=for apidoc Am|char*|SvPVX|SV* sv
Returns a pointer to the physical string in the SV. The SV must contain a
-string.
+string. Prior to 5.9.3 it is not safe to execute this macro unless the SV's
+type >= SVt_PV.
This is also used to store the name of an autoloaded subroutine in an XS
AUTOLOAD routine. See L<perlguts/Autoloading with XSUBs>.