1 // RUN: %clang_cc1 %s -fsyntax-only -verify -Wc++-compat 2 3 struct emp_1 { // expected-warning {{empty struct has size 0 in C, size 1 in C++}} 4 }; 5 6 union emp_2 { // expected-warning {{empty union has size 0 in C, size 1 in C++}} 7 }; 8 9 struct emp_3 { // expected-warning {{struct has size 0 in C, size 1 in C++}} 10 int : 0; 11 }; 12 13 union emp_4 { // expected-warning {{union has size 0 in C, size 1 in C++}} 14 int : 0; 15 }; 16 17 struct emp_5 { // expected-warning {{struct has size 0 in C, size 1 in C++}} 18 int : 0; 19 int : 0; 20 }; 21 22 union emp_6 { // expected-warning {{union has size 0 in C, size 1 in C++}} 23 int : 0; 24 int : 0; 25 }; 26 27 struct emp_7 { // expected-warning {{struct has size 0 in C, size 1 in C++}} 28 struct emp_1 f1; 29 }; 30 31 union emp_8 { // expected-warning {{union has size 0 in C, size 1 in C++}} 32 struct emp_1 f1; 33 }; 34 35 struct emp_9 { // expected-warning {{struct has size 0 in C, non-zero size in C++}} 36 struct emp_1 f1; 37 union emp_2 f2; 38 }; 39 40 // Checks for pointer subtraction (PR15683) 41 struct emp_1 *func_1p(struct emp_1 *x) { return x - 5; } 42 43 int func_1() { 44 struct emp_1 v[1]; 45 return v - v; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}} 46 } 47 48 int func_2(struct emp_1 *x) { 49 return 1 + x - x; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}} 50 } 51 52 int func_3(struct emp_1 *x, struct emp_1 *y) { 53 return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}} 54 } 55 56 int func_4(struct emp_1 *x, const struct emp_1 *y) { 57 return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}} 58 } 59 60 int func_5(volatile struct emp_1 *x, const struct emp_1 *y) { 61 return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1' of zero size has undefined behavior}} 62 } 63 64 int func_6() { 65 union emp_2 v[1]; 66 return v - v; // expected-warning {{subtraction of pointers to type 'union emp_2' of zero size has undefined behavior}} 67 } 68 69 struct A; // expected-note {{forward declaration of 'struct A'}} 70 71 int func_7(struct A *x, struct A *y) { 72 return x - y; // expected-error {{arithmetic on a pointer to an incomplete type 'struct A'}} 73 } 74 75 int func_8(struct emp_1 (*x)[10], struct emp_1 (*y)[10]) { 76 return x - y; // expected-warning {{subtraction of pointers to type 'struct emp_1 [10]' of zero size has undefined behavior}} 77 } 78 79 int func_9(struct emp_1 (*x)[], struct emp_1 (*y)[]) { 80 return x - y; // expected-error {{arithmetic on a pointer to an incomplete type 'struct emp_1 []'}} 81 } 82 83 int func_10(int (*x)[0], int (*y)[0]) { 84 return x - y; // expected-warning {{subtraction of pointers to type 'int [0]' of zero size has undefined behavior}} 85 } 86