Question

The following code works differently on 64 bit and on 32 bit which is causing me trouble to port my code.

char * tmp = "How are you?";
printf("size of char * = %ld and size of strtok return val = %ld \n",sizeof(char *),sizeof(strtok(tmp," ")));

Following is the output:

32 bit: 
size of char * = 4 and size of strtok return val = 4 

64 bit:

size of char * = 8 and size of strtok return val = 4

The man page of strtok says:

   #include <string.h>

   char *strtok(char *str, const char *delim);

RETURN VALUE
       The strtok() and strtok_r() functions return a pointer to the next token, or NULL if there are no more tokens.

The char* on a 64 bit machine is supposed to be 8 bytes as printed. So why is strtok returning a 4 bytes char pointer on a 64 bit machine??

Thanks

Answer 1

You forgot to #include <string.h>.

This is causing the default return type of int to be inferred by the compiler. By #including the right header file, the correct prototype is pulled into scope.

This solves the problem for me on gcc. If it doesn’t for you, what compiler are you using?