Function overloading in C

add.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int addi(int a, int b) {
    return a + b;
}

char *adds(char *a, char *b) {
    char *res = malloc(strlen(a) + strlen(b) + 1);
    strcpy(res, a);
    strcat(res, b);
    return res;
}

#define add(a, b) _Generic(a, int: addi, char*: adds)(a, b)

int main(void) {
    int a = 1, b = 2;
    printf("%d\n", add(a, b)); // 3

    char *c = "hello ", *d = "world";
    printf("%s\n", add(c, d)); // hello world

    return 0;
}

I wonder if this'll work on the Arduino.

I wonder if this'll work on the Arduino.

works as advertised on osx.

works as advertised on osx.

@jasiek, if you can find a C11 compiler for Arduino. GCC supports the _Generic portion of C11 since 4.9, so it should work with avr-gcc-4.9 or newer.

@jasiek, if you can find a C11 compiler for Arduino. GCC supports the _Generic portion of C11 since 4.9, so it should work with avr-gcc-4.9 or newer.

You create a memory leak by not storing a pointer to the concatenated string before printing it, since now you can't free it after you malloc'd it.

You create a memory leak by not storing a pointer to the concatenated string before printing it, since now you can't free it after you malloc'd it.

clang provides __attribute__((overloadable)), which enables a limited version of C++-style name-mangling based polymorphism, so that you don't have to write a _Generic wrapper for each function.

clang provides __attribute__((overloadable)), which enables a limited version of C++-style name-mangling based polymorphism, so that you don't have to write a _Generic wrapper for each function.

Here's another example I wrote the other day, that's actually useful: number parsing, regardless of its type: parse_number().

Here's another example I wrote the other day, that's actually useful: number parsing, regardless of its type: parse_number().

@2mac memory is freed at line 25 😄

OT: thanks for the interesting stuff...

@2mac memory is freed at line 25 😄

OT: thanks for the interesting stuff...

Without C11:

#define NARG_(_15, _14, _13, _12, _11, _10, _9, _8, _7, _6, _5, _4, _3, _2, _1, N, ...) N
#define NARG(...) NARG_(__VA_ARGS__, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
#define PASTE(a, b) a ## b
#define XPASTE(a, b) PASTE(a, b)

int foo(int a, int b) {
    return 1;
}
#define foo2(a,b) foo((a), (b))
#define foo1(x) foo2(x,0)
#define foo(...) XPASTE(foo, NARG(__VA_ARGS__))(__VA_ARGS__)

Without C11:

#define NARG_(_15, _14, _13, _12, _11, _10, _9, _8, _7, _6, _5, _4, _3, _2, _1, N, ...) N
#define NARG(...) NARG_(__VA_ARGS__, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
#define PASTE(a, b) a ## b
#define XPASTE(a, b) PASTE(a, b)

int foo(int a, int b) {
    return 1;
}
#define foo2(a,b) foo((a), (b))
#define foo1(x) foo2(x,0)
#define foo(...) XPASTE(foo, NARG(__VA_ARGS__))(__VA_ARGS__)

http://stackoverflow.com/questions/479207/function-overloading-in-c/13010401#13010401

http://stackoverflow.com/questions/479207/function-overloading-in-c/13010401#13010401

Is there a way to do stricter type checking on more than one argument? As I read this, it is only checking the type of the first argument?

Is there a way to do stricter type checking on more than one argument? As I read this, it is only checking the type of the first argument?

1. Type checking only on one argument

2. main leaks memory

1. Type checking only on one argument

2. main leaks memory

@thelonewolf https://github.com/nautical/CBullet/blob/master/pie.h

@thelonewolf https://github.com/nautical/CBullet/blob/master/pie.h

@theonewolf https://github.com/nautical/CBullet/blob/master/pie.h

@theonewolf https://github.com/nautical/CBullet/blob/master/pie.h

@jasiek: The Arduino IDE uses C++, so function overloading works just fine. (So do templates, but you have to define them in a .h file rather than the default extension-less file.)

@jasiek: The Arduino IDE uses C++, so function overloading works just fine. (So do templates, but you have to define them in a .h file rather than the default extension-less file.)

@KLuka
It's not good practice to not free something you've malloc'd.

@KLuka
It's not good practice to not free something you've malloc'd.

Still not supported by Intel C compiler though.

Still not supported by Intel C compiler though.

@nautical Submitted: http://stackoverflow.com/a/31640391/293064

@nautical Submitted: http://stackoverflow.com/a/31640391/293064

@dubslow Yes, main leaks memory. I realize now that github has its own "grammar police" since that was not the point of this gist.

@dubslow Yes, main leaks memory. I realize now that github has its own "grammar police" since that was not the point of this gist.

@Fusion I'd say it's not github, but C community, as memory leaks is something to avoid even in examples that are this simple.

@Fusion I'd say it's not github, but C community, as memory leaks is something to avoid even in examples that are this simple.

DAE notice the memory leak???????????????

DAE notice the memory leak???????????????

OMG did you guys see the memory leak?!!

OMG did you guys see the memory leak?!!

'a' gets evaluated twice

'a' gets evaluated twice

There is a memory leak. You allocate with malloc but you never free the allocated memory. You should fix that.

There is a memory leak. You allocate with malloc but you never free the allocated memory. You should fix that.