clang/test/C/C11/n1330.c

   1 // RUN: %clang_cc1 -verify -Wgnu-folding-constant %s
   2
   3 /* WG14 N1330: Yes
   4  * Static assertions
   5  */
   6
   7 // Test syntactic requirements: first argument must be a constant expression,
   8 // and the second argument must be a string literal. We support the C2x
   9 // extension that allows you to elide the second argument.
  10 int a;
  11 _Static_assert(a, ""); // expected-error {{static assertion expression is not an integral constant expression}}
  12 _Static_assert(1);     // expected-warning {{'_Static_assert' with no message is a C23 extension}}
  13
  14 // Test functional requirements
  15 _Static_assert(1, "this works");
  16 _Static_assert(0, "this fails"); // expected-error {{static assertion failed: this fails}}
  17 _Static_assert(0); // expected-error {{static assertion failed}} \
  18                       expected-warning {{'_Static_assert' with no message is a C23 extension}}
  19
  20 // Test declaration contexts. We've already demonstrated that file scope works.
  21 struct S {
  22   _Static_assert(1, "this works");
  23   union U {
  24     long l;
  25     _Static_assert(1, "this works");
  26   } u;
  27   enum E {
  28     _Static_assert(1, "this should not compile"); // expected-error {{expected identifier}}
  29     One
  30   } e;
  31 };
  32
  33 void func(                                     // expected-note {{to match this '('}}
  34   _Static_assert(1, "this should not compile") // expected-error {{expected parameter declarator}} \
  35                                                   expected-error {{expected ')'}}
  36 );
  37 void func(                                     // expected-note {{to match this '('}}
  38   _Static_assert(1, "this should not compile") // expected-error {{expected parameter declarator}} \
  39                                                   expected-error {{expected ')'}}
  40 ) {}
  41
  42 void test(void) {
  43   _Static_assert(1, "this works");
  44   _Static_assert(0, "this fails"); // expected-error {{static assertion failed: this fails}}
  45
  46   // The use of a _Static_assert in a for loop declaration is prohibited per
  47   // 6.8.5p3 requiring the declaration to only declare identifiers for objects
  48   // having auto or register storage class; a static assertion does not declare
  49   // an identifier nor an object.
  50   // FIXME: this diagnostic is pretty terrible.
  51   int i = 0;
  52   for (_Static_assert(1, "this should not compile"); i < 10; ++i) // expected-error {{expected identifier or '('}} \
  53                                                                      expected-error {{expected ';' in 'for' statement specifier}}
  54     ;
  55
  56   // Ensure that only an integer constant expression can be used as the
  57   // controlling expression.
  58   _Static_assert(1.0f, "this should not compile"); // expected-warning {{expression is not an integer constant expression; folding it to a constant is a GNU extension}}
  59 }
  60
  61 #if __STDC_VERSION__ < 202311L
  62 // The use of a _Static_assert in a K&R C function definition is prohibited per
  63 // 6.9.1p6 requiring each declaration to have a declarator (which a static
  64 // assertion does not have) and only declare identifiers from the identifier
  65 // list.
  66 // The error about expecting a ';' is due to the static assertion confusing the
  67 // compiler. It'd be nice if we improved the diagnostics here, but because this
  68 // involves a K&R C declaration, it's low priority.
  69 void knr(a, b, c) // expected-warning {{a function definition without a prototype is deprecated in all versions of C and is not supported in C23}}
  70   int a, b; // expected-error {{expected ';' at end of declaration}}
  71   _Static_assert(1, "this should not compile"); // expected-error {{expected identifier or '('}} \
  72                                                    expected-error {{type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int}}
  73   float c;
  74 {
  75 }
  76 #endif // __STDC_VERSION__