binary compatibility check [was Re: [AD] Indexed datafiles]

[Elias Pschernig <elias@xxxxxxxxxx>]

Hm, I just tried to get install_allegro to fail, and apparently the
current version crashes in get_config_text whenever it detects a
mismatch, since Allegro wasn't installed.

The attached revised version of the patch attemps to correct this by
simply installing it first, and do the compatibility check afterwards.
This also means that allegro_message will work and therefore give a
meaningful popup message to users.

-- 
Elias Pschernig

Index: include/allegro/system.h
===================================================================
--- include/allegro/system.h	(revision 5659)
+++ include/allegro/system.h	(working copy)
@@ -71,25 +71,40 @@
 #define SYSTEM_AUTODETECT  0
 #define SYSTEM_NONE        AL_ID('N','O','N','E')
 
-#if (ALLEGRO_SUB_VERSION&1)
 #define MAKE_VERSION(a, b, c) (((a)<<16)|((b)<<8)|(c))
-#else
-#define MAKE_VERSION(a, b, c) (((a)<<16)|((b)<<8))
-#endif
 
 AL_FUNC(int, _get_allegro_version, (void));
 AL_FUNC(int, _install_allegro, (int system_id, int *errno_ptr, AL_METHOD(int, atexit_ptr, (AL_METHOD(void, func, (void))))));
 
-AL_INLINE(int, install_allegro, (int system_id, int *errno_ptr, AL_METHOD(int, atexit_ptr, (AL_METHOD(void, func, (void))))),
+AL_INLINE(int, install_allegro, (int system_id, int *errno_ptr,
+   AL_METHOD(int, atexit_ptr, (AL_METHOD(void, func, (void))))),
 {
-   if (MAKE_VERSION(ALLEGRO_VERSION, ALLEGRO_SUB_VERSION, ALLEGRO_WIP_VERSION) !=
-       _get_allegro_version()) {
-      ustrzcpy(allegro_error, ALLEGRO_ERROR_SIZE, get_config_text("Library version mismatch"));
+   int r = _install_allegro(system_id, errno_ptr, atexit_ptr);
+   int dll_v = _get_allegro_version(); /* This comes from the DLL. */
+
+#if ((ALLEGRO_SUB_VERSION&1) == 0)
+   int dll_wip = dll_v & 255;
+   int dll_ver = dll_v & ~255;
+
+   /* Check that the x.y versions match (eg. 4.2 = 4.2) and that the DLL WIP
+    * version is at least as new as the headers we were compiled with */
+   if ((dll_ver != MAKE_VERSION(ALLEGRO_VERSION, ALLEGRO_SUB_VERSION, 0)) ||
+       (dll_wip < ALLEGRO_WIP_VERSION)) {
+#else
+   /* Enforce strict header x.y.z == lib x.y.z for WIP branches */
+   if (dll_v != MAKE_VERSION(ALLEGRO_VERSION, ALLEGRO_SUB_VERSION, 
+      ALLEGRO_WIP_VERSION)) {
+#endif
+      uszprintf(allegro_error, ALLEGRO_ERROR_SIZE, get_config_text(
+         "The detected dynamic Allegro library (%d.%d.%d) is "
+         "not compatible with this program (%d.%d.%d)."),
+         dll_ver >> 16, (dll_ver >> 8) & 255, dll_wip,
+         ALLEGRO_VERSION, ALLEGRO_SUB_VERSION, ALLEGRO_WIP_VERSION);
       return !0;
    }
+   return r;
+})
 
-   return _install_allegro(system_id, errno_ptr, atexit_ptr);
-})
 #define allegro_init()  install_allegro(SYSTEM_AUTODETECT, &errno, (int (*)(void (*)(void)))atexit)
 AL_FUNC(void, allegro_exit, (void));