the code doesn't look that wrong, but

• the caller should allways check for errors

• if (length < 1) test unnecessary

• srand(time(NULL) should be done outside

• error catching (malloc) should open no new block

• short isn't really at the high of the time, use it only for serilizing/deserilizing raw binary files/network data

• use unsigned if it makes sense, the counter can't be negative and this is not lala-java-land (besides it can be a bit faster but most times it doesn't matter) (side note, yes i am damaged from looking at the assembler output of the compilers)

   #include <string.h>
   #include <time.h>
  
   char *randstring(int length) {    
       char *string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789,.-#'?!";
       size_t stringLen = strlen(string);        
       char *randomString;
  
       randomString = malloc(sizeof(char) * (length +1));
  
       if (!randomString) {
           return (char*)0;
       }
  
       unsigned int key = 0;
  
       for (int n = 0;n < length;n++) {            
           key = rand() % stringLen;          
           randomString[n] = string[key];
       }
  
       randomString[length] = '\0';
  
       return randomString;
   }
  

the code doesn't look that wrong, but

• the caller should allways check for errors

• if (length < 1) test unnecessary

• srand(time(NULL) should be done outside

• error catching (malloc) should open no new block

• short isn't really at the high of the time, use it only for serilizing/deserilizing raw binary files/network data

• use unsigned if it makes sense, the counter can't be negative and this is not lala-java-land (besides it can be a bit faster but most times it doesn't matter) (side note, yes i am damaged from looking at the assembler output of the compilers)

• you don't need to recalculate the string length everytime, with C++0x you can maybe let it calculate from the compiler on compiletime

   #include <string.h>
   #include <time.h>
  
   char *randstring(int length) {    
       char *string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789,.-#'?!";
       size_t stringLen = 26*2+10+7;        
       char *randomString;
  
       randomString = malloc(sizeof(char) * (length +1));
  
       if (!randomString) {
           return (char*)0;
       }
  
       unsigned int key = 0;
  
       for (int n = 0;n < length;n++) {            
           key = rand() % stringLen;          
           randomString[n] = string[key];
       }
  
       randomString[length] = '\0';
  
       return randomString;
   }