scanner: Guard interface declarations

This allows to include client and server headers in the same file
fixing warnings like

In file included from ../subprojects/wlroots/include/wlr/types/wlr_layer_shell_v1.h:16,
                 from ../src/desktop.h:16,
                 from ../src/server.h:13,
                 from ../tests/testlib.c:8:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-protocol.h:80:34: warning: redundant redeclaration of ‘zwlr_layer_shell_v1_interface’ [-Wredundant-decls]
   80 | extern const struct wl_interface zwlr_layer_shell_v1_interface;
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../tests/testlib.h:8,
                 from ../tests/testlib.c:7:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-client-protocol.h:77:34: note: previous declaration of ‘zwlr_layer_shell_v1_interface’ was here
   77 | extern const struct wl_interface zwlr_layer_shell_v1_interface;
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../subprojects/wlroots/include/wlr/types/wlr_layer_shell_v1.h:16,
                 from ../src/desktop.h:16,
                 from ../src/server.h:13,
                 from ../tests/testlib.c:8:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-protocol.h:106:34: warning: redundant redeclaration of ‘zwlr_layer_surface_v1_interface’ [-Wredundant-decls]
  106 | extern const struct wl_interface zwlr_layer_surface_v1_interface;
      |                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../tests/testlib.h:8,
                 from ../tests/testlib.c:7:
tests/59830eb@@footest@sta/wlr-layer-shell-unstable-v1-client-protocol.h:103:34: note: previous declaration of ‘zwlr_layer_surface_v1_interface’ was here
  103 | extern const struct wl_interface zwlr_layer_surface_v1_interface;

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Closes: #158

1 files changed, 3 insertions, 0 deletions

diff --git a/src/scanner.c b/src/scanner.c
index b470c91..36ac905 100644
--- a/src/scanner.c
+++ b/src/scanner.c
@@ -1636,6 +1636,8 @@ emit_header(struct protocol *protocol, enum side side)
 	printf("\n");
 
 	wl_list_for_each(i, &protocol->interface_list, link) {
+		printf("#ifndef %s_INTERFACE\n", i->uppercase_name);
+		printf("#define %s_INTERFACE\n", i->uppercase_name);
 		printf("/**\n"
 		       " * @page page_iface_%s %s\n",
 		       i->name, i->name);
@@ -1656,6 +1658,7 @@ emit_header(struct protocol *protocol, enum side side)
 		printf(" */\n");
 		printf("extern const struct wl_interface "
 		       "%s_interface;\n", i->name);
+		printf("#endif\n");
 	}
 
 	printf("\n");