Add C++ header guards

And a basic build test for C++ to make sure including the headers doesn't
completely fail.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

meson.build

@@ -276,6 +276,14 @@ executable('test-build-libreis',
 	   c_args : ['-Werror', '-DINCLUDE_LIBREIS=1'],
 	   install : false)
 
+if add_languages('cpp', required: false)
+	executable('test-build-cxx',
+		       'test/buildtest.cc',
+               dependencies: [dep_libei, dep_libeis],
+               include_directories: 'src',
+               install: false)
+endif
+
 configure_file(output: 'config.h', configuration: config_h)
 
 if get_option('documentation')

src/libei.h

@@ -23,6 +23,10 @@
 
 #pragma once
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stdbool.h>
 #include <stdint.h>
 #include <stddef.h>
@@ -881,3 +885,7 @@ ei_event_get_time(struct ei_event *event);
 /**
  * @}
  */
+
+#ifdef __cplusplus
+}
+#endif

src/libeis.h

@@ -24,6 +24,10 @@
 
 #pragma once
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 #include <stddef.h>
 #include <stdbool.h>
 #include <stdint.h>
@@ -597,3 +601,7 @@ eis_event_touch_get_y(struct eis_event *event);
 /**
  * @}
  */
+
+#ifdef __cplusplus
+}
+#endif

test/buildtest.cc

@@ -0,0 +1,12 @@
+#include <libei.h>
+#include <libeis.h>
+
+/* This is a build-test only */
+
+using namespace std;
+
+int
+main(void)
+{
+	return 0;
+}