shared/verbs: allow multiple verbs to be handled by a single function

With the uintptr_t data parameter, it is actually quite nice to have
VERB(do_impl, "name-a", …)
VERB(do_impl, "name-b", …)
int do_impl(…) { … }

To make this work, the do_impl_data struct needs to have a unique name and
we also need to suppress the warning about the forward declaration for
do_impl being repeated. I think it's fine to suppress the warning, it's
not needed for anything. If somebody declares the function with the same
name by mistake, the implementations are going to conflict too.

src/fundamental/macro-fundamental.h

@@ -143,6 +143,7 @@
 
 #define XCONCATENATE(x, y) x ## y
 #define CONCATENATE(x, y) XCONCATENATE(x, y)
+#define CONCATENATE3(x, y, z) CONCATENATE(x, CONCATENATE(y, z))
 
 #define assert_cc(expr) _Static_assert(expr, #expr)
 

src/shared/verbs.h

@@ -21,13 +21,15 @@ typedef struct {
 } Verb;
 
 #define VERB_FULL(d, v, a, amin, amax, f, dat, h)                       \
+        DISABLE_WARNING_REDUNDANT_DECLS                                 \
         static int d(int, char**, uintptr_t, void*);                    \
+        REENABLE_WARNING                                                \
         _section_("SYSTEMD_VERBS")                                      \
         _alignptr_                                                      \
         _used_                                                          \
         _retain_                                                        \
         _variable_no_sanitize_address_                                  \
-        static const Verb CONCATENATE(d, _data) = {                     \
+        static const Verb CONCATENATE3(d, _data_, __COUNTER__) = {      \
                 .verb = v,                                              \
                 .min_args = amin,                                       \
                 .max_args = amax,                                       \