#define _GNU_SOURCE
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define DebugPointer(p)                                         \
    {                                                           \
        printf("%8s %20s: %p\n", #p, "address", (void*)&(p));  \
        printf("%8s %20s: %p\n", #p, "points to", (void*)(p)); \
    }
 
 
// memory-safe asprintf, implemented as a macro
#define Sasprintf(write_to, ...)            \
    {                                       \
        char* tmp = (write_to);             \
        printf("==== before asprintf\n");   \
        DebugPointer(tmp);                  \
        DebugPointer(write_to);             \
        asprintf(&(write_to), __VA_ARGS__); \
        printf("==== after  asprintf\n");   \
        DebugPointer(tmp);                  \
        DebugPointer(write_to);             \
        free(tmp);                          \
    }
 
int main() {
    char* s = NULL;
    int n = 0;
    Sasprintf(s, "%s", "aa\n");
    Sasprintf(s, "%s%s", s, "bb\n");
    Sasprintf(s, "%s%s", s, "cc\n");
    printf("string: %s\n", s);
    free(s);
}
 

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