"floating point arithmetic produces %select{an infinity|a NaN}0">;
def note_constexpr_pointer_subtraction_not_same_array : Note<
"subtracted pointers are not elements of the same array">;
+def note_constexpr_pointer_subtraction_zero_size : Note<
+ "subtraction of pointers to type %0 of zero size">;
def note_constexpr_pointer_comparison_base_classes : Note<
"comparison of addresses of subobjects of different base classes "
"has unspecified value">;
def warn_offsetof_non_standardlayout_type : ExtWarn<
"offset of on non-standard-layout type %0">, InGroup<InvalidOffsetof>;
def err_offsetof_bitfield : Error<"cannot compute offset of bit-field %0">;
+def warn_sub_ptr_zero_size_types : Warning<
+ "subtraction of pointers to type %0 of zero size has undefined behavior">,
+ InGroup<PointerArith>;
def warn_floatingpoint_eq : Warning<
"comparing floating point with == or != is unsafe">,
if (!HandleSizeof(Info, E->getExprLoc(), ElementType, ElementSize))
return false;
+ // As an extension, a type may have zero size (empty struct or union in
+ // C, array of zero length). Pointer subtraction in such cases has
+ // undefined behavior, so is not constant.
+ if (ElementSize.isZero()) {
+ Info.Diag(E, diag::note_constexpr_pointer_subtraction_zero_size)
+ << ElementType;
+ return false;
+ }
+
// FIXME: LLVM and GCC both compute LHSOffset - RHSOffset at runtime,
// and produce incorrect results when it overflows. Such behavior
// appears to be non-conforming, but is common, so perhaps we should
LHS.get(), RHS.get()))
return QualType();
+ // The pointee type may have zero size. As an extension, a structure or
+ // union may have zero size or an array may have zero length. In this
+ // case subtraction does not make sense.
+ if (!rpointee->isVoidType() && !rpointee->isFunctionType()) {
+ CharUnits ElementSize = Context.getTypeSizeInChars(rpointee);
+ if (ElementSize.isZero()) {
+ Diag(Loc,diag::warn_sub_ptr_zero_size_types)
+ << rpointee.getUnqualifiedType()
+ << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
+ }
+ }
+
if (CompLHSTy) *CompLHSTy = LHS.get()->getType();
return Context.getPointerDiffType();
}
struct emp_1 f1;
union emp_2 f2;
};
+
+// Checks for pointer subtraction (PR15683)
+struct emp_1 *func_1p(struct emp_1 *x) { return x - 5; }
+
+int func_1() {
+ struct emp_1 v[1];
+ return v - v; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}}
+}
+
+int func_2(struct emp_1 *x) {
+ return 1 + x - x; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}}
+}
+
+int func_3(struct emp_1 *x, struct emp_1 *y) {
+ return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}}
+}
+
+int func_4(struct emp_1 *x, const struct emp_1 *y) {
+ return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}}
+}
+
+int func_5(volatile struct emp_1 *x, const struct emp_1 *y) {
+ return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}}
+}
+
+int func_6() {
+ union emp_2 v[1];
+ return v - v; // expected-warning {{subtraction of pointers to type 'union emp_2' of zero size has undefined behavior}}
+}
+
+struct A; // expected-note {{forward declaration of 'struct A'}}
+
+int func_7(struct A *x, struct A *y) {
+ return x - y; // expected-error {{arithmetic on a pointer to an incomplete type 'struct A'}}
+}
+
+int func_8(struct emp_1 (*x)[10], struct emp_1 (*y)[10]) {
+ return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1 [10]' of zero size has undefined behavior}}
+}
+
+int func_9(struct emp_1 (*x)[], struct emp_1 (*y)[]) {
+ return x - y; // expected-error {{arithmetic on a pointer to an incomplete type 'struct emp_1 []'}}
+}
+
+int func_10(int (*x)[0], int (*y)[0]) {
+ return x - y; // expected-warning {{subtraction of pointers to type 'int [0]' of zero size has undefined behavior}}
+}
-// RUN: %clang_cc1 -triple i686-linux -Wno-string-plus-int -fsyntax-only -fcxx-exceptions -verify -std=c++11 -pedantic %s -Wno-comment
+// RUN: %clang_cc1 -triple i686-linux -Wno-string-plus-int -Wno-pointer-arith -Wno-zero-length-array -fsyntax-only -fcxx-exceptions -verify -std=c++11 -pedantic %s -Wno-comment
namespace StaticAssertFoldTest {
static_assert(X::f(3) == -1, "3 should truncate to -1");
}
}
+
+namespace ZeroSizeTypes {
+ constexpr int (*p1)[0] = 0, (*p2)[0] = 0;
+ constexpr int k = p2 - p1;
+ // expected-error@-1 {{constexpr variable 'k' must be initialized by a constant expression}}
+ // expected-note@-2 {{subtraction of pointers to type 'int [0]' of zero size}}
+
+ int arr[5][0];
+ constexpr int f() { // expected-error {{never produces a constant expression}}
+ return &arr[3] - &arr[0]; // expected-note {{subtraction of pointers to type 'int [0]' of zero size}}
+ }
+}