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postgres/src/backend/utils
Tom Lane 0a20ff54f5 Split up guc.c for better build speed and ease of maintenance.
guc.c has grown to be one of our largest .c files, making it
a bottleneck for compilation.  It's also acquired a bunch of
knowledge that'd be better kept elsewhere, because of our not
very good habit of putting variable-specific check hooks here.
Hence, split it up along these lines:

* guc.c itself retains just the core GUC housekeeping mechanisms.
* New file guc_funcs.c contains the SET/SHOW interfaces and some
  SQL-accessible functions for GUC manipulation.
* New file guc_tables.c contains the data arrays that define the
  built-in GUC variables, along with some already-exported constant
  tables.
* GUC check/assign/show hook functions are moved to the variable's
  home module, whenever that's clearly identifiable.  A few hard-
  to-classify hooks ended up in commands/variable.c, which was
  already a home for miscellaneous GUC hook functions.

To avoid cluttering a lot more header files with #include "guc.h",
I also invented a new header file utils/guc_hooks.h and put all
the GUC hook functions' declarations there, regardless of their
originating module.  That allowed removal of #include "guc.h"
from some existing headers.  The fallout from that (hopefully
all caught here) demonstrates clearly why such inclusions are
best minimized: there are a lot of files that, for example,
were getting array.h at two or more levels of remove, despite
not having any connection at all to GUCs in themselves.

There is some very minor code beautification here, such as
renaming a couple of inconsistently-named hook functions
and improving some comments.  But mostly this just moves
code from point A to point B and deals with the ensuing
needs for #include adjustments and exporting a few functions
that previously weren't exported.

Patch by me, per a suggestion from Andres Freund; thanks also
to Michael Paquier for the idea to invent guc_funcs.c.

Discussion: https://postgr.es/m/587607.1662836699@sss.pgh.pa.us
2022-09-13 11:11:45 -04:00
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# Generating dummy probes

If Postgres isn't configured with dtrace enabled, we need to generate
dummy probes for the entries in probes.d, that do nothing.

This is accomplished in Unix via the sed script `Gen_dummy_probes.sed`. We
used to use this in MSVC builds using the perl utility `psed`, which mimicked
sed. However, that utility disappeared from Windows perl distributions and so
we converted the sed script to a perl script to be used in MSVC builds.

We still keep the sed script as the authoritative source for generating
these dummy probes because except on Windows perl is not a hard requirement
when building from a tarball.

So, if you need to change the way dummy probes are generated, first change
the sed script, and when it's working generate the perl script. This can
be accomplished by using the perl utility s2p.

s2p is no longer part of the perl core, so it might not be on your system,
but it is available on CPAN and also in many package systems. e.g.
on Fedora it can be installed using `cpan App::s2p` or
`dnf install perl-App-s2p`.

The Makefile contains a recipe for regenerating Gen_dummy_probes.pl, so all
you need to do is once you have s2p installed is `make Gen_dummy_probes.pl`
Note that in a VPATH build this will generate the file in the vpath tree,
not the source tree.