From f95fc91e4f0cd9837b109b9354a6b3fb8a42a0fc Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sat, 1 Jan 2022 16:05:21 +0100
Subject: [PATCH] LibCore: Reset `errno` before using LibC pwd functions

We should not expect LibC functions to clear `errno` on success,
so if we want to use it for error checking after a call, we need
to clear it before the call.
---
 Userland/Libraries/LibCore/System.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Userland/Libraries/LibCore/System.cpp b/Userland/Libraries/LibCore/System.cpp
index 462aa65236..92ab111dcd 100644
--- a/Userland/Libraries/LibCore/System.cpp
+++ b/Userland/Libraries/LibCore/System.cpp
@@ -404,6 +404,8 @@ ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid)
 
 ErrorOr<Optional<struct passwd>> getpwnam(StringView name)
 {
+    errno = 0;
+
     ::setpwent();
     if (errno)
         return Error::from_syscall("getpwnam"sv, -errno);
@@ -422,6 +424,8 @@ ErrorOr<Optional<struct passwd>> getpwnam(StringView name)
 
 ErrorOr<Optional<struct group>> getgrnam(StringView name)
 {
+    errno = 0;
+
     ::setgrent();
     if (errno)
         return Error::from_syscall("getgrnam"sv, -errno);