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