Merged Thomas changes related to version macros.

libisofs/libisofs.h

@@ -8,55 +8,6 @@
 #ifndef LIBISO_LIBISOFS_H_
 #define LIBISO_LIBISOFS_H_
 
-/** 
- * These three release version numbers tell the revision of this header file
- * and of the API it describes. They are memorized by applications at compile 
- * time.
- * 
- * Before usage on your code, please read the usage discussion below.
- */
-#define libisofs_header_version_major  0
-#define libisofs_header_version_minor  6
-#define libisofs_header_version_micro  1
-
-/** 
- * Usage discussion:
- * 
- * Some developers of the libburnia project have differing opinions how to 
- * ensure the compatibility of libaries and applications.
- * 
- * It is about whether to use at compile time and at runtime the version 
- * numbers provided here. Thomas Schmitt advises to use them. Vreixo Formoso 
- * advises to use other means.
- * 
- * At compile time:
- * 
- * Vreixo Formoso advises to leave proper version matching to properly 
- * programmed checks in the the application's build system, which will 
- * eventually refuse compilation.
- * 
- * Thomas Schmitt advises to use the macros defined here for comparison with 
- * the application's requirements of library revisions and to eventually 
- * break compilation.
- * 
- * Both advises are combinable. I.e. be master of your build system and have 
- * #if checks in the source code of your application, nevertheless.
- * 
- * At runtime (via iso_lib_is_compatible()):
- * 
- * Vreixo Formoso advises to compare the application's requirements of 
- * library revisions with the runtime library. This is to allow runtime 
- * libraries which are young enough for the application but too old for
- * the lib*.h files seen at compile time.
- * 
- * Thomas Schmitt advises to compare the header revisions defined here with 
- * the runtime library. This is to enforce a strictly monotonous chain of 
- * revisions from app to header to library, at the cost of excluding some older
- * libraries.
- * 
- * These two advises are mutually exclusive.
- */
-
 #include <sys/stat.h>
 #include <stdint.h>
 
@@ -691,19 +642,82 @@ void iso_finish();
  */
 int iso_image_new(const char *name, IsoImage **image);
 
+
+/** 
+ * The following two functions three macros are utilities to help ensuring
+ * version match of application, compile time header, and runtime library.
+ */
 /**
- * Get version of the libisofs library.
+ * Get version of the libisofs library at runtime.
  */
 void iso_lib_version(int *major, int *minor, int *micro);
 
 /**
- * Check if the library is ABI compatible with the given version.
+ * Check at runtime if the library is ABI compatible with the given version.
  * 
  * @return 
  *      1 lib is compatible, 0 is not.
  */
 int iso_lib_is_compatible(int major, int minor, int micro);
 
+
+/** 
+ * These three release version numbers tell the revision of this header file
+ * and of the API it describes. They are memorized by applications at
+ * compile time.
+ * They must show the same values as these symbols in ./configure.ac
+ *     LIBISOFS_MAJOR_VERSION=...
+ *     LIBISOFS_MINOR_VERSION=...
+ *     LIBISOFS_MICRO_VERSION=...
+ * Note to anybody who does own work inside libisofs:
+ * Any change of configure.ac or libisofs.h has to keep up this equality !
+ * 
+ * Before usage of these macros on your code, please read the usage discussion 
+ * below.
+ */
+#define iso_lib_header_version_major  0
+#define iso_lib_header_version_minor  6
+#define iso_lib_header_version_micro  1
+
+/** 
+ * Usage discussion:
+ * 
+ * Some developers of the libburnia project have differing opinions how to 
+ * ensure the compatibility of libaries and applications.
+ * 
+ * It is about whether to use at compile time and at runtime the version 
+ * numbers provided here. Thomas Schmitt advises to use them. Vreixo Formoso 
+ * advises to use other means.
+ * 
+ * At compile time:
+ * 
+ * Vreixo Formoso advises to leave proper version matching to properly 
+ * programmed checks in the the application's build system, which will 
+ * eventually refuse compilation.
+ * 
+ * Thomas Schmitt advises to use the macros defined here for comparison with 
+ * the application's requirements of library revisions and to eventually 
+ * break compilation.
+ * 
+ * Both advises are combinable. I.e. be master of your build system and have 
+ * #if checks in the source code of your application, nevertheless.
+ * 
+ * At runtime (via iso_lib_is_compatible()):
+ * 
+ * Vreixo Formoso advises to compare the application's requirements of 
+ * library revisions with the runtime library. This is to allow runtime 
+ * libraries which are young enough for the application but too old for
+ * the lib*.h files seen at compile time.
+ * 
+ * Thomas Schmitt advises to compare the header revisions defined here with 
+ * the runtime library. This is to enforce a strictly monotonous chain of 
+ * revisions from app to header to library, at the cost of excluding some older
+ * libraries.
+ * 
+ * These two advises are mutually exclusive.
+ */
+
+
 /**
  * Creates an IsoWriteOpts for writing an image. You should set the options
  * desired with the correspondent setters.