From @gsar

Some compilers (e.g. Borland) emit a "unused type" warning when you declare
a typedef and don't use it.

Perl.c​: In function `XS_DBD__Perl__dr_discon_all_'​:
Perl.c​:32​: warning​: unused variable `Perl___notused'

I recall the extern is much safer, because there are compilers
out there that would croak with a "duplicate typedef" when they
see​:

  dNOOP; /* say from dTHR; */
  dNOOP; /* say from dTHX; */

Feel free to send a patch for the specific compiler in question,
unless someone can think of some other way to get a dNOOP without
these problems.

Sarathy
gsar@​activestate.com

From [Unknown Contact. See original ticket]

dupe