Fix a rejects-valid in C++11: array new of a negative size, or overflowing array

new, is well-formed with defined semantics of throwing (a type which can be
caught by a handler for) std::bad_array_new_length, unlike in C++98 where it is
somewhere nebulous between undefined behavior and ill-formed.

If the array size is an integral constant expression and satisfies one of these
criteria, we would previous the array new expression, but now in C++11 mode, we
merely issue a warning (the code is still rejected in C++98 mode, naturally).

We don't yet implement new C++11 semantics correctly (see PR11644), but we do
implement the overflow checking, and (for the default operator new) convert such
expressions to an exception, so accepting such code now does not seem especially
unsafe.

llvm-svn: 149767

4 files changed, 49 insertions, 17 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index f0f0a054d34..8f5e2c7e6b3 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2898,6 +2898,9 @@ def err_vm_func_decl : Error<
   "function declaration cannot have variably modified type">;
 def err_array_too_large : Error<
   "array is too large (%0 elements)">;
+def warn_array_new_too_large : Warning<"array is too large (%0 elements)">,
+  // FIXME PR11644: ", will throw std::bad_array_new_length at runtime"
+  InGroup<DiagGroup<"bad-array-new-length">>;
 
 // -Wpadded, -Wpacked
 def warn_padded_struct_field : Warning<
@@ -2913,6 +2916,9 @@ def warn_unnecessary_packed : Warning<
   "packed attribute is unnecessary for %0">, InGroup<Packed>, DefaultIgnore;
 
 def err_typecheck_negative_array_size : Error<"array size is negative">;
+def warn_typecheck_negative_array_new_size : Warning<"array size is negative">,
+  // FIXME PR11644: ", will throw std::bad_array_new_length at runtime"
+  InGroup<DiagGroup<"bad-array-new-length">>;
 def warn_typecheck_function_qualifiers : Warning<
   "qualifier on function type %0 has unspecified behavior">;
 def err_typecheck_invalid_restrict_not_pointer : Error<
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 793b70789a9..a0fb6e44d9c 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1018,28 +1018,44 @@ Sema::BuildCXXNew(SourceLocation StartLoc, bool UseGlobal,
     if (!SizeType->isIntegralOrUnscopedEnumerationType())
       return ExprError();
 
-    // Let's see if this is a constant < 0. If so, we reject it out of hand.
-    // We don't care about special rules, so we tell the machinery it's not
-    // evaluated - it gives us a result in more cases.
+    // C++98 [expr.new]p7:
+    //   The expression in a direct-new-declarator shall have integral type
+    //   with a non-negative value.
+    //
+    // Let's see if this is a constant < 0. If so, we reject it out of
+    // hand. Otherwise, if it's not a constant, we must have an unparenthesized
+    // array type.
+    //
+    // Note: such a construct has well-defined semantics in C++11: it throws
+    // std::bad_array_new_length.
     if (!ArraySize->isValueDependent()) {
       llvm::APSInt Value;
-      if (ArraySize->isIntegerConstantExpr(Value, Context, 0, false)) {
+      if (ArraySize->isIntegerConstantExpr(Value, Context)) {
         if (Value < llvm::APSInt(
                         llvm::APInt::getNullValue(Value.getBitWidth()),
-                                 Value.isUnsigned()))
-          return ExprError(Diag(ArraySize->getSourceRange().getBegin(),
-                                diag::err_typecheck_negative_array_size)
-            << ArraySize->getSourceRange());
-
-        if (!AllocType->isDependentType()) {
-          unsigned ActiveSizeBits
-            = ConstantArrayType::getNumAddressingBits(Context, AllocType, Value);
-          if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context)) {
+                                 Value.isUnsigned())) {
+          if (getLangOptions().CPlusPlus0x)
             Diag(ArraySize->getSourceRange().getBegin(),
-                 diag::err_array_too_large)
-              << Value.toString(10)
+                 diag::warn_typecheck_negative_array_new_size)
               << ArraySize->getSourceRange();
-            return ExprError();
+          else
+            return ExprError(Diag(ArraySize->getSourceRange().getBegin(),
+                                  diag::err_typecheck_negative_array_size)
+                             << ArraySize->getSourceRange());
+        } else if (!AllocType->isDependentType()) {
+          unsigned ActiveSizeBits =
+            ConstantArrayType::getNumAddressingBits(Context, AllocType, Value);
+          if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context)) {
+            if (getLangOptions().CPlusPlus0x)
+              Diag(ArraySize->getSourceRange().getBegin(),
+                   diag::warn_array_new_too_large)
+                << Value.toString(10)
+                << ArraySize->getSourceRange();
+            else
+              return ExprError(Diag(ArraySize->getSourceRange().getBegin(),
+                                    diag::err_array_too_large)
+                               << Value.toString(10)
+                               << ArraySize->getSourceRange());
           }
         }
       } else if (TypeIdParens.isValid()) {
diff --git a/clang/test/SemaCXX/new-delete-cxx0x.cpp b/clang/test/SemaCXX/new-delete-cxx0x.cpp
new file mode 100644
index 00000000000..87780ad6b8d
--- /dev/null
+++ b/clang/test/SemaCXX/new-delete-cxx0x.cpp
@@ -0,0 +1,9 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s -std=c++11 -triple=i686-pc-linux-gnu
+
+void ugly_news(int *ip) {
+  // These are ill-formed according to one reading of C++98, and at the least
+  // have undefined behavior. But they're well-formed, and defined to throw
+  // std::bad_array_new_length, in C++11.
+  (void)new int[-1]; // expected-warning {{array size is negative}}
+  (void)new int[2000000000]; // expected-warning {{array is too large}}
+}
diff --git a/clang/test/SemaCXX/new-delete.cpp b/clang/test/SemaCXX/new-delete.cpp
index 748ce777009..9cc290cbd71 100644
--- a/clang/test/SemaCXX/new-delete.cpp
+++ b/clang/test/SemaCXX/new-delete.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify %s -triple=i686-pc-linux-gnu
 
 #include <stddef.h>
 
@@ -77,6 +77,7 @@ void bad_news(int *ip)
   (void)new float*(ip); // expected-error {{cannot initialize a new value of type 'float *' with an lvalue of type 'int *'}}
   // Undefined, but clang should reject it directly.
   (void)new int[-1]; // expected-error {{array size is negative}}
+  (void)new int[2000000000]; // expected-error {{array is too large}}
   (void)new int[*(S*)0]; // expected-error {{array size expression must have integral or enumerated type, not 'S'}}
   (void)::S::new int; // expected-error {{expected unqualified-id}}
   (void)new (0, 0) int; // expected-error {{no matching function for call to 'operator new'}}