diff --git a/libc/Android.mk b/libc/Android.mk
index 26da523..d0c9218 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -292,7 +292,7 @@
 	bionic/sched_cpucount.c \
 	bionic/semaphore.c \
 	bionic/sha1.c \
-	bionic/stubs.c \
+	bionic/stubs.cpp \
 	bionic/system_properties.c \
 	bionic/tdelete.c \
 	bionic/tdestroy.c \
diff --git a/libc/bionic/stubs.c b/libc/bionic/stubs.c
deleted file mode 100644
index d140890..0000000
--- a/libc/bionic/stubs.c
+++ /dev/null
@@ -1,525 +0,0 @@
-/*
- * Copyright (C) 2008 The Android Open Source Project
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *  * Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- *  * Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the
- *    distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <ctype.h>
-#include <errno.h>
-#include <grp.h>
-#include <mntent.h>
-#include <netdb.h>
-#include <private/android_filesystem_config.h>
-#include <private/logd.h>
-#include <pthread.h>
-#include <pwd.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-
-static int do_getpw_r(int by_name, const char* name, uid_t uid,
-        struct passwd* dst, char* buf, size_t byte_count, struct passwd** result)
-{
-    /*
-     * getpwnam_r and getpwuid_r don't modify errno, but library calls we
-     *  make might.
-     */
-    int old_errno = errno;
-    int rc = 0;
-    *result = NULL;
-
-    const struct passwd* src = by_name ? getpwnam(name) : getpwuid(uid);
-
-    /*
-     * POSIX allows failure to find a match to be considered a non-error.
-     * Reporting success (0) but with *result NULL is glibc's behavior.
-     */
-    if (src == NULL) {
-        rc = (errno == ENOENT) ? 0 : errno;
-        goto failure;
-    }
-
-    /*
-     * Work out where our strings will go in 'buf', and whether we've got
-     * enough space.
-     */
-    size_t required_byte_count = 0;
-    dst->pw_name = buf;
-    required_byte_count += strlen(src->pw_name) + 1;
-    dst->pw_dir = buf + required_byte_count;
-    required_byte_count += strlen(src->pw_dir) + 1;
-    dst->pw_shell = buf + required_byte_count;
-    required_byte_count += strlen(src->pw_shell) + 1;
-    if (byte_count < required_byte_count) {
-        rc = ERANGE;
-        goto failure;
-    }
-
-    /* Copy the strings. */
-    snprintf(buf, byte_count, "%s%c%s%c%s",
-            src->pw_name, 0, src->pw_dir, 0, src->pw_shell);
-
-    /*
-     * pw_passwd is non-POSIX and unused (always NULL) in bionic.
-     * pw_gecos is non-POSIX and missing in bionic.
-     */
-    dst->pw_passwd = NULL;
-
-    /* Copy the integral fields. */
-    dst->pw_gid = src->pw_gid;
-    dst->pw_uid = src->pw_uid;
-
-success:
-    rc = 0;
-    *result = dst;
-failure:
-    errno = old_errno;
-    return rc;
-}
-
-int getpwnam_r(const char* name, struct passwd* pwd,
-        char* buf, size_t byte_count, struct passwd** result)
-{
-    return do_getpw_r(1, name, -1, pwd, buf, byte_count, result);
-}
-
-int getpwuid_r(uid_t uid, struct passwd* pwd,
-        char* buf, size_t byte_count, struct passwd** result)
-{
-    return do_getpw_r(0, NULL, uid, pwd, buf, byte_count, result);
-}
-
-/** Thread-specific state for the stubs functions
- **/
-
-static pthread_once_t   the_once = PTHREAD_ONCE_INIT;
-static pthread_key_t    the_key;
-
-typedef struct {
-    struct passwd  passwd;
-    struct group   group;
-    char*          group_members[2];
-    char           app_name_buffer[32];
-    char           group_name_buffer[32];
-} stubs_state_t;
-
-static void
-stubs_state_free( void*  _s )
-{
-    stubs_state_t*  s = _s;
-    free(s);
-}
-
-static stubs_state_t*
-stubs_state_alloc( void )
-{
-    stubs_state_t*  s = calloc(1, sizeof *s);
-
-    if (s != NULL) {
-        s->group.gr_mem = s->group_members;
-    }
-    return s;
-}
-
-static void __stubs_key_init(void)
-{
-    pthread_key_create( &the_key, stubs_state_free );
-}
-
-static stubs_state_t*
-__stubs_state(void)
-{
-    stubs_state_t*  s;
-
-    pthread_once(&the_once, __stubs_key_init);
-    s = pthread_getspecific(the_key);
-    if (s == NULL) {
-        s = stubs_state_alloc();
-        if (s == NULL) {
-            errno = ENOMEM;  /* just in case */
-        } else {
-            if ( pthread_setspecific(the_key, s) != 0 ) {
-                stubs_state_free(s);
-                errno = ENOMEM;
-                s     = NULL;
-            }
-        }
-    }
-    return s;
-}
-
-static struct passwd*
-android_iinfo_to_passwd( struct passwd          *pw,
-                         struct android_id_info *iinfo )
-{
-    pw->pw_name  = (char*)iinfo->name;
-    pw->pw_uid   = iinfo->aid;
-    pw->pw_gid   = iinfo->aid;
-    pw->pw_dir   = "/";
-    pw->pw_shell = "/system/bin/sh";
-    return pw;
-}
-
-static struct group*
-android_iinfo_to_group( struct group *gr,
-                        struct android_id_info *iinfo )
-{
-    gr->gr_name   = (char*) iinfo->name;
-    gr->gr_gid    = iinfo->aid;
-    gr->gr_mem[0] = gr->gr_name;
-    gr->gr_mem[1] = NULL;
-    return gr;
-}
-
-static struct passwd *
-android_id_to_passwd( struct passwd *pw, unsigned id)
-{
-    struct android_id_info *iinfo = android_ids;
-    unsigned n;
-    for (n = 0; n < android_id_count; n++) {
-        if (iinfo[n].aid == id) {
-            return android_iinfo_to_passwd(pw, iinfo + n);
-        }
-    }
-    return NULL;
-}
-
-static struct passwd*
-android_name_to_passwd(struct passwd *pw, const char *name)
-{
-    struct android_id_info *iinfo = android_ids;
-    unsigned n;
-    for (n = 0; n < android_id_count; n++) {
-        if (!strcmp(iinfo[n].name, name)) {
-            return android_iinfo_to_passwd(pw, iinfo + n);
-        }
-    }
-    return NULL;
-}
-
-static struct group*
-android_id_to_group( struct group *gr, unsigned id )
-{
-    struct android_id_info *iinfo = android_ids;
-    unsigned n;
-    for (n = 0; n < android_id_count; n++) {
-        if (iinfo[n].aid == id) {
-            return android_iinfo_to_group(gr, iinfo + n);
-        }
-    }
-    return NULL;
-}
-
-static struct group*
-android_name_to_group( struct group *gr, const char *name )
-{
-    struct android_id_info *iinfo = android_ids;
-    unsigned n;
-    for (n = 0; n < android_id_count; n++) {
-        if (!strcmp(iinfo[n].name, name)) {
-            return android_iinfo_to_group(gr, iinfo + n);
-        }
-    }
-    return NULL;
-}
-
-/* translate a user/group name to the corresponding user/group id.
- * u0_a1234 -> 0 * AID_USER + AID_APP + 1234
- * u2_i1000 -> 2 * AID_USER + AID_ISOLATED_START + 1000
- * u1_system -> 1 * AID_USER + android_ids['system']
- * returns 0 and sets errno to ENOENT in case of error
- */
-static unsigned
-app_id_from_name( const char*  name )
-{
-    unsigned long  userid;
-    unsigned long  appid = 0;
-    char*          end;
-
-    if (name[0] != 'u' || !isdigit(name[1]))
-        goto FAIL;
-
-    userid = strtoul(name+1, &end, 10);
-    if (end[0] != '_' || end[1] == 0)
-        goto FAIL;
-
-    if (end[1] == 'a' && isdigit(end[2])) {
-        /* end will point to \0 if the strtoul below succeeds. */
-        appid = strtoul(end+2, &end, 10) + AID_APP;
-    } else if (end[1] == 'i' && isdigit(end[2])) {
-        /* end will point to \0 if the strtoul below succeeds. */
-        appid = strtoul(end+2, &end, 10) + AID_ISOLATED_START;
-    } else {
-        for (size_t n = 0; n < android_id_count; n++) {
-            if (!strcmp(android_ids[n].name, end + 1)) {
-                appid = android_ids[n].aid;
-                /* move the end pointer to the null terminator */
-                end += 1 + strlen(android_ids[n].name);
-            }
-        }
-    }
-
-    /* check if the entire string was consumed by the 3 cases above */
-    if (end[0] != 0)
-        goto FAIL;
-
-    /* check that user id won't overflow */
-    if (userid > 1000)
-        goto FAIL;
-
-    /* check that app id is within range */
-    if (appid >= AID_USER)
-        goto FAIL;
-
-    return (unsigned)(appid + userid*AID_USER);
-
-FAIL:
-    errno = ENOENT;
-    return 0;
-}
-
-static void
-print_app_uid_name(uid_t  uid, char* buffer, int bufferlen)
-{
-    uid_t appid;
-    uid_t userid;
-
-    appid = uid % AID_USER;
-    userid = uid / AID_USER;
-
-    if (appid < AID_ISOLATED_START) {
-        if (appid < AID_APP) {
-            for (size_t n = 0; n < android_id_count; n++) {
-                if (android_ids[n].aid == appid) {
-                    snprintf(buffer, bufferlen, "u%u_%s", userid, android_ids[n].name);
-                    return;
-                }
-            }
-        }
-        snprintf(buffer, bufferlen, "u%u_a%u", userid, appid - AID_APP);
-    } else {
-        snprintf(buffer, bufferlen, "u%u_i%u", userid, appid - AID_ISOLATED_START);
-    }
-}
-
-/* translate a uid into the corresponding name.
- * 0 to AID_APP-1                   -> "system", "radio", etc.
- * AID_APP to AID_ISOLATED_START-1  -> u0_a1234
- * AID_ISOLATED_START to AID_USER-1 -> u0_i1234
- * AID_USER+                        -> u1_radio, u1_a1234, u2_i1234, etc.
- * returns a passwd structure (sets errno to ENOENT on failure)
- */
-static struct passwd*
-app_id_to_passwd(uid_t  uid, stubs_state_t*  state)
-{
-    struct passwd*  pw = &state->passwd;
-
-    if (uid < AID_APP) {
-        errno = ENOENT;
-        return NULL;
-    }
-
-    print_app_uid_name(uid, state->app_name_buffer, sizeof state->app_name_buffer);
-
-    pw->pw_name  = state->app_name_buffer;
-    pw->pw_dir   = "/data";
-    pw->pw_shell = "/system/bin/sh";
-    pw->pw_uid   = uid;
-    pw->pw_gid   = uid;
-
-    return pw;
-}
-
-/* translate a gid into the corresponding app_<gid>
- * group structure (sets errno to ENOENT on failure)
- */
-static struct group*
-app_id_to_group(gid_t  gid, stubs_state_t*  state)
-{
-    struct group*  gr = &state->group;
-    int appid;
-    int userid;
-
-    if (gid < AID_APP) {
-        errno = ENOENT;
-        return NULL;
-    }
-
-    print_app_uid_name(gid, state->group_name_buffer, sizeof state->group_name_buffer);
-
-    gr->gr_name   = state->group_name_buffer;
-    gr->gr_gid    = gid;
-    gr->gr_mem[0] = gr->gr_name;
-    gr->gr_mem[1] = NULL;
-
-    return gr;
-}
-
-
-struct passwd*
-getpwuid(uid_t uid)
-{
-    stubs_state_t*  state = __stubs_state();
-    struct passwd*  pw;
-
-    if (state == NULL)
-        return NULL;
-
-    pw = &state->passwd;
-
-    if ( android_id_to_passwd(pw, uid) != NULL )
-        return pw;
-
-    return app_id_to_passwd(uid, state);
-}
-
-struct passwd*
-getpwnam(const char *login)
-{
-    stubs_state_t*  state = __stubs_state();
-
-    if (state == NULL)
-        return NULL;
-
-    if (android_name_to_passwd(&state->passwd, login) != NULL)
-        return &state->passwd;
-
-    return app_id_to_passwd( app_id_from_name(login), state );
-}
-
-int
-getgrouplist (const char *user, gid_t group,
-              gid_t *groups, int *ngroups)
-{
-    if (*ngroups < 1) {
-        *ngroups = 1;
-        return -1;
-    }
-    groups[0] = group;
-    return (*ngroups = 1);
-}
-
-char*
-getlogin(void)
-{
-    struct passwd *pw = getpwuid(getuid());
-
-    if(pw) {
-        return pw->pw_name;
-    } else {
-        return NULL;
-    }
-}
-
-struct group*
-getgrgid(gid_t gid)
-{
-    stubs_state_t*  state = __stubs_state();
-    struct group*   gr;
-
-    if (state == NULL)
-        return NULL;
-
-    gr = android_id_to_group(&state->group, gid);
-    if (gr != NULL)
-        return gr;
-
-    return app_id_to_group(gid, state);
-}
-
-struct group*
-getgrnam(const char *name)
-{
-    stubs_state_t*  state = __stubs_state();
-    unsigned        id;
-
-    if (state == NULL)
-        return NULL;
-
-    if (android_name_to_group(&state->group, name) != 0)
-        return &state->group;
-
-    return app_id_to_group( app_id_from_name(name), state );
-}
-
-static void unimplemented_stub(const char* function) {
-  const char* fmt = "%s(3) is not implemented on Android\n";
-  __libc_android_log_print(ANDROID_LOG_WARN, "libc", fmt, function);
-  fprintf(stderr, fmt, function);
-}
-
-#define UNIMPLEMENTED unimplemented_stub(__PRETTY_FUNCTION__)
-
-struct netent* getnetbyname(const char* name) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-void endpwent(void) {
-  UNIMPLEMENTED;
-}
-
-struct mntent* getmntent(FILE* f) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-char* ttyname(int fd) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-int ttyname_r(int fd, char* buf, size_t buflen) {
-  UNIMPLEMENTED;
-  return -ERANGE;
-}
-
-struct netent* getnetbyaddr(uint32_t net, int type) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-struct protoent* getprotobyname(const char* name) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-struct protoent* getprotobynumber(int proto) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-char* getusershell(void) {
-  UNIMPLEMENTED;
-  return NULL;
-}
-
-void setusershell(void) {
-  UNIMPLEMENTED;
-}
-
-void endusershell(void) {
-  UNIMPLEMENTED;
-}
diff --git a/libc/bionic/stubs.cpp b/libc/bionic/stubs.cpp
new file mode 100644
index 0000000..652e522
--- /dev/null
+++ b/libc/bionic/stubs.cpp
@@ -0,0 +1,461 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <ctype.h>
+#include <errno.h>
+#include <grp.h>
+#include <mntent.h>
+#include <netdb.h>
+#include <private/android_filesystem_config.h>
+#include <private/logd.h>
+#include <pthread.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+// Thread-specific state for the non-reentrant functions.
+static pthread_once_t stubs_once = PTHREAD_ONCE_INIT;
+static pthread_key_t stubs_key;
+struct stubs_state_t {
+  passwd passwd_;
+  group group_;
+  char* group_members_[2];
+  char app_name_buffer_[32];
+  char group_name_buffer_[32];
+  char dir_buffer_[32];
+  char sh_buffer_[32];
+};
+
+static int do_getpw_r(int by_name, const char* name, uid_t uid,
+                      passwd* dst, char* buf, size_t byte_count,
+                      passwd** result) {
+  // getpwnam_r and getpwuid_r don't modify errno, but library calls we
+  // make might.
+  int old_errno = errno;
+  *result = NULL;
+
+  // Our implementation of getpwnam(3) and getpwuid(3) use thread-local
+  // storage, so we can call them as long as we copy everything out
+  // before returning.
+  const passwd* src = by_name ? getpwnam(name) : getpwuid(uid); // NOLINT: see above.
+
+  // POSIX allows failure to find a match to be considered a non-error.
+  // Reporting success (0) but with *result NULL is glibc's behavior.
+  if (src == NULL) {
+    int rc = (errno == ENOENT) ? 0 : errno;
+    errno = old_errno;
+    return rc;
+  }
+
+  // Work out where our strings will go in 'buf', and whether we've got
+  // enough space.
+  size_t required_byte_count = 0;
+  dst->pw_name = buf;
+  required_byte_count += strlen(src->pw_name) + 1;
+  dst->pw_dir = buf + required_byte_count;
+  required_byte_count += strlen(src->pw_dir) + 1;
+  dst->pw_shell = buf + required_byte_count;
+  required_byte_count += strlen(src->pw_shell) + 1;
+  if (byte_count < required_byte_count) {
+    errno = old_errno;
+    return ERANGE;
+  }
+
+  // Copy the strings.
+  snprintf(buf, byte_count, "%s%c%s%c%s",
+           src->pw_name, 0, src->pw_dir, 0, src->pw_shell);
+
+  // pw_passwd is non-POSIX and unused (always NULL) in bionic.
+  // pw_gecos is non-POSIX and missing in bionic.
+  dst->pw_passwd = NULL;
+
+  // Copy the integral fields.
+  dst->pw_gid = src->pw_gid;
+  dst->pw_uid = src->pw_uid;
+
+  *result = dst;
+  errno = old_errno;
+  return 0;
+}
+
+int getpwnam_r(const char* name, passwd* pwd,
+               char* buf, size_t byte_count, passwd** result) {
+  return do_getpw_r(1, name, -1, pwd, buf, byte_count, result);
+}
+
+int getpwuid_r(uid_t uid, passwd* pwd,
+               char* buf, size_t byte_count, passwd** result) {
+  return do_getpw_r(0, NULL, uid, pwd, buf, byte_count, result);
+}
+
+static stubs_state_t* stubs_state_alloc() {
+  stubs_state_t*  s = reinterpret_cast<stubs_state_t*>(calloc(1, sizeof(*s)));
+  if (s != NULL) {
+    s->group_.gr_mem = s->group_members_;
+  }
+  return s;
+}
+
+static void stubs_state_free(void* ptr) {
+  stubs_state_t* state = reinterpret_cast<stubs_state_t*>(ptr);
+  free(state);
+}
+
+static void __stubs_key_init() {
+  pthread_key_create(&stubs_key, stubs_state_free);
+}
+
+static stubs_state_t* __stubs_state() {
+  pthread_once(&stubs_once, __stubs_key_init);
+  stubs_state_t* s =
+      reinterpret_cast<stubs_state_t*>(pthread_getspecific(stubs_key));
+  if (s == NULL) {
+    s = stubs_state_alloc();
+    if (s == NULL) {
+      errno = ENOMEM;  // Just in case.
+    } else {
+      if (pthread_setspecific(stubs_key, s) != 0) {
+        stubs_state_free(s);
+        errno = ENOMEM;
+        s = NULL;
+      }
+    }
+  }
+  return s;
+}
+
+static passwd* android_iinfo_to_passwd(stubs_state_t* state,
+                                       const android_id_info* iinfo) {
+  snprintf(state->dir_buffer_, sizeof(state->dir_buffer_), "/");
+  snprintf(state->sh_buffer_, sizeof(state->sh_buffer_), "/system/bin/sh");
+
+  passwd* pw = &state->passwd_;
+  pw->pw_name  = (char*) iinfo->name;
+  pw->pw_uid   = iinfo->aid;
+  pw->pw_gid   = iinfo->aid;
+  pw->pw_dir   = state->dir_buffer_;
+  pw->pw_shell = state->sh_buffer_;
+  return pw;
+}
+
+static group* android_iinfo_to_group(group* gr,
+                                     const android_id_info* iinfo) {
+  gr->gr_name   = (char*) iinfo->name;
+  gr->gr_gid    = iinfo->aid;
+  gr->gr_mem[0] = gr->gr_name;
+  gr->gr_mem[1] = NULL;
+  return gr;
+}
+
+static passwd* android_id_to_passwd(stubs_state_t* state, unsigned id) {
+  for (size_t n = 0; n < android_id_count; ++n) {
+    if (android_ids[n].aid == id) {
+      return android_iinfo_to_passwd(state, android_ids + n);
+    }
+  }
+  return NULL;
+}
+
+static passwd* android_name_to_passwd(stubs_state_t* state, const char* name) {
+  for (size_t n = 0; n < android_id_count; ++n) {
+    if (!strcmp(android_ids[n].name, name)) {
+      return android_iinfo_to_passwd(state, android_ids + n);
+    }
+  }
+  return NULL;
+}
+
+static group* android_id_to_group(group* gr, unsigned id) {
+  for (size_t n = 0; n < android_id_count; ++n) {
+    if (android_ids[n].aid == id) {
+      return android_iinfo_to_group(gr, android_ids + n);
+    }
+  }
+  return NULL;
+}
+
+static group* android_name_to_group(group* gr, const char* name) {
+  for (size_t n = 0; n < android_id_count; ++n) {
+    if (!strcmp(android_ids[n].name, name)) {
+      return android_iinfo_to_group(gr, android_ids + n);
+    }
+  }
+  return NULL;
+}
+
+// Translate a user/group name to the corresponding user/group id.
+// u0_a1234 -> 0 * AID_USER + AID_APP + 1234
+// u2_i1000 -> 2 * AID_USER + AID_ISOLATED_START + 1000
+// u1_system -> 1 * AID_USER + android_ids['system']
+// returns 0 and sets errno to ENOENT in case of error
+static unsigned app_id_from_name(const char* name) {
+  if (name[0] != 'u' || !isdigit(name[1])) {
+    errno = ENOENT;
+    return 0;
+  }
+
+  char* end;
+  unsigned long userid = strtoul(name+1, &end, 10);
+  if (end[0] != '_' || end[1] == 0) {
+    errno = ENOENT;
+    return 0;
+  }
+
+  unsigned long appid = 0;
+  if (end[1] == 'a' && isdigit(end[2])) {
+    // end will point to \0 if the strtoul below succeeds.
+    appid = strtoul(end+2, &end, 10) + AID_APP;
+  } else if (end[1] == 'i' && isdigit(end[2])) {
+    // end will point to \0 if the strtoul below succeeds.
+    appid = strtoul(end+2, &end, 10) + AID_ISOLATED_START;
+  } else {
+    for (size_t n = 0; n < android_id_count; n++) {
+      if (!strcmp(android_ids[n].name, end + 1)) {
+        appid = android_ids[n].aid;
+        // Move the end pointer to the null terminator.
+        end += strlen(android_ids[n].name) + 1;
+      }
+    }
+  }
+
+  // Check that the entire string was consumed by one of the 3 cases above.
+  if (end[0] != 0) {
+    errno = ENOENT;
+    return 0;
+  }
+
+  // Check that user id won't overflow.
+  if (userid > 1000) {
+    errno = ENOENT;
+    return 0;
+  }
+
+  // Check that app id is within range.
+  if (appid >= AID_USER) {
+    errno = ENOENT;
+    return 0;
+  }
+
+  return (unsigned)(appid + userid*AID_USER);
+}
+
+static void print_app_uid_name(uid_t  uid, char* buffer, int bufferlen) {
+  uid_t appid = uid % AID_USER;
+  uid_t userid = uid / AID_USER;
+
+  if (appid < AID_ISOLATED_START) {
+    if (appid < AID_APP) {
+      for (size_t n = 0; n < android_id_count; n++) {
+        if (android_ids[n].aid == appid) {
+          snprintf(buffer, bufferlen, "u%u_%s", userid, android_ids[n].name);
+          return;
+        }
+      }
+    }
+    snprintf(buffer, bufferlen, "u%u_a%u", userid, appid - AID_APP);
+  } else {
+    snprintf(buffer, bufferlen, "u%u_i%u", userid, appid - AID_ISOLATED_START);
+  }
+}
+
+// Translate a uid into the corresponding name.
+// 0 to AID_APP-1                   -> "system", "radio", etc.
+// AID_APP to AID_ISOLATED_START-1  -> u0_a1234
+// AID_ISOLATED_START to AID_USER-1 -> u0_i1234
+// AID_USER+                        -> u1_radio, u1_a1234, u2_i1234, etc.
+// returns a passwd structure (sets errno to ENOENT on failure).
+static passwd* app_id_to_passwd(uid_t uid, stubs_state_t* state) {
+  passwd* pw = &state->passwd_;
+
+  if (uid < AID_APP) {
+    errno = ENOENT;
+    return NULL;
+  }
+
+  print_app_uid_name(uid, state->app_name_buffer_,
+                     sizeof(state->app_name_buffer_));
+
+  snprintf(state->dir_buffer_, sizeof(state->dir_buffer_), "/data");
+  snprintf(state->sh_buffer_, sizeof(state->sh_buffer_), "/system/bin/sh");
+
+  pw->pw_name  = state->app_name_buffer_;
+  pw->pw_dir   = state->dir_buffer_;
+  pw->pw_shell = state->sh_buffer_;
+  pw->pw_uid   = uid;
+  pw->pw_gid   = uid;
+
+  return pw;
+}
+
+// Translate a gid into the corresponding app_<gid>
+// group structure (sets errno to ENOENT on failure).
+static group* app_id_to_group(gid_t gid, stubs_state_t* state) {
+  if (gid < AID_APP) {
+    errno = ENOENT;
+    return NULL;
+  }
+
+  print_app_uid_name(gid, state->group_name_buffer_,
+                     sizeof(state->group_name_buffer_));
+
+  group* gr = &state->group_;
+  gr->gr_name   = state->group_name_buffer_;
+  gr->gr_gid    = gid;
+  gr->gr_mem[0] = gr->gr_name;
+  gr->gr_mem[1] = NULL;
+  return gr;
+}
+
+
+passwd* getpwuid(uid_t uid) { // NOLINT: implementing bad function.
+  stubs_state_t* state = __stubs_state();
+  if (state == NULL) {
+    return NULL;
+  }
+
+  passwd* pw = android_id_to_passwd(state, uid);
+  if (pw != NULL) {
+    return pw;
+  }
+  return app_id_to_passwd(uid, state);
+}
+
+passwd* getpwnam(const char* login) { // NOLINT: implementing bad function.
+  stubs_state_t* state = __stubs_state();
+  if (state == NULL) {
+    return NULL;
+  }
+
+  passwd* pw = android_name_to_passwd(state, login);
+  if (pw != NULL) {
+    return pw;
+  }
+  return app_id_to_passwd(app_id_from_name(login), state);
+}
+
+int getgrouplist(const char* user, gid_t group, gid_t* groups, int* ngroups) {
+    if (*ngroups < 1) {
+        *ngroups = 1;
+        return -1;
+    }
+    groups[0] = group;
+    return (*ngroups = 1);
+}
+
+char* getlogin() { // NOLINT: implementing bad function.
+  passwd *pw = getpwuid(getuid()); // NOLINT: implementing bad function in terms of bad function.
+  return (pw != NULL) ? pw->pw_name : NULL;
+}
+
+group* getgrgid(gid_t gid) { // NOLINT: implementing bad function.
+  stubs_state_t* state = __stubs_state();
+  if (state == NULL) {
+    return NULL;
+  }
+
+  group* gr = android_id_to_group(&state->group_, gid);
+  if (gr != NULL) {
+    return gr;
+  }
+
+  return app_id_to_group(gid, state);
+}
+
+group* getgrnam(const char* name) { // NOLINT: implementing bad function.
+  stubs_state_t* state = __stubs_state();
+  if (state == NULL) {
+    return NULL;
+  }
+
+  if (android_name_to_group(&state->group_, name) != 0) {
+    return &state->group_;
+  }
+
+  return app_id_to_group(app_id_from_name(name), state);
+}
+
+static void unimplemented_stub(const char* function) {
+  const char* fmt = "%s(3) is not implemented on Android\n";
+  __libc_android_log_print(ANDROID_LOG_WARN, "libc", fmt, function);
+  fprintf(stderr, fmt, function);
+}
+
+#define UNIMPLEMENTED unimplemented_stub(__PRETTY_FUNCTION__)
+
+netent* getnetbyname(const char* name) {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+void endpwent() {
+  UNIMPLEMENTED;
+}
+
+mntent* getmntent(FILE* f) {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+char* ttyname(int fd) { // NOLINT: implementing bad function.
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+int ttyname_r(int fd, char* buf, size_t buflen) {
+  UNIMPLEMENTED;
+  return -ERANGE;
+}
+
+netent* getnetbyaddr(uint32_t net, int type) {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+protoent* getprotobyname(const char* name) {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+protoent* getprotobynumber(int proto) {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+char* getusershell() {
+  UNIMPLEMENTED;
+  return NULL;
+}
+
+void setusershell() {
+  UNIMPLEMENTED;
+}
+
+void endusershell() {
+  UNIMPLEMENTED;
+}