Perl likes to redefine the _() macro:
#ifdef CAN_PROTOTYPE
#define _(args) args
#else ...
There was lots not to like about the way we dealt with this before:
1. Instead of taking care of the conflict centrally in plperl.h, we
expected every one of its ever-growing number of includers to do so.
This is duplicative and error-prone in itself, plus it means that
plperl.h fails to meet the expectation of being compilable standalone,
resulting in macro-redefinition warnings in cpluspluscheck.
2. We left _() with its Perl definition, meaning that if someone tried
to use it in any Perl-related extension, it would silently fail to
provide run-time translation. I don't see any live bugs of this ilk,
but it's clearly a hard-to-notice bug waiting to happen.
So fix that by centralizing the cleanup logic, making it match what
we're already doing for other macro conflicts with Perl. Since we only
expect plperl.h to be included by extensions not core code, we should
redefine _() as dgettext() not gettext().
The PostgreSQL contrib tree
---------------------------
This subtree contains porting tools, analysis utilities, and plug-in
features that are not part of the core PostgreSQL system, mainly
because they address a limited audience or are too experimental to be
part of the main source tree. This does not preclude their
usefulness.
User documentation for each module appears in the main SGML
documentation.
When building from the source distribution, these modules are not
built automatically, unless you build the "world" target. You can
also build and install them all by running "make all" and "make
install" in this directory; or to build and install just one selected
module, do the same in that module's subdirectory.
Some directories supply new user-defined functions, operators, or
types. To make use of one of these modules, after you have installed
the code you need to register the new SQL objects in the database
system by executing a CREATE EXTENSION command. In a fresh database,
you can simply do
CREATE EXTENSION module_name;
See the PostgreSQL documentation for more information about this
procedure.