Add string to string in C with safe functions

Question

I want to copy the file name to a string and add ".cpt" to it. But I can not do this with safe functions (strcat_s). Error: "The line is not terminated by zero!". And I set '\ 0', how to fix it using safe functions?

size = strlen(locatie); size++; nieuw = (char*)malloc(size+4); strcpy_s(nieuw, size, locatie); nieuw[size] = '\0'; strcat_s(nieuw, 4, ".cpt"); // <-- crash puts(nieuw); 

Answer 1

The size parameter of _s functions is the size of the destination buffer, not the source. The error is that in the nieuw character there is no null terminator in the first for characters. Try the following:

 size = strlen(locatie); size++; int nieuwSize = size + 4; nieuw = (char*)malloc(nieuwSize ); strcpy_s(nieuw, nieuwSize, locatie); nieuw[size] = '\0'; strcat_s(nieuw, nieuwSize, ".cpt"); // <-- crash puts(nieuw); 

Answer 2

Why not

 size = strlen(locatie); size++; nieuw = (char*)malloc(size+6); strcpy_s(nieuw, size, locatie); strcat_s(nieuw, 4, ".cpt"); puts(nieuw); nieuw[size + 5] = '\0'; 

Answer 3

Check out asprintf . It allows you to print on a line such as printf

Answer 4

 size = strlen(locatie); size++; nieuw = (char*)malloc(size+4); strcpy_s(nieuw, size, locatie); nieuw[size] = '\0'; strcat_s(nieuw, size, ".cpt"); puts(nieuw) 

;

Answer 5

Maybe some standard solution?

 const char * const SUFFIX = ".cpt"; size = strlen(locatie) + strlen(SUFFIX) + 1; // +1 for NULL nieuw = (char*)malloc(size); snprintf(nieuw, size, "%s%s", locatie, SUFFIX); 

Answer 6

 #include <stdio.h> #include <stdlib.h> #include <string.h> int main(void) { char old[] = "hello"; size_t size = strlen(old) + 5;; char *new_name = (char*)malloc(size); new_name[size-1] = '\0'; strcpy_s(new_name, size, old); strcat_s(new_name, size, ".cpp"); printf("%s\n", new_name); return 0; }