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c++functionparametersvariadic-functionsvariadic
Serket
Serket

Reputation: 4485

Can va_lists in stdarg.h handle C++ references?

Can va_lists handle C++ references? I know they can handle ints, doubles and pointers, but not floats, chars, etc. Can they handle C++ references?

Upvotes: 0

Views: 137

Answers (1)

Tony Delroy
Tony Delroy

Reputation: 106246

You should #include <cstdarg> rather than <stdarg.h>...

If the caller provides a reference as an argument to such a function, the call will work the same way as if the referenced object was specified directly. For example, if you have:

void f(...);
T my_t;
T& x = my_t;
f(my_t);
f(x);

The values passed in registers and/or on the stack as arguments for f will be the same in both calls (assuming out-of line calls, and functionally equivalent if inlined).

So, "can they handle C++ references" - yes, in the way described above, which may or may not be what you wanted/expected.

Just a word of caution: if you have...

f(A& b, ...);

...the behaviour is undefined, as the va_start macro doesn't support having the final pre-...-matching argument be a reference (you can't pass a lambda capture nor pack expansion either). See C++ Standard [cstdarg.syn] paragraph 1 for full details.

Upvotes: 3

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