How do I return multiple values from a function in C?

Question

If I have a function that produces a result int and a result string, how do I return them both from a function?

As far as I can tell I can only return one thing, as determined by the type preceding the function name.

Answer 1

I don't know what your string is, but I'm going to assume that it manages its own memory.

You have two solutions:

1: Return a struct which contains all the types you need.

struct Tuple {     int a;     string b; };  struct Tuple getPair() {     Tuple r = { 1, getString() };     return r; }  void foo() {     struct Tuple t = getPair(); } 

2: Use pointers to pass out values.

void getPair(int* a, string* b) {     // Check that these are not pointing to NULL     assert(a);     assert(b);     *a = 1;     *b = getString(); }  void foo() {     int a, b;     getPair(&a, &b); } 

Which one you choose to use depends largely on personal preference as to whatever semantics you like more.

Answer 2

Option 1: Declare a struct with an int and string and return a struct variable.

struct foo {      int bar1;  char bar2[MAX]; };  struct foo fun() {  struct foo fooObj;  ...  return fooObj; } 

Option 2: You can pass one of the two via pointer and make changes to the actual parameter through the pointer and return the other as usual:

int fun(char **param) {  int bar;  ...  strcpy(*param,"....");  return bar; } 

or

 char* fun(int *param) {  char *str = /* malloc suitably.*/  ...  strcpy(str,"....");  *param = /* some value */  return str; } 

Option 3: Similar to the option 2. You can pass both via pointer and return nothing from the function:

void fun(char **param1,int *param2) {  strcpy(*param1,"....");  *param2 = /* some calculated value */ }