+ * GRAS_DEFINE_TYPE declares some symbols to work, it needs some special
+ * care when used in several files. In such case, you want the regular type
+ * definition in all files, but the gras specific symbol defined in only
+ * one file. For example, consider the following gras project sketch.
+ *
+\verbatim #include <gras.h>
+
+GRAS_DEFINE_TYPE(my_type,struct my_type {
+ int a;
+ int b;
+ double c;
+});
+
+int client(int argc, char *argv[]) {
+ ...
+}
+
+int server(int argc, char *argv[]) {
+ ...
+}\endverbatim
+ *
+ * If you want to split this in two files (one for each kind of processes),
+ * you need to put the GRAS_DEFINE_TYPE block in a separate header (so that
+ * each process kind see the associated C type definition). But
+ * then you cannot include this right away in all files because the extra
+ * symbols containing the GRAS definition would be dupplicated.
+ *
+ * You thus have to decide in which C file the symbols will live. In that
+ * file, include the header without restriction:
+ *
+\verbatim #include "my_header.h"
+
+int client(int argc, char *argv[]) {
+ ...
+}\endverbatim
+
+ * And in the other files needing the C definitions without the extra GRAS
+ * symbols, declare the symbol GRAS_DEFINE_TYPE_EXTERN before loading gras.h:
+ *
+\verbatim #define GRAS_DEFINE_TYPE_EXTERN
+#include <gras.h>
+#include "my_header.h"
+
+int server(int argc, char *argv[]) {
+ ...
+}\endverbatim
+
+ *
+ * Sometimes, the situation is even more complicated: There is some shared
+ * messages that you want to see from every file, and some private messages
+ * that you want to be defined only in one C file.
+ * In that case, use the previous trick for common messages, and use
+ * #GRAS_DEFINE_TYPE_LOCAL for the private messages.
+ *
+ * For now, there is no way to have semi-private symbols (for example shared
+ * in all files of a library), sorry. Use functions as interface to your
+ * library instead of publishing directly the messages.