Don't warn for empty 'if' body if there is a macro that expands to nothing, e.g:

  if (condition)
    CALL(0); // empty macro but don't warn for empty body.

Fixes rdar://8436021.

llvm-svn: 119838

2 files changed, 16 insertions, 8 deletions

diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index a4f1d34aec3..c6194edac3a 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -282,8 +282,8 @@ Sema::ActOnLabelStmt(SourceLocation IdentLoc, IdentifierInfo *II,
 
 StmtResult
 Sema::ActOnIfStmt(SourceLocation IfLoc, FullExprArg CondVal, Decl *CondVar,
-                  Stmt *thenStmt, SourceLocation ElseLoc,
-                  Stmt *elseStmt) {
+                  Stmt *thenStmt, bool MacroExpandedInThenStmt,
+                  SourceLocation ElseLoc, Stmt *elseStmt) {
   ExprResult CondResult(CondVal.release());
 
   VarDecl *ConditionVar = 0;
@@ -304,17 +304,23 @@ Sema::ActOnIfStmt(SourceLocation IfLoc, FullExprArg CondVal, Decl *CondVar,
   // if (condition);
   //   do_stuff();
   //
-  // NOTE: Do not emit this warning if the body is expanded from a macro.
   if (!elseStmt) {
     if (NullStmt* stmt = dyn_cast<NullStmt>(thenStmt))
-      if (!stmt->getLocStart().isMacroID())
+      // But do not warn if the body is a macro that expands to nothing, e.g:
+      //
+      // #define CALL(x)
+      // if (condition)
+      //   CALL(0);
+      //
+      if (!MacroExpandedInThenStmt)
         Diag(stmt->getSemiLoc(), diag::warn_empty_if_body);
   }
 
   DiagnoseUnusedExprResult(elseStmt);
 
   return Owned(new (Context) IfStmt(Context, IfLoc, ConditionVar, ConditionExpr, 
-                                    thenStmt, ElseLoc, elseStmt));
+                                    thenStmt, ElseLoc, elseStmt,
+                                    MacroExpandedInThenStmt));
 }
 
 /// ConvertIntegerToTypeWarnOnOverflow - Convert the specified APInt to have
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 807346c4c57..3ae4e5c5f49 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -772,9 +772,11 @@ public:
   /// By default, performs semantic analysis to build the new statement.
   /// Subclasses may override this routine to provide different behavior.
   StmtResult RebuildIfStmt(SourceLocation IfLoc, Sema::FullExprArg Cond,
-                                 VarDecl *CondVar, Stmt *Then, 
+                                 VarDecl *CondVar, Stmt *Then,
+                                 bool MacroExpandedInThenStmt,
                                  SourceLocation ElseLoc, Stmt *Else) {
-    return getSema().ActOnIfStmt(IfLoc, Cond, CondVar, Then, ElseLoc, Else);
+    return getSema().ActOnIfStmt(IfLoc, Cond, CondVar, Then,
+                                 MacroExpandedInThenStmt, ElseLoc, Else);
   }
 
   /// \brief Start building a new switch statement.
@@ -3692,7 +3694,7 @@ TreeTransform<Derived>::TransformIfStmt(IfStmt *S) {
     return SemaRef.Owned(S);
 
   return getDerived().RebuildIfStmt(S->getIfLoc(), FullCond, ConditionVar,
-                                    Then.get(),
+                                    Then.get(), S->hasMacroExpandedInThenStmt(),
                                     S->getElseLoc(), Else.get());
 }