Add a "fork" of musl as //fusl.

fusl/src/passwd/getgrouplist.c

+#define _GNU_SOURCE
+#include "pwf.h"
+#include <grp.h>
+#include <string.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <byteswap.h>
+#include <errno.h>
+#include "nscd.h"
+
+int getgrouplist(const char *user, gid_t gid, gid_t *groups, int *ngroups)
+{
+        int rv, nlim, ret = -1;
+        ssize_t i, n = 1;
+        struct group gr;
+        struct group *res;
+        FILE *f;
+        int swap = 0;
+        int32_t resp[INITGR_LEN];
+        uint32_t *nscdbuf = 0;
+        char *buf = 0;
+        char **mem = 0;
+        size_t nmem = 0;
+        size_t size;
+        nlim = *ngroups;
+        if (nlim >= 1) *groups++ = gid;
+
+        f = __nscd_query(GETINITGR, user, resp, sizeof resp, &swap);
+        if (!f) goto cleanup;
+        if (resp[INITGRFOUND]) {
+                nscdbuf = calloc(resp[INITGRNGRPS], sizeof(uint32_t));
+                if (!nscdbuf) goto cleanup;
+                if (!fread(nscdbuf, sizeof(*nscdbuf)*resp[INITGRNGRPS], 1, f)) {
+                        if (!ferror(f)) errno = EIO;
+                        goto cleanup;
+                }
+                if (swap) {
+                        for (i = 0; i < resp[INITGRNGRPS]; i++)
+                                nscdbuf[i] = bswap_32(nscdbuf[i]);
+                }
+        }
+        fclose(f);
+
+        f = fopen("/etc/group", "rbe");
+        if (!f && errno != ENOENT && errno != ENOTDIR)
+                goto cleanup;
+
+        if (f) {
+                while (!(rv = __getgrent_a(f, &gr, &buf, &size, &mem, &nmem, &res)) && res) {
+                        if (nscdbuf)
+                                for (i=0; i < resp[INITGRNGRPS]; i++) {
+                                        if (nscdbuf[i] == gr.gr_gid) nscdbuf[i] = gid;
+                                }
+                        for (i=0; gr.gr_mem[i] && strcmp(user, gr.gr_mem[i]); i++);
+                        if (!gr.gr_mem[i]) continue;
+                        if (++n <= nlim) *groups++ = gr.gr_gid;
+                }
+                if (rv) {
+                        errno = rv;
+                        goto cleanup;
+                }
+        }
+        if (nscdbuf) {
+                for(i=0; i < resp[INITGRNGRPS]; i++) {
+                        if (nscdbuf[i] != gid)
+                                if(++n <= nlim) *groups++ = nscdbuf[i];
+                }
+        }
+
+        ret = n > nlim ? -1 : n;
+        *ngroups = n;
+
+cleanup:
+        if (f) fclose(f);
+        free(nscdbuf);
+        free(buf);
+        free(mem);
+        return ret;
+}