From 767b23c4aa599ebefe0e344608e0c255cc32e45a Mon Sep 17 00:00:00 2001
From: implicitfield <114500360+implicitfield@users.noreply.github.com>
Date: Wed, 28 Sep 2022 22:01:54 +0300
Subject: [PATCH] LibC: Allow detection of supported locales through setlocale

Closes #14690
---
 Userland/Libraries/LibC/locale.cpp | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/Userland/Libraries/LibC/locale.cpp b/Userland/Libraries/LibC/locale.cpp
index 06cbcdb6ce..36ff8010d4 100644
--- a/Userland/Libraries/LibC/locale.cpp
+++ b/Userland/Libraries/LibC/locale.cpp
@@ -45,11 +45,19 @@ static struct lconv default_locale = {
     default_empty_value
 };
 
-char* setlocale(int, char const*)
+char* setlocale(int, char const* locale)
 {
-    static char locale[2];
-    memcpy(locale, "C", 2);
-    return locale;
+    static char c_locale_string[2];
+    memcpy(c_locale_string, "C", 2);
+
+    // If we get a null pointer, return the current locale as per POSIX spec.
+    if (locale == nullptr)
+        return c_locale_string;
+
+    if (strcmp(locale, "POSIX") == 0 || strcmp(locale, "C") == 0 || strcmp(locale, "") == 0)
+        return c_locale_string;
+
+    return nullptr;
 }
 
 struct lconv* localeconv()