| // RUN: %clang_cc1 -verify -ffreestanding -Wpre-c2x-compat -std=c2x %s |
| |
| /* WG14 N2975: partial |
| * Relax requirements for va_start |
| */ |
| |
| #include <stdarg.h> |
| |
| #define DERP this is an error |
| |
| void func(...) { // expected-warning {{'...' as the only parameter of a function is incompatible with C standards before C23}} |
| // Show that va_start doesn't require the second argument in C23 mode. |
| va_list list; |
| va_start(list); // FIXME: it would be nice to issue a portability warning to C17 and earlier here. |
| va_end(list); |
| |
| // Show that va_start doesn't expand or evaluate the second argument. |
| va_start(list, DERP); |
| va_end(list); |
| |
| // FIXME: it would be kinder to diagnose this instead of silently accepting it. |
| va_start(list, 1, 2); |
| va_end(list); |
| |
| // We didn't change the behavior of __builtin_va_start (and neither did GCC). |
| __builtin_va_start(list); // expected-error {{too few arguments to function call, expected 2, have 1}} |
| |
| // Verify that the return type of a call to va_start is 'void'. |
| _Static_assert(__builtin_types_compatible_p(__typeof__(va_start(list)), void), ""); |
| _Static_assert(__builtin_types_compatible_p(__typeof__(__builtin_va_start(list, 0)), void), ""); |
| } |
| |
| // Show that function pointer types also don't need an argument before the |
| // ellipsis. |
| typedef void (*fp)(...); // expected-warning {{'...' as the only parameter of a function is incompatible with C standards before C23}} |
| |
| // Passing something other than the argument before the ... is still not valid. |
| void diag(int a, int b, ...) { |
| va_list list; |
| // FIXME: the call to va_start should also diagnose the same way as the call |
| // to __builtin_va_start. However, because va_start is not allowed to expand |
| // or evaluate the second argument, we can't pass it along to |
| // __builtin_va_start to get that diagnostic. So in C17 and earlier, we will |
| // diagnose this use through the macro, but in C23 and later we've lost the |
| // diagnostic entirely. GCC has the same issue currently. |
| va_start(list, a); |
| // However, the builtin itself is under no such constraints regarding |
| // expanding or evaluating the second argument, so it can still diagnose. |
| __builtin_va_start(list, a); // expected-warning {{second argument to 'va_start' is not the last named parameter}} |
| va_end(list); |
| } |
| |
| void foo(int a...); // expected-error {{C requires a comma prior to the ellipsis in a variadic function type}} |
| |
| void use(void) { |
| // Demonstrate that we can actually call the variadic function when it has no |
| // formal parameters. |
| func(1, '2', 3.0, "4"); |
| func(); |
| |
| // And that assignment still works as expected. |
| fp local = func; |
| |
| // ...including conversion errors. |
| fp other_local = diag; // expected-error {{incompatible function pointer types initializing 'fp' (aka 'void (*)(...)') with an expression of type 'void (int, int, ...)'}} |
| } |