How to resolve “conflicting types error” in C?

Question

For the following C code (for swapping two numbers) I am getting the \"conflicting types\" error for swap function:

#include 
#includ         


        

Answer 1

The problem is that swap was not declared before it is used. Thus it is assigned a "default signature", one which will in this case not match its actual signature. Quote Andrey T:

The arguments are passed through a set of strictly defined conversions. int * pointers will be passed as int * pointers, for example. In other words, the parameter types are temporarily "deduced" from argument types. Only the return type is assumed to be int.

Aside from that, your code produces a bunch of other warnings. If using gcc, compile with -Wall -pedantic (or even with -Wextra), and be sure to fix each warning before continuing to program additional functionality. Also, you may want to tell the compiler whether you are writing ANSI C (-ansi) or C99 (-std=c99).

Some remarks:

• Put spaces after commas.
• Make main return an int.
  • And make it return 0 or return EXIT_SUCCESS.
• Import the definition of getch: #include .
  • Or just use getchar.
• Import the definition of memcpy: #include .
• Don't return something in a void function.

• You may want to use malloc to allocate a buffer of variable size. That will also work with older compilers:

  void swap(void *p1, void *p2, int size) {
      void *buffer = malloc(size);
      memcpy(buffer, p1, size);
      memcpy(p1, p2, size);
      memcpy(p2, buffer, size);
      free(buffer);
  }