__builtin_object_size refinements. When we run out of object, be sure

to clamp at 0 bytes left.  WIP.

llvm-svn: 85157

2 files changed, 24 insertions, 4 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index f1a446ef6e7..9992b6944ec 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -884,7 +884,11 @@ bool IntExprEvaluator::VisitCallExpr(const CallExpr *E) {
         if (const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(LVBase)) {
           if (const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl())) {
             uint64_t Size = Info.Ctx.getTypeSize(VD->getType()) / 8;
-            Size -= Base.Val.getLValueOffset();
+            uint64_t Offset = Base.Val.getLValueOffset();
+            if (Offset <= Size)
+              Size -= Base.Val.getLValueOffset();
+            else
+              Size = 0;
             return Success(Size, E);
           }
         }
diff --git a/clang/test/CodeGen/object-size.c b/clang/test/CodeGen/object-size.c
index b6861169893..36dc341e932 100644
--- a/clang/test/CodeGen/object-size.c
+++ b/clang/test/CodeGen/object-size.c
@@ -21,13 +21,29 @@ void test2() {
   strcpy(gbuf, "Hi there");
 }
 
+void test3() {
+  // CHECK:       movabsq $0, %rdx
+  // CHECK-NEXT:  movq    %rax, %rdi
+  // CHECK-NEXT:  movq    %rcx, %rsi
+  // CHECK-NEXT:  call    ___strcpy_chk
+  strcpy(&gbuf[100], "Hi there");
+}
+
 void test4() {
+  // CHECK:       movabsq $0, %rdx
+  // CHECK-NEXT:  movq    %rax, %rdi
+  // CHECK-NEXT:  movq    %rcx, %rsi
+  // CHECK-NEXT:  call    ___strcpy_chk
+  strcpy((char*)(void*)&gbuf[-1], "Hi there");
+}
+
+void test5() {
   // CHECK:       call    ___inline_strcpy_chk
-  strcpy(gp, "Hi");
+  strcpy(gp, "Hi there");
 }
 
-void test3() {
+void test6() {
   int i;
   // CHECK:       call    ___inline_strcpy_chk
-  strcpy((++i, gbuf), "Hi");
+  strcpy((++i, gbuf), "Hi there");
 }