Add tests for new locale.h functions

tests/Makefile

@@ -46,7 +46,9 @@ EXPECT_NAMES=\
 	glob \
 	iso646 \
 	libgen \
-	locale \
+	locale/duplocale \
+	locale/newlocale \
+	locale/setlocale \
 	math \
 	regex \
 	select \

tests/locale/duplocale.c

@@ -0,0 +1,39 @@
+#include <locale.h>
+#include <stdio.h>
+#include <assert.h>
+#include <stdint.h>
+
+int main() {
+    struct lconv *lconv0 = localeconv();
+
+    locale_t locale0 = uselocale(NULL);
+    assert(locale0 == LC_GLOBAL_LOCALE);
+
+    locale_t locale1 = uselocale(LC_GLOBAL_LOCALE);
+    assert(locale1 == LC_GLOBAL_LOCALE);
+
+    struct lconv *lconv1 = localeconv();
+    assert(lconv0 == lconv1);
+    
+    locale_t locale2 = newlocale(LC_ALL_MASK, "C", (locale_t)0);
+    assert(locale2 != LC_GLOBAL_LOCALE);
+
+    struct lconv *lconv2 = localeconv();
+    assert(lconv2 == lconv1);
+    
+    locale_t locale3 = duplocale(locale2);
+    assert(locale3 != locale2);
+    assert(locale3 != LC_GLOBAL_LOCALE);
+
+    locale_t locale4 = uselocale(locale3);
+    assert(locale4 == locale1);
+
+    struct lconv *lconv3 = localeconv();
+    assert(lconv3 != lconv2);
+
+    // should not crash
+    freelocale(locale3);
+    freelocale(locale2);
+    freelocale(locale1);
+    return 0;
+}

tests/locale/newlocale.c

@@ -0,0 +1,16 @@
+#include <locale.h>
+#include <stdio.h>
+#include <assert.h>
+#include <stdint.h>
+
+int main() {    
+    locale_t locale0 = newlocale(LC_ALL_MASK, "C", (locale_t)0);
+    assert(locale0 != (locale_t)0);
+
+    locale_t locale1 = newlocale(LC_ALL_MASK, "non-existent-locale", (locale_t)0);
+    assert(locale1 == (locale_t)0);
+
+    // TODO: test with existing custom locale
+
+    return 0;
+}