vips_init() does ABI checking

just checks sizeof(VipsObject) for now

ChangeLog

@@ -1,5 +1,7 @@
 19/10/13 started 7.37.0
-- redone im_rotate_*mask45(), im_gauss_*mask*(), im_log_*mask*() as classes
+- redone im_rotate_*mask45(), im_gauss_*mask*(), im_log_*mask() as classes
+- vips_init() now does some ABI compat checking, though this change requires
+  an ABI break
 
 18/10/13	started 7.36.3
 - fix compiler warnings in ubuntu 13.10

TODO

@@ -1,15 +1,3 @@
-- do log mask generation, common base class with the gauss mask builder?
-
-- make vips_init() into a macro, check sizes of important structs against size
-  at library compile time
-
-  add a new API call like vips__get_sizeof_image() which returns
-  sizeof(VipsImage) from library compile time, compare that to the application
-  compile-time value
-
-  vips_init() macro then passes control on to vips__init() for real startup
-
-  breaks binary API sadly
 
 - do conv and morph quickly as simple wrappers over the vips7 operations
 

libvips/deprecated/vips7compat.c

@@ -50,6 +50,12 @@
 #include <vips/vector.h>
 #include <vips/transform.h>
 
+int 
+im_init_world( const char *argv0 )
+{
+	return( vips_init( argv0 ) ); 
+}
+
 VipsImage *
 im_open( const char *filename, const char *mode )
 {

libvips/include/vips/private.h

@@ -56,6 +56,11 @@ extern "C" {
  */
 #define VIPS_SIZEOF_HEADER (64)
 
+/* Startup plus ABI check.
+ */
+int vips__init( const char *argv0 );
+size_t vips__get_sizeof_vipsobject( void );
+
 /* What we track for each mmap window. Have a list of these on an openin
  * VipsImage.
  */

libvips/include/vips/vips.h

@@ -149,8 +149,20 @@ extern "C" {
 #include <vips/almostdeprecated.h>
 #include <vips/dispatch.h>
 
+#define vips_init( ARGV0 ) \
+	(sizeof( VipsObject ) != vips__get_sizeof_vipsobject() ? ( \
+		vips_info( "vips_init", "%s", _( "ABI mismatch" ) ), \
+		vips_info( "vips_init", \
+			_( "library has sizeof(VipsObject) == %zd" ), \
+			vips__get_sizeof_vipsobject() ), \
+		vips_info( "vips_init", \
+			_( "application has sizeof(VipsObject) == %zd" ), \
+			sizeof( VipsObject() ) ), \
+		vips_error( "vips_init", "%s", _( "ABI mismatch" ) ), \
+		-1 ) : \
+		vips__init( ARGV0 ))
+
 const char *vips_get_argv0( void );
-int vips_init( const char *argv0 );
 void vips_check_init( void );
 void vips_shutdown( void );
 GOptionGroup *vips_get_option_group( void );

libvips/include/vips/vips7compat.h

@@ -203,7 +203,6 @@ extern "C" {
 #define im_get_argv0 vips_get_argv0
 #define im_version_string vips_version_string
 #define im_version vips_version
-#define im_init_world vips_init
 #define im_get_option_group vips_get_option_group
 #define im_guess_prefix vips_guess_prefix
 #define im_guess_libdir vips_guess_libdir
@@ -586,6 +585,8 @@ size_t im_ref_string_get_length( const GValue *value );
 #define im_concurrency_set vips_concurrency_set
 #define im_concurrency_get vips_concurrency_get
 
+int im_init_world( const char *argv0 ); 
+
 int im_add( VipsImage *in1, VipsImage *in2, VipsImage *out );
 int im_subtract( VipsImage *in1, VipsImage *in2, VipsImage *out );
 int im_multiply( VipsImage *in1, VipsImage *in2, VipsImage *out );

libvips/iofuncs/init.c

@@ -140,7 +140,7 @@ vips_get_argv0( void )
  *     </para>
  *   </listitem>
  *   <listitem> 
- *     <para>loads any plugins from $libdir/vips-x.y, where x and y are the
+ *     <para>loads any plugins from $libdir/vips-x.y/, where x and y are the
  *     major and minor version numbers for this VIPS.
  *     </para>
  *   </listitem>
@@ -165,8 +165,13 @@ vips_get_argv0( void )
  *
  * Returns: 0 on success, -1 otherwise
  */
+
+/* vips_init() is actually a macro which checks library and application
+ * compatibility before calling vips__init().
+ */
+
 int
-vips_init( const char *argv0 )
+vips__init( const char *argv0 )
 {
 	extern GType vips_system_get_type( void );
 
@@ -299,6 +304,20 @@ vips_init( const char *argv0 )
 	return( 0 );
 }
 
+/* Return the sizeof() various important data structures. These are checked
+ * against the headers used to build our caller by vips_init().
+ *
+ * We allow direct access to members of VipsImage and VipsRegion (mostly for
+ * reasons of history), so any change to a superclass of either of these
+ * objects will break our ABI.
+ */
+
+size_t
+vips__get_sizeof_vipsobject( void )
+{
+	return( sizeof( VipsObject ) ); 
+}
+
 /* Call this before vips stuff that uses stuff we need to have inited.
  */
 void