getting a function to return a char array

**variable** · 02-07-2005

getting a function to return a char array, i couldnt find any tutorials that let me return a char array from a function.

im sure its a simple task, could anyone advise me on this?

thanks

**Thantos** · 02-07-2005

You can't pass arrays between functions. You can however put them into a structure and return a structure.

Bad:

Code:

char[10] foo (void)
{
  char bar[10] ="Hello";
  return bar;
}

Not Bad:

Code:

typedef struct {
  char bar[10];
} Ret;

Ret foo(void)
{
  Ret r = { "Hello" }
  return r;
}

**variable** · 02-07-2005

i tried getting the example you posted to work like this and couldnt

Code:

#include <stdio.h> 

typedef struct {
  char bar[10];
} pschar;

pschar postchar( void )
{
       pschar temp = {"my pschar"};
       printf("%s", temp);
          return temp;
          }

int main()
{

  printf("%s", postchar());
  getch();
  
  return 0;
}

**andyhunter** · 02-07-2005

Code:

#include <stdio.h> 

typedef struct {
  char bar[10];
} pschar;

pschar postchar( void )
{
	   pschar temp = {"my pschar"};
       printf("%s", temp.bar);
          return temp;
}

int main(void)
{

 
  printf("%s", (postchar()).bar);
  getchar();
  
  return 0;
}

The code you posted was trying to print out the stucture and not the character string.

**variable** · 02-07-2005

thanks, makes sense, forgot to do the .bar

that last printf wont work though, the one inside of the main

**andyhunter** · 02-07-2005

post your code because it is working fine for me.

**variable** · 02-07-2005

Code:

#include <stdio.h> 

typedef struct {
  char bar[10];
} pschar;

pschar postchar( void )
{
       pschar temp = {"my pschar"};
       printf("%s", temp.bar);
          return temp;
}

int main(void)
{

  printf("%s", (postchar()).bar);
  getchar();
  
  return 0;
}

**andyhunter** · 02-07-2005

And what exactly is happening?

**variable** · 02-07-2005

windows error

tester3.exe has encountered a problem and needs to close. We are sorry for the inconvenience.

**andyhunter** · 02-07-2005

hmm....interesting. Try this:

Code:

#include <stdio.h> 

typedef struct {
  char bar[10];
} pschar;

pschar postchar( void )
{
	   pschar temp = {"my pschar"};
       printf("%s", temp.bar);
          return temp;
}

int main(void)
{

  pschar myStruct = postchar();

  printf("\nIn main() %s", myStruct.bar);
  getchar();
  
  return 0;
}

**variable** · 02-07-2005

that worked, thats strange.

did the previous code that i posted work for you?

**andyhunter** · 02-07-2005

yes, its basically the same code I originally posted in response to your post. It may appear that your compiler was causing a pointer to be returned vice a copy of the object for the non working code sample. This would thus cause you to try to access a variable that was out of scope and thus potentially (well in your case) result in shutting down your program.

Just a theory though, maybe someone else has seen this before?

**variable** · 02-07-2005

cool, well thanks for the help; maybe someone else will shed some light on the situation.

**anonytmouse** · 02-07-2005

The typical (and far more efficient) solution is for the caller to allocate memory that the function can use. If you don't know the size of the returned string before calling the function you can use malloc and return a pointer.

Code:

void postchar1( char bar[] )
{
     strcpy(bar, "my pschar");
}

char* postchar2( void )
{
     char* bar = malloc(sizeof("my pschar"));

     if (bar != NULL)
         strcpy(bar, "my pschar");

     return bar;
}

int main(void)
{
    char  bar1[10];
    char* bar2;

    postchar1( bar1 );
    printf("%s\n", bar1);

    bar2 = postchar2();
    printf("%s\n", bar2);
    free(bar2);

    return 0;
}

**Dave Evans** · 02-08-2005

Originally Posted by andyhunter

Code:

#include <stdio.h> 

typedef struct {
  char bar[10];
} pschar;

pschar postchar( void )
{
       pschar temp = {"my pschar"};
       printf("%s", temp.bar);
          return temp;
}

int main(void)
{

 
  printf("%s", (postchar()).bar);
  getchar();
  
  return 0;
}

The code you posted was trying to print out the stucture and not the character string.

With this code:

gcc -Wall test.c
test.c: In function `main':
test.c:18: warning: format argument is not a pointer (arg 2)

..
..
(Program bombs)

However as c++:

g++ -Wall test.c
..
.. (No warnings)
.. (Program runs to completion)

Borland and Microsoft compilers accept C and C++ and execute to completion.

Any comments from the experts?

Regards,

Dave

Thread: getting a function to return a char array

Thread Tools

Search Thread

Display

getting a function to return a char array

Similar Threads

Compiling sample DarkGDK Program

Seg Fault in Compare Function

In over my head

Setting int pointers to one function (not using five functions!)

Half-life SDK, where are the constants?