source: azure_iot_hub/trunk/musl-1.1.18/src/passwd/getgr_r.c@ 388

#include "pwf.h"
#include <pthread.h>

#define FIX(x) (gr->gr_##x = gr->gr_##x-line+buf)

static int getgr_r(const char *name, gid_t gid, struct group *gr, char *buf, size_t size, struct group **res)
{
        char *line = 0;
        size_t len = 0;
        char **mem = 0;
        size_t nmem = 0;
        int rv = 0;
        size_t i;
        int cs;

        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);

        rv = __getgr_a(name, gid, gr, &line, &len, &mem, &nmem, res);
        if (*res && size < len + (nmem+1)*sizeof(char *) + 32) {
                *res = 0;
                rv = ERANGE;
        }
        if (*res) {
                buf += (16-(uintptr_t)buf)%16;
                gr->gr_mem = (void *)buf;
                buf += (nmem+1)*sizeof(char *);
                memcpy(buf, line, len);
                FIX(name);
                FIX(passwd);
                for (i=0; mem[i]; i++)
                        gr->gr_mem[i] = mem[i]-line+buf;
                gr->gr_mem[i] = 0;
        }
        free(mem);
        free(line);
        pthread_setcancelstate(cs, 0);
        if (rv) errno = rv;
        return rv;
}

int getgrnam_r(const char *name, struct group *gr, char *buf, size_t size, struct group **res)
{
        return getgr_r(name, 0, gr, buf, size, res);
}

int getgrgid_r(gid_t gid, struct group *gr, char *buf, size_t size, struct group **res)
{
        return getgr_r(0, gid, gr, buf, size, res);
}