Add the `pass_object_size` attribute to clang.

`pass_object_size` is our way of enabling `__builtin_object_size` to
produce high quality results without requiring inlining to happen
everywhere.

A link to the design doc for this attribute is available at the
Differential review link below.

Differential Revision: http://reviews.llvm.org/D13263

llvm-svn: 254554

1 files changed, 26 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index a6f2d5d6450..af5fdc95c90 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2621,6 +2621,21 @@ static bool checkUsingShadowRedecl(Sema &S, UsingShadowDecl *OldS,
   return false;
 }
 
+static bool hasIdenticalPassObjectSizeAttrs(const FunctionDecl *A,
+                                            const FunctionDecl *B) {
+  assert(A->getNumParams() == B->getNumParams());
+
+  auto AttrEq = [](const ParmVarDecl *A, const ParmVarDecl *B) {
+    const auto *AttrA = A->getAttr<PassObjectSizeAttr>();
+    const auto *AttrB = B->getAttr<PassObjectSizeAttr>();
+    if (AttrA == AttrB)
+      return true;
+    return AttrA && AttrB && AttrA->getType() == AttrB->getType();
+  };
+
+  return std::equal(A->param_begin(), A->param_end(), B->param_begin(), AttrEq);
+}
+
 /// MergeFunctionDecl - We just parsed a function 'New' from
 /// declarator D which has the same name and scope as a previous
 /// declaration 'Old'.  Figure out how to resolve this situation,
@@ -2799,7 +2814,17 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New, NamedDecl *&OldD,
       Old->isInlined() && !Old->hasAttr<GNUInlineAttr>()) {
     UndefinedButUsed.erase(Old->getCanonicalDecl());
   }
-  
+
+  // If pass_object_size params don't match up perfectly, this isn't a valid
+  // redeclaration.
+  if (Old->getNumParams() > 0 && Old->getNumParams() == New->getNumParams() &&
+      !hasIdenticalPassObjectSizeAttrs(Old, New)) {
+    Diag(New->getLocation(), diag::err_different_pass_object_size_params)
+        << New->getDeclName();
+    Diag(OldLocation, PrevDiag) << Old << Old->getType();
+    return true;
+  }
+
   if (getLangOpts().CPlusPlus) {
     // (C++98 13.1p2):
     //   Certain function declarations cannot be overloaded: