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

fusl/src/passwd/getpwent_a.c

+#include "pwf.h"
+#include <pthread.h>
+
+static unsigned atou(char **s)
+{
+        unsigned x;
+        for (x=0; **s-'0'<10U; ++*s) x=10*x+(**s-'0');
+        return x;
+}
+
+int __getpwent_a(FILE *f, struct passwd *pw, char **line, size_t *size, struct passwd **res)
+{
+        ssize_t l;
+        char *s;
+        int rv = 0;
+        int cs;
+        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
+        for (;;) {
+                if ((l=getline(line, size, f)) < 0) {
+                        rv = ferror(f) ? errno : 0;
+                        free(*line);
+                        *line = 0;
+                        pw = 0;
+                        break;
+                }
+                line[0][l-1] = 0;
+
+                s = line[0];
+                pw->pw_name = s++;
+                if (!(s = strchr(s, ':'))) continue;
+
+                *s++ = 0; pw->pw_passwd = s;
+                if (!(s = strchr(s, ':'))) continue;
+
+                *s++ = 0; pw->pw_uid = atou(&s);
+                if (*s != ':') continue;
+
+                *s++ = 0; pw->pw_gid = atou(&s);
+                if (*s != ':') continue;
+
+                *s++ = 0; pw->pw_gecos = s;
+                if (!(s = strchr(s, ':'))) continue;
+
+                *s++ = 0; pw->pw_dir = s;
+                if (!(s = strchr(s, ':'))) continue;
+
+                *s++ = 0; pw->pw_shell = s;
+                break;
+        }
+        pthread_setcancelstate(cs, 0);
+        *res = pw;
+        if (rv) errno = rv;
+        return rv;
+}