FunctionScopeIndexToStopAt
+                                         ? *FunctionScopeIndexToStopAt
+                                         : FunctionScopes.size() - 1;
 
   // Check that we can capture the *enclosing object* (referred to by '*this')
   // by the capturing-entity/closure (lambda/block/etc) at
@@ -1141,7 +1142,7 @@ bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
 
 
   unsigned NumCapturingClosures = 0;
-  for (unsigned idx = MaxFunctionScopesIndex; idx != 0; idx--) {
+  for (int idx = MaxFunctionScopesIndex; idx >= 0; idx--) {
     if (CapturingScopeInfo *CSI =
             dyn_cast<CapturingScopeInfo>(FunctionScopes[idx])) {
       if (CSI->CXXThisCaptureIndex != 0) {
@@ -1196,8 +1197,8 @@ bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
   // FIXME: We need to delay this marking in PotentiallyPotentiallyEvaluated
   // contexts.
   QualType ThisTy = getCurrentThisType();
-  for (unsigned idx = MaxFunctionScopesIndex; NumCapturingClosures;
-      --idx, --NumCapturingClosures) {
+  for (int idx = MaxFunctionScopesIndex; NumCapturingClosures;
+       --idx, --NumCapturingClosures) {
     CapturingScopeInfo *CSI = cast<CapturingScopeInfo>(FunctionScopes[idx]);
     Expr *ThisExpr = nullptr;
 
@@ -7176,9 +7177,6 @@ static void CheckIfAnyEnclosingLambdasMustCaptureAnyPotentialCaptures(
 
   const bool IsFullExprInstantiationDependent = FE->isInstantiationDependent();
 
-  ArrayRef<const FunctionScopeInfo *> FunctionScopesArrayRef(
-      S.FunctionScopes.data(), S.FunctionScopes.size());
-
   // All the potentially captureable variables in the current nested
   // lambda (within a generic outer lambda), must be captured by an
   // outer lambda that is enclosed within a non-dependent context.
@@ -7207,7 +7205,7 @@ static void CheckIfAnyEnclosingLambdasMustCaptureAnyPotentialCaptures(
     // capture the variable in that lambda (and all its enclosing lambdas).
     if (const Optional<unsigned> Index =
             getStackIndexOfNearestEnclosingCaptureCapableLambda(
-                FunctionScopesArrayRef, Var, S)) {
+                S.FunctionScopes, Var, S)) {
       const unsigned FunctionScopeIndexOfCapturableLambda = Index.getValue();
       MarkVarDeclODRUsed(Var, VarExpr->getExprLoc(), S,
                          &FunctionScopeIndexOfCapturableLambda);
@@ -7243,7 +7241,7 @@ static void CheckIfAnyEnclosingLambdasMustCaptureAnyPotentialCaptures(
     // 'this' in that lambda (and all its enclosing lambdas).
     if (const Optional<unsigned> Index =
             getStackIndexOfNearestEnclosingCaptureCapableLambda(
-                FunctionScopesArrayRef, /*0 is 'this'*/ nullptr, S)) {
+                S.FunctionScopes, /*0 is 'this'*/ nullptr, S)) {
       const unsigned FunctionScopeIndexOfCapturableLambda = Index.getValue();
       S.CheckCXXThisCapture(CurrentLSI->PotentialThisCaptureLocation,
                             /*Explicit*/ false, /*BuildAndDiagnose*/ true,