Implement getgroups

src/platform/redox/mod.rs

@@ -611,10 +611,52 @@ impl Pal for Sys {
         redox_rt::sys::posix_getresugid().rgid as gid_t
     }
 
-    fn getgroups(list: Out<[gid_t]>) -> Result<c_int> {
-        // TODO
-        todo_skip!(0, "getgroups({}, {:p}): not implemented", list.len(), list);
-        Err(Errno(ENOSYS))
+    fn getgroups(mut list: Out<[gid_t]>) -> Result<c_int> {
+        // FIXME: this operation doesn't scale when group/passwd file grows
+
+        let uid = Self::geteuid();
+        let pwd = crate::header::pwd::getpwuid(uid);
+
+        if pwd.is_null() {
+            return Err(Errno(ENOENT));
+        }
+
+        let username = unsafe { CStr::from_ptr((*pwd).pw_name) };
+        let username = username.to_bytes_with_nul();
+        let mut count = 0;
+
+        unsafe {
+            use crate::header::grp;
+            grp::setgrent();
+
+            while let Some(grp) = grp::getgrent().as_ref() {
+                let mut i = 0;
+                let mut found = false;
+
+                while !(*grp.gr_mem.offset(i)).is_null() {
+                    let member = CStr::from_ptr(*grp.gr_mem.offset(i));
+                    if member.to_bytes_with_nul() == username {
+                        found = true;
+                        break;
+                    }
+                    i += 1;
+                }
+
+                if found {
+                    if !list.is_empty() && (count as usize) < list.len() {
+                        list.index(count).write(grp.gr_gid);
+                    }
+                    count += 1;
+                }
+            }
+            grp::endgrent();
+        }
+
+        if !list.is_empty() && (count as usize) > list.len() {
+            return Err(Errno(EINVAL));
+        }
+
+        Ok(count as i32)
     }
 
     fn getpagesize() -> usize {

tests/Makefile

@@ -305,6 +305,7 @@ VARIED_NAMES=\
 	pthread/timeout \
 	pthread/tls \
 	grp/getgrouplist \
+	grp/getgroups \
 	grp/getgrgid_r \
 	grp/getgrnam_r \
 	grp/gr_iter \

tests/grp/getgroups.c

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <grp.h>
+
+int main() {
+    gid_t primary_gid = getegid();
+    struct group *pg = getgrgid(primary_gid);
+
+    printf("getegid: %u (%s)\n", primary_gid, pg ? pg->gr_name : "?");
+
+    int count = getgroups(0, NULL);
+    gid_t *list = malloc(sizeof(gid_t) * count);
+    getgroups(count, list);
+
+    printf("getgroups: %d\n", count);
+    for (int i = 0; i < count; i++) {
+        struct group *sg = getgrgid(list[i]);
+        
+        printf("  - %u (%s)\n", list[i], sg ? sg->gr_name : "?");
+    }
+
+    free(list);
+    return 0;
+}