locale: add a stub that supports only the "C" locale (TEST)

This is enough to support the standard and likely the C++ library and
external programs to port, but also the most we can do without a proper
locale data storage and more target-specific developments that aren't a
priority right now.

CMakeLists.txt

@@ -59,6 +59,8 @@ endif()
 
 set(SOURCES
   src/libc/assert/assert.c
+  src/libc/locale/setlocale.c
+  src/libc/locale/localeconv.c
   src/libc/stdio/vsnprintf.c
   src/libc/stdio/sprintf.c
   src/libc/stdio/dprintf.c

include/locale.h

@@ -0,0 +1,43 @@
+#ifndef __LOCALE_H__
+# define __LOCALE_H__
+
+#include <stddef.h>
+
+struct lconv {
+	char *decimal_point;
+	char *thousands_sep;
+	char *grouping;
+	char *mon_decimal_point;
+	char *mon_thousands_sep;
+	char *mon_grouping;
+	char *positive_sign;
+	char *negative_sign;
+	char *currency_symbol;
+	char frac_digits;
+	char p_cs_precedes;
+	char n_cs_precedes;
+	char p_sep_by_space;
+	char n_sep_by_space;
+	char p_sign_posn;
+	char n_sign_posn;
+	char *int_curr_symbol;
+	char int_frac_digits;
+	char int_p_cs_precedes;
+	char int_n_cs_precedes;
+	char int_p_sep_by_space;
+	char int_n_sep_by_space;
+	char int_p_sign_posn;
+	char int_n_sign_posn;
+};
+
+#define LC_COLLATE   0
+#define LC_CTYPE     1
+#define LC_MONETARY  2
+#define LC_NUMERIC   3
+#define LC_TIME      4
+#define LC_ALL       5
+
+extern char *setlocale(int __category, char const *__locale);
+extern struct lconv *localeconv(void);
+
+#endif /*__LOCALE_H__*/

src/libc/locale/localeconv.c

@@ -0,0 +1,34 @@
+#include <locale.h>
+#include <limits.h>
+
+static struct lconv lconv_c = {
+	.decimal_point       = ".",
+	.thousands_sep       = "",
+	.grouping            = "",
+	.mon_decimal_point   = "",
+	.mon_thousands_sep   = "",
+	.mon_grouping        = "",
+	.positive_sign       = "",
+	.negative_sign       = "",
+	.currency_symbol     = "",
+	.frac_digits         = CHAR_MAX,
+	.p_cs_precedes       = CHAR_MAX,
+	.n_cs_precedes       = CHAR_MAX,
+	.p_sep_by_space      = CHAR_MAX,
+	.n_sep_by_space      = CHAR_MAX,
+	.p_sign_posn         = CHAR_MAX,
+	.n_sign_posn         = CHAR_MAX,
+	.int_curr_symbol     = "",
+	.int_frac_digits     = CHAR_MAX,
+	.int_p_cs_precedes   = CHAR_MAX,
+	.int_n_cs_precedes   = CHAR_MAX,
+	.int_p_sep_by_space  = CHAR_MAX,
+	.int_n_sep_by_space  = CHAR_MAX,
+	.int_p_sign_posn     = CHAR_MAX,
+	.int_n_sign_posn     = CHAR_MAX,
+};
+
+struct lconv *localeconv(void)
+{
+	return &lconv_c;
+}

src/libc/locale/setlocale.c

@@ -0,0 +1,18 @@
+#include <locale.h>
+
+/*
+** This stub locale implementation only supports the "C" locale. For several
+** targets there is no filesystem/LOCPATH/database of locale values, so this is
+** the only setting that can always be supported. It is also sufficient to
+** support when porting Linux programs because Linux does not guarantee that
+** other locales will be available.
+*/
+
+char *setlocale(__attribute__((unused)) int category, char const *locale)
+{
+	if(locale) {
+		if(locale[0] == 0) locale = "C";
+		if(locale[0] != 'C' || locale[1] != 0) return NULL;
+	}
+	return "C";
+}