tests/test_cext0: Add.

Add some testing of the cext macros.  This is incomplete, but a start to
at least test some of it.

Author: lorinder

test/CMakeLists.txt

@@ -2,6 +2,7 @@ set(tests_c
 	arr_test0.c
 	arr_test1.c
 	clopts_test0.c
+	cext_test0.c
 	err_test0.c
 	err_test1.c
 	fmt_test0.c
@@ -55,6 +56,14 @@ foreach(fn
 	)
 endforeach()
 
+add_executable(cext_test0_c23 cext_test0.c)
+target_link_libraries(cext_test0_c23 csnip)
+set_property(TARGET cext_test0_c23 PROPERTY C_STANDARD 23)
+add_test(
+	NAME cext_test0_c23
+	COMMAND $<TARGET_FILE:cext_test0_c23>
+)
+
 set_property(TARGET clopts_test0 PROPERTY C_STANDARD 11)
 set_property(TARGET limits_test PROPERTY C_STANDARD 11)
 set_property(TARGET runif_getf_test PROPERTY C_STANDARD 11)

test/cext_test0.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+
+#include <csnip/cext.h>
+
+csnip_cext_unused static int f(void)
+{
+	return 0;
+}
+
+csnip_cext_export void g(void);
+
+void g(void)
+{
+	puts("Exported function");
+}
+
+int main(void)
+{
+	puts("No runtime tests here -> pass.");
+	return 0;
+}