Re-land "[Sema] Make getCurFunction() return null outside function parsing"

This relands r326965.

There was a null dereference in typo correction that was triggered in
Sema/diagnose_if.c. We are not always in a function scope when doing
typo correction. The fix is to add a null check.

LLVM's optimizer made it hard to find this bug. I wrote it up in a
not-very-well-editted blog post here:
http://qinsb.blogspot.com/2018/03/ub-will-delete-your-null-checks.html

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@327334 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 8 deletions

diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 08af3fa676..918dc92f2b 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -557,7 +557,7 @@ StmtResult Sema::BuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
     return StmtError();
 
   if (IsConstexpr || isa<ObjCAvailabilityCheckExpr>(Cond.get().second))
-    getCurFunction()->setHasBranchProtectedScope();
+    setFunctionHasBranchProtectedScope();
 
   DiagnoseUnusedExprResult(thenStmt);
   DiagnoseUnusedExprResult(elseStmt);
@@ -688,7 +688,7 @@ StmtResult Sema::ActOnStartOfSwitchStmt(SourceLocation SwitchLoc,
   if (Cond.isInvalid())
     return StmtError();
 
-  getCurFunction()->setHasBranchIntoScope();
+  setFunctionHasBranchIntoScope();
 
   SwitchStmt *SS = new (Context)
       SwitchStmt(Context, InitStmt, Cond.get().first, Cond.get().second);
@@ -1873,7 +1873,7 @@ StmtResult
 Sema::ActOnObjCForCollectionStmt(SourceLocation ForLoc,
                                  Stmt *First, Expr *collection,
                                  SourceLocation RParenLoc) {
-  getCurFunction()->setHasBranchProtectedScope();
+  setFunctionHasBranchProtectedScope();
 
   ExprResult CollectionExprResult =
     CheckObjCForCollectionOperand(ForLoc, collection);
@@ -2784,7 +2784,7 @@ StmtResult Sema::FinishCXXForRangeStmt(Stmt *S, Stmt *B) {
 StmtResult Sema::ActOnGotoStmt(SourceLocation GotoLoc,
                                SourceLocation LabelLoc,
                                LabelDecl *TheDecl) {
-  getCurFunction()->setHasBranchIntoScope();
+  setFunctionHasBranchIntoScope();
   TheDecl->markUsed(Context);
   return new (Context) GotoStmt(TheDecl, GotoLoc, LabelLoc);
 }
@@ -2811,7 +2811,7 @@ Sema::ActOnIndirectGotoStmt(SourceLocation GotoLoc, SourceLocation StarLoc,
     return StmtError();
   E = ExprRes.get();
 
-  getCurFunction()->setHasIndirectGoto();
+  setFunctionHasIndirectGoto();
 
   return new (Context) IndirectGotoStmt(GotoLoc, StarLoc, E);
 }
@@ -3607,7 +3607,7 @@ Sema::ActOnObjCAtTryStmt(SourceLocation AtLoc, Stmt *Try,
   if (!getLangOpts().ObjCExceptions)
     Diag(AtLoc, diag::err_objc_exceptions_disabled) << "@try";
 
-  getCurFunction()->setHasBranchProtectedScope();
+  setFunctionHasBranchProtectedScope();
   unsigned NumCatchStmts = CatchStmts.size();
   return ObjCAtTryStmt::Create(Context, AtLoc, Try, CatchStmts.data(),
                                NumCatchStmts, Finally);
@@ -3698,7 +3698,7 @@ StmtResult
 Sema::ActOnObjCAtSynchronizedStmt(SourceLocation AtLoc, Expr *SyncExpr,
                                   Stmt *SyncBody) {
   // We can't jump into or indirect-jump out of a @synchronized block.
-  getCurFunction()->setHasBranchProtectedScope();
+  setFunctionHasBranchProtectedScope();
   return new (Context) ObjCAtSynchronizedStmt(AtLoc, SyncExpr, SyncBody);
 }
 
@@ -3714,7 +3714,7 @@ Sema::ActOnCXXCatchBlock(SourceLocation CatchLoc, Decl *ExDecl,
 
 StmtResult
 Sema::ActOnObjCAutoreleasePoolStmt(SourceLocation AtLoc, Stmt *Body) {
-  getCurFunction()->setHasBranchProtectedScope();
+  setFunctionHasBranchProtectedScope();
   return new (Context) ObjCAutoreleasePoolStmt(AtLoc, Body);
 }