A possible solution is to make the parameter type a container that can be initialized by a brace initializer list, such as std::initializer_list<int> or std::vector<int>. For example: #include <iostream> #include <initializer_list> void func(std::initializer_list<int> a_args) { for (auto i: a_args) std::cout << i << ‘\n’; } int main() { func({4, 7}); func({4, 7, 12, 14}); }
You can use various recursive macro techniques to do things with variadic macros. For example, you can define a NUM_ARGS macro that counts the number of arguments to a variadic macro: #define _NUM_ARGS(X100, X99, X98, X97, X96, X95, X94, X93, X92, X91, X90, X89, X88, X87, X86, X85, X84, X83, X82, X81, X80, X79, X78, … Read more
The trick is that you tell them somehow else. For printf you have to supply a format string which even contains type information (which might be incorrect though). The way to supply this information is mainly user-contract and often error-prone. As for calling conventions: Usually the arguments are pushed onto the stack from left to … Read more
Variadic functions use a calling convention where the caller is responsible for popping the function parameters from the stack, so yes, it is possible to do this dynamically. It’s not standardized in C, and normally would require some assembly to manually push the desired parameters, and invoke the variadic function correctly. The cdecl calling convention … Read more
You can’t do this, at least not in the way you’re wanting to do it. What you want to do (pass on the variable arguments) requires having an initializer on UIAlertView that accepts a va_list. There isn’t one. However, you can use the addButtonWithTitle: method: + (void)showWithTitle:(NSString *)title message:(NSString *)message delegate:(id)delegate cancelButtonTitle:(NSString *)cancelButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, … Read more
Another possibility, which does not use sizeof nor a GCC extension is to add the following to your code #define PP_COMMASEQ_N() \ 1, 1, 1, 1, \ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, \ 1, 1, 1, 1, 1, 1, … Read more
With params you can call your method like this: addTwoEach(1, 2, 3, 4, 5); Without params, you can’t. Additionally, you can call the method with an array as a parameter in both cases: addTwoEach(new int[] { 1, 2, 3, 4, 5 }); That is, params allows you to use a shortcut when calling the method. … Read more
Here is my homework of the day, it’s based on macro tricks and today I particularly learnt about __VA_NARG__ invented by Laurent Deniau. Anyway, the following sample code works up to 8 fields for the sake of clarity. Just extend the code by duplicating if you need more (this is because the preprocessor doesn’t feature … Read more
C99 way, also supported by VC++ compiler. #define FOO(fmt, …) printf(fmt, ##__VA_ARGS__)
If you don’t have a function analogous to vfprintf that takes a va_list instead of a variable number of arguments, you can’t do it. See http://c-faq.com/varargs/handoff.html. Example: void myfun(const char *fmt, va_list argp) { vfprintf(stderr, fmt, argp); }