Add USE_POSIX_SETLOCALE option

Add USE_POSIX_SETLOCALE option for platforms missing uselocale().
Document locale options in README, Makefile & rockspec.

Also:
- Rename USE_POSIX_LOCALE define to USE_POSIX_USELOCALE.
- Use uselocale() by default through Makefile (Linux, OSX).
- Use setlocale() by default through rockspec (other platforms).

5 files changed, 52 insertions, 13 deletions

diff --git a/Makefile b/Makefile
index 5857aee..082c720 100644
--- a/Makefile
+++ b/Makefile
@@ -23,8 +23,12 @@ override CFLAGS += -fpic -I$(LUA_INCLUDE_DIR) -DVERSION=\"$(CJSON_VERSION)\"
 # Handle Solaris platforms that are missing isinf().
 #override CFLAGS +=  -DUSE_INTERNAL_ISINF
 # Handle locales that use comma as a decimal separator on locale aware
-# platforms. Requires POSIX-1.2008 support.
-override CFLAGS +=  -DUSE_POSIX_LOCALE
+# platforms (optional, but recommended).
+# USE_POSIX_USELOCALE: Linux, OSX. Thread safe. Recommended option.
+# USE_POSIX_SETLOCALE: Works on all ANSI C platforms. May be used when
+#                      thread-safety isn't required.
+override CFLAGS +=  -DUSE_POSIX_USELOCALE
+#override CFLAGS +=  -DUSE_POSIX_SETLOCALE
 
 INSTALL ?= install
 
diff --git a/README b/README
index e8c3abe..f863d73 100644
--- a/README
+++ b/README
@@ -309,6 +309,18 @@ Lua CJSON will generate an error if asked to serialise Lua functions,
 userdata, lightuserdata or threads.
 
 
+Locale handling
+---------------
+
+Lua CJSON uses strtod() and snprintf() to perform numeric conversion
+as they are usually well supported, fast and bug free.
+
+To ensure JSON encoding/decoding works correctly for locales using
+comma decimal separators, Lua CJSON must be compiled with either
+USE_POSIX_USELOCALE or USE_POSIX_SETLOCALE. See the Makefile or the
+rockspec for details.
+
+
 References
 ==========
 
diff --git a/TODO b/TODO
index 9dbde9c..1345448 100644
--- a/TODO
+++ b/TODO
@@ -2,5 +2,3 @@
   - Optionally create an object for settings. Clone function.
 
 - Convert documentation into structured source format
-
-- Add setlocale() support for non-POSIX 2008 operating systems
diff --git a/lua-cjson-1.0.3-1.rockspec b/lua-cjson-1.0.3-1.rockspec
index 3f8e981..28514e1 100644
--- a/lua-cjson-1.0.3-1.rockspec
+++ b/lua-cjson-1.0.3-1.rockspec
@@ -25,9 +25,12 @@ build = {
         cjson = {
             sources = { "lua_cjson.c", "strbuf.c" },
 -- Optional workarounds:
+-- USE_POSIX_USELOCALE: Linux, OSX. Thread safe. Recommended.
+-- USE_POSIX_SETLOCALE: Works on all ANSI C platforms. May be used when
+--                      thread-safety isn't required.
 -- USE_INTERNAL_ISINF: Provide internal isinf() implementation. Required
 --                     on some Solaris platforms.
-            defines = { "VERSION=\"1.0.3\"" }
+            defines = { "VERSION=\"1.0.3\"", "USE_POSIX_SETLOCALE" }
         }
     },
     copy_directories = { "tests" }
diff --git a/lua_cjson.c b/lua_cjson.c
index ad3818d..8efd127 100644
--- a/lua_cjson.c
+++ b/lua_cjson.c
@@ -44,26 +44,46 @@
 
 #include "strbuf.h"
 
-#ifdef USE_POSIX_LOCALE
-/* Reset locale to POSIX for strtod() / sprintf().
+/* Support to reset locale to POSIX for strtod() / sprintf().
  * Some locales use comma as a decimal separator. This breaks JSON. */
+#ifdef USE_POSIX_USELOCALE
+
+#ifdef USE_POSIX_SETLOCALE
+#error Must not define USE_POSIX_USELOCALE and USE_POSIX_SETLOCALE simultaneously.
+#endif
 
 /* unistd.h defines _POSIX_VERSION */
 #include <unistd.h>
+
 #if _POSIX_VERSION >= 200809L
 /* POSIX.1-2008 adds threadsafe locale support */
 #include <locale.h>
 #elif defined(_POSIX_VERSION)
-/* Some pre-POSIX.1-2008 operating systems use xlocale.h instead */
+/* Some pre-POSIX.1-2008 operating systems offer xlocale.h instead */
 #include <xlocale.h>
 #else
 #error Missing _POSIX_VERSION define
-#endif
+#endif  /* _POSIX_VERSION */
+
 #define LOCALE_SET_POSIX(x) (x)->saved_locale = uselocale((x)->posix_locale)
 #define LOCALE_RESTORE(x)   uselocale((x)->saved_locale)
-#else
+
+#elif defined(USE_POSIX_SETLOCALE)
+/* ANSI C / ISO C90 implementation. Not thread-safe, affects entire process. */
+#include <locale.h>
+
+#define LOCALE_SET_POSIX(x) \
+    do { \
+        (x)->saved_locale = setlocale(LC_NUMERIC, NULL); \
+        setlocale(LC_NUMERIC, "C"); \
+    } while(0)
+#define LOCALE_RESTORE(x)   setlocale(LC_NUMERIC, (x)->saved_locale)
+
+#else   /* Do not work around locale support in strtod() / sprintf() */
+
 #define LOCALE_SET_POSIX(x) do { } while(0)
 #define LOCALE_RESTORE(x)   do { } while(0)
+
 #endif
 
 /* Some Solaris platforms are missing isinf(). */
@@ -122,9 +142,11 @@ typedef struct {
     char *char2escape[256]; /* Encoding */
 #endif
     strbuf_t encode_buf;
-#if USE_POSIX_LOCALE
+#if defined(USE_POSIX_USELOCALE)
     locale_t saved_locale;
     locale_t posix_locale;
+#elif defined(USE_POSIX_SETLOCALE)
+    const char *saved_locale;
 #endif
     char number_fmt[8];     /* "%.XXg\0" */
     int current_depth;
@@ -369,7 +391,7 @@ static int json_destroy_config(lua_State *l)
     json_config_t *cfg;
 
     cfg = lua_touserdata(l, 1);
-#ifdef USE_POSIX_LOCALE
+#ifdef USE_POSIX_USELOCALE
     if (cfg->posix_locale)
         freelocale(cfg->posix_locale);
 #endif
@@ -394,7 +416,7 @@ static void json_create_config(lua_State *l)
     lua_setmetatable(l, -2);
 
     strbuf_init(&cfg->encode_buf, 0);
-#if USE_POSIX_LOCALE
+#ifdef USE_POSIX_USELOCALE
     cfg->saved_locale = NULL;
     /* Must not lua_error() before cfg->posix_locale has been initialised */
     cfg->posix_locale = newlocale(LC_ALL_MASK, "C", NULL);