Re: GUC values - recommended way to declare the C variables?

+#ifdef USE_ASSERT_CHECKING
+ sanity_check_GUC_C_var(hentry->gucvar);
+#endif

=> You can conditionally define that as an empty function so #ifdefs
aren't needed in the caller:

void sanity_check_GUC_C_var()
{
#ifdef USE_ASSERT_CHECKING
...
#endif
}

+ /* Skip checking for dynamic (compiler-dependent) GUCs. */

=> This should say that the GUC's default is determined at compile-time.

But actually, I don't think you should use my patch. You needed to
exclude update_process_title:

src/backend/utils/misc/ps_status.c:bool update_process_title = true;
...
src/backend/utils/misc/guc_tables.c-#ifdef WIN32
src/backend/utils/misc/guc_tables.c- false,
src/backend/utils/misc/guc_tables.c-#else
src/backend/utils/misc/guc_tables.c- true,
src/backend/utils/misc/guc_tables.c-#endif
src/backend/utils/misc/guc_tables.c- NULL, NULL, NULL

My patch would also exclude the 16 other GUCs with compile-time defaults
from your check. It'd be better not to exclude them; I think the right
solution is to change the C variable initialization to a compile-time
constant:

#ifdef WIN32
bool update_process_title = false;
#else
bool update_process_title = true;
#endif

Or something more indirect like:

#ifdef WIN32
#define DEFAULT_PROCESS_TITLE false
#else
#define DEFAULT_PROCESS_TITLE true
#endif

bool update_process_title = DEFAULT_PROCESS_TITLE;

I suspect there's not many GUCs that would need to change - this might
be the only one. If this GUC were defined in the inverse (bool
skip_process_title), it wouldn't need special help, either.

--
Justin