Add API version checking for modules.

Checking now actively implemented for dynamic modules
in a fully backwards compatible way.

src/core/capi.c

@@ -26,14 +26,15 @@
 #include "fiber.h"
 #endif
 
-static JanetBuildConfig *api_build_config = &(JanetBuildConfig) {
-    .api_version = JANET_API_VERSION,
-    .single_threaded = JANET_SINGLE_THREADED_BIT,
-    .nanbox = JANET_NANBOX_BIT
+static const JanetBuildConfig api_build_config = (JanetBuildConfig) {
+    JANET_VERSION_MAJOR,
+    JANET_VERSION_MINOR,
+    JANET_VERSION_PATCH,
+    JANET_CURRENT_CONFIG_BITS
 };
 
-const JanetBuildConfig *janet_build_config() {
-    return api_build_config;
+const JanetBuildConfig *janet_config_host(void) {
+    return &api_build_config;
 }
 
 void janet_panicv(Janet message) {

src/core/corelib.c

@@ -63,7 +63,30 @@ JanetModule janet_native(const char *name, const uint8_t **error) {
     }
     init = (JanetModule) symbol_clib(lib, "_janet_init");
     if (!init) {
-        *error = janet_cstring("could not find _janet_init symbol");
+        *error = janet_cstring("could not find the _janet_init symbol");
+        return NULL;
+    }
+    JanetBuildConfig(*modconf_getter)(void) = symbol_clib(lib, "_janet_mod_config");
+    if (!modconf_getter) {
+        *error = janet_cstring("could not find the _janet_mod_config symbol");
+        return NULL;
+    }
+    JanetBuildConfig modconf = modconf_getter();
+    JanetBuildConfig host = janet_config_current();
+    if (host.major != modconf.major ||
+            host.minor < modconf.minor ||
+            host.bits != modconf.bits) {
+        char errbuf[128];
+        sprintf(errbuf, "config mismatch - host %d.%.d.%d(%.4x) vs. module %d.%d.%d(%.4x)",
+                host.major,
+                host.minor,
+                host.patch,
+                host.bits,
+                modconf.major,
+                modconf.minor,
+                modconf.patch,
+                modconf.bits);
+        *error = janet_cstring(errbuf);
         return NULL;
     }
     return init;
@@ -830,6 +853,9 @@ JanetTable *janet_core_env(JanetTable *replacements) {
               JDOC("The version number of the running janet program."));
     janet_def(env, "janet/build", janet_cstringv(JANET_BUILD),
               JDOC("The build identifier of the running janet program."));
+    janet_def(env, "janet/config-bits", janet_wrap_integer(JANET_CURRENT_CONFIG_BITS),
+              JDOC("The flag set of config options from janetconf.h which is used to check "
+                   "if native modules are compatible with the host program."));
 
     /* Allow references to the environment */
     janet_def(env, "_env", janet_wrap_table(env), JDOC("The environment table for the current scope."));

src/include/janet.h

@@ -31,8 +31,6 @@ extern "C" {
 
 #include "janetconf.h"
 
-#define JANET_API_VERSION 1
-
 #ifndef JANET_VERSION
 #define JANET_VERSION "latest"
 #endif
@@ -186,26 +184,38 @@ extern "C" {
 #endif
 #endif
 
-
 /* Runtime config constants */
 #ifdef JANET_NO_NANBOX
 #define JANET_NANBOX_BIT 0
 #else
-#define JANET_NANBOX_BIT 1
+#define JANET_NANBOX_BIT 0x1
 #endif
 
 #ifdef JANET_SINGLE_THREADED
-#define JANET_SINGLE_THREADED_BIT 1
+#define JANET_SINGLE_THREADED_BIT 0x2
 #else
 #define JANET_SINGLE_THREADED_BIT 0
 #endif
 
+#define JANET_CURRENT_CONFIG_BITS \
+    (JANET_SINGLE_THREADED_BIT | \
+     JANET_NANBOX_BIT)
+
+/* Represents the settings used to compile Janet, as well as the version */
 typedef struct {
-    int api_version;
-    int single_threaded : 1;
-    int nanbox : 1;
+    unsigned major;
+    unsigned minor;
+    unsigned patch;
+    unsigned bits;
 } JanetBuildConfig;
 
+/* Get config of current compilation unit. */
+#define janet_config_current() ((JanetBuildConfig){ \
+    JANET_VERSION_MAJOR, \
+    JANET_VERSION_MINOR, \
+    JANET_VERSION_PATCH, \
+    JANET_CURRENT_CONFIG_BITS })
+
 /***** END SECTION CONFIG *****/
 
 /***** START SECTION TYPES *****/
@@ -1276,15 +1286,11 @@ JANET_API void janet_register(const char *name, JanetCFunction cfun);
 
 /* New C API */
 
-#define JANET_MODULE_ENTRY JANET_API void _janet_init
-
-JANET_API int janet_api_version();
-JANET_API const JanetBuildConfig *janet_build_config();
-
-#define janet_api_compatible() \
-  ((janet_api_build_config()->api_version == JANET_API_VERSION) \
-   && (janet_api_build_config()->nanbox == JANET_NANBOX_BIT) \
-   && (janet_api_build_config()->single_threaded == JANET_SINGLE_THREADED_BIT))
+#define JANET_MODULE_ENTRY \
+    JANET_API JanetBuildConfig _janet_mod_config(void) { \
+        return janet_config_current(); \
+    } \
+    JANET_API void _janet_init
 
 JANET_API void janet_panicv(Janet message);
 JANET_API void janet_panic(const char *message);

src/include/janetconf.h

@@ -25,7 +25,11 @@
 #ifndef JANETCONF_H
 #define JANETCONF_H
 
-#define JANET_VERSION "0.6.0"
+#define JANET_VERSION_MAJOR 0
+#define JANET_VERSION_MINOR 6
+#define JANET_VERSION_PATCH 0
+#define JANET_VERSION_EXTRA "-dev"
+#define JANET_VERSION "0.6.0-dev"
 
 /* #define JANET_BUILD "local" */