Step #1/N of implementing support for __label__: split labels into

LabelDecl and LabelStmt.  There is a 1-1 correspondence between the
two, but this simplifies a bunch of code by itself.  This is because
labels are the only place where we previously had references to random
other statements, causing grief for AST serialization and other stuff.

This does cause one regression (attr(unused) doesn't silence unused
label warnings) which I'll address next.

This does fix some minor bugs:
1. "The only valid attribute " diagnostic was capitalized.
2. Various diagnostics printed as ''labelname'' instead of 'labelname'
3. This reduces duplication of label checking between functions and blocks.

Review appreciated, particularly for the cindex and template bits.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@125733 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 48 insertions, 0 deletions

diff --git a/lib/Sema/Sema.cpp b/lib/Sema/Sema.cpp
index 8fbbeb85e3..2e7f72f81c 100644
--- a/lib/Sema/Sema.cpp
+++ b/lib/Sema/Sema.cpp
@@ -31,6 +31,7 @@
 #include "clang/AST/DeclCXX.h"
 #include "clang/AST/DeclObjC.h"
 #include "clang/AST/Expr.h"
+#include "clang/AST/StmtCXX.h"
 #include "clang/Lex/Preprocessor.h"
 #include "clang/Basic/PartialDiagnostic.h"
 #include "clang/Basic/TargetInfo.h"
@@ -50,6 +51,53 @@ void FunctionScopeInfo::Clear() {
   ErrorTrap.reset();
 }
 
+bool FunctionScopeInfo::checkLabelUse(Stmt *Body, Sema &S) {
+  bool AnyErrors = false;
+  for (llvm::DenseMap<IdentifierInfo*, LabelDecl*>::iterator
+       I = LabelMap.begin(), E = LabelMap.end(); I != E; ++I) {
+    LabelDecl *L = I->second;
+    
+    // Verify that we have no forward references left.  If so, there was a goto
+    // or address of a label taken, but no definition of it.  Label fwd
+    // definitions are indicated with a null substmt.
+    if (L->getStmt() != 0) {
+      if (!L->isUsed())
+        S.Diag(L->getLocation(), diag::warn_unused_label) << L->getDeclName();
+      continue;
+    }
+    
+    AnyErrors = true;
+    
+    // Emit error.
+    S.Diag(L->getLocation(), diag::err_undeclared_label_use) << L->getDeclName();
+    
+    // At this point, we have gotos that use the bogus label.  Stitch it into
+    // the function body so that the AST is well formed.
+    if (Body == 0) {
+      // The whole function wasn't parsed correctly.
+      continue;
+    }
+    
+    // Otherwise, the body is valid: we want to stitch the label decl into the
+    // function somewhere so that it is properly owned and so that the goto
+    // has a valid target.  Do this by creating LabelStmt and adding it to the
+    // end of the outer CompoundStmt.
+    LabelStmt *LS = new (S.Context) LabelStmt(L->getLocation(), L, 
+                                    new (S.Context) NullStmt(L->getLocation()));
+    
+    CompoundStmt *Compound = isa<CXXTryStmt>(Body) ?
+    cast<CXXTryStmt>(Body)->getTryBlock() :
+    cast<CompoundStmt>(Body);
+    llvm::SmallVector<Stmt*, 64> Elements(Compound->body_begin(),
+                                          Compound->body_end());
+    Elements.push_back(LS);
+    Compound->setStmts(S.Context, Elements.data(), Elements.size());
+  }
+  return AnyErrors;
+}
+
+
+
 BlockScopeInfo::~BlockScopeInfo() { }
 
 void Sema::ActOnTranslationUnitScope(Scope *S) {