user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/glibc/getgrouplist.c

@@ -0,0 +1,55 @@
+#include <assert.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int main() {
+	int ngroups = 100;
+	struct passwd *pw;
+	struct group *gr;
+	gid_t *groups;
+	bool gid_checked = false;
+	int e = 0;
+
+	groups = malloc(sizeof(*groups) * ngroups);
+	if(groups == NULL) {
+		perror("malloc");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Fetch passwd structure */
+	pw = getpwuid(geteuid());
+	if(pw == NULL) {
+		perror("getpwnam");
+		exit(EXIT_FAILURE);
+	}
+
+	/* Retrieve group list */
+	e = getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
+	assert(e > 0);
+	if(e == -1) {
+		fprintf(stderr, "getgrouplist() returned -1 (%s); ngroups = %d\n", strerror(errno), ngroups);
+		exit(EXIT_FAILURE);
+	}
+
+	/* Display list of retrieved groups, along with group names */
+	fprintf(stderr, "ngroups = %d\n", ngroups);
+	for(int j = 0; j < ngroups; j++) {
+		if(groups[j] == pw->pw_gid)
+			gid_checked = true;
+		printf("%d", groups[j]);
+		gr = getgrgid(groups[j]);
+		if(gr != NULL)
+			printf(" (%s)", gr->gr_name);
+		printf("\n");
+	}
+
+	assert(gid_checked);
+
+	exit(EXIT_SUCCESS);
+}