stringsapi.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char **func_that_returns_strings(int nstrings) {
    // first dump all the strings into a contiguous buffer, separated by \0

    char buf[100];
    size_t size = 0;
    for (int i = 0; i < nstrings; i++)
        size += sprintf(buf + size, "qqq%dzzz", i) + 1;


    // then allocate a buffer for the pointers, with extra space at the end

    char **strings = malloc(sizeof *strings * (nstrings + 1) + size);
    char *newbuf = (char *)(strings + (nstrings + 1));
    memcpy(newbuf, buf, size);

    char **s = strings;
    *s = newbuf;

    for (char *p = newbuf; p < newbuf + size; p++)
        if (!*p)
            *++s = p+1;

    *s = NULL;

    return strings;
}

int main() {
    char **strings = func_that_returns_strings(5);

    for (char **s = strings; *s; s++)
        puts(*s);

    // everything gets freed in a single call
    free(strings);
}