Is there a maximum number of parameters for functions in C with the gcc (resp. MinGW) compiler?

Question

I know that I would never hit such a limit when following good practices. However, I need to use an automatically generated function with lots of parameters (and I cannot change anything with it, I receive the function from someone else).

So: What is the maximum number of parameters I can use in gcc resp. MinGW?

I've found this about the C++ language specification. And this about the C language standard limits. What I am interested in is the question what the "real world" limits / implementation details are. Especially in gcc and MinGW.

Also: What kind of error message could I expect when hitting such a limit? And when using C Code in a C++ application via the extern "C" declaration, does this make any difference to the "normal" C limit? Might other limits than the number of parameters apply here, e.g. something like a maximum line length? Or the maximum stack size?

Thanks!

Answer 1

the C Standard 5.2.4.1 says:

4095 characters in a logical source line
127 parameters in one function definition
127 arguments in one function call

also the stack size (1MB - 8MB) is a limit, if you have huge structs as arguments.

But all these limits are far away from all what's good practice.

https://gcc.gnu.org/onlinedocs/gcc-4.3.5/cpp/Implementation-limits.html says that gcc has much higher limits (limited only by available memory).

Answer 2

In C there are special librarys (stdarg.h) for multiple parameters. With this library you can write functions like this:

int a_function ( int x, ... )
{
    va_list a_list;
    va_start( a_list, x );
}

And i don't think there is a particular limit.

---

Here is a example how to use this library: (Credits to: http://www.cprogramming.com/tutorial/c/lesson17.html)

#include <stdarg.h>
#include <stdio.h>

/* this function will take the number of values to average
   followed by all of the numbers to average */
double average ( int num, ... )
{
    va_list arguments;                     
    double sum = 0;

    /* Initializing arguments to store all values after num */
    va_start ( arguments, num );           
    /* Sum all the inputs; we still rely on the function caller to tell us how
     * many there are */
    for ( int x = 0; x < num; x++ )        
    {
        sum += va_arg ( arguments, double ); 
    }
    va_end ( arguments );                  // Cleans up the list

    return sum / num;                      
}

int main()
{
    /* this computes the average of 13.2, 22.3 and 4.5 (3 indicates the number of values to average) */
    printf( "%f\n", average ( 3, 12.2, 22.3, 4.5 ) );
    /* here it computes the average of the 5 values 3.3, 2.2, 1.1, 5.5 and 3.3
    printf( "%f\n", average ( 5, 3.3, 2.2, 1.1, 5.5, 3.3 ) );
}