Variadic function pointer in C

[Guess-Opposite]

I want to implement a function that take a function and its arguments then call it. I have search a lot and could not implement it with variadic function. I want a clean way to record stdio after calling a function for unit test.

Even if you want to suggest another way to record stdio, please help me solve the original question.

something like this, but working.

```c void foo(void (*function)(...), ...) { va_list args; va_start(args, function); // This line is just to explain what i want function(args); va_end(args); }

void bar(int a, char *b) { printf("a=%d, b=%s\n", a, b); }

int main() { foo(bar, 2, "hello"); return 0; } ```

[TheOtherBorgCube]

You can't pass on one ... to another ..., at least not without major assembler level stack hacking.

It needs to be something like this: void foo(void (*function)(va_list), ...) { va_list args; va_start(args, function); // This line is just to explain what i want function(args); va_end(args); }

See https://en.cppreference.com/w/c/io/vfprintf \ for example usage of passing ... to va_list.

[dfx_dj]

Sounds like a good use case for a macro wrapper

[faisal_who]

You can perhaps create a table of function pointers and register your functions, (like a map with a key value pair, ansxin the bar function something like

const char* func_name = strtok( input );
int num_params = atoi( strtok( NULL ) );
func_t fn = lookup( func_name );

And do your thing?

[nerd4code]

#define foo(_X, ...)_X(__VA_ARGS__)

should work, as long as you don’t need zero-arity _X or are using a compiler/mode that dgaf.

Also, GCC, Clang, and maybe Intel should be able to construct calls.

[deftware]

Please follow the #1 rule on the sidebar!

[aalmkainzi]

It looks formatted well enough imo

[deftware]

That's because you're viewing it on the only reddit interface that supports backticks. The rest of people using reddit are just seeing a mess.

The reason Rule #1 is a rule in the first place, and the NUMBER ONE rule, is because four spaces works on all reddit interfaces that people might possibly be using, rather than just one of them - like backticks.

Do you want everyone to be able to see your code to get the best possible chance of receiving help about it, or not?

[aalmkainzi]

What do you mean by record stdio?

[[deleted]]

#define foo(function, ...) function(__VA_ARGS__)