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Add a README and Makefile recipe for Gen_dummy_probes.pl

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Discussion: https://postgr.es/m/20210506035602.3akutfvvojngj3nb@alap3.anarazel.de
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Andrew Dunstan 2021-05-07 14:27:18 -04:00
parent 9f989a8581
commit 8292c0675a
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2 changed files with 35 additions and 0 deletions
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10
src/backend/utils/Makefile
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@ -88,6 +88,16 @@ $(top_builddir)/src/include/utils/probes.h: probes.h
cd '$(dir $@)' && rm -f $(notdir $@) && \
$(LN_S) "../../../$(subdir)/probes.h" .
# Recipe for rebuilding the Perl version of Gen_dummy_probes
# Nothing depends on it, so it will never be called unless explicitly requested
# The last two lines of the recipe format the script according to our
# standard and put back some blank lines for improved readability.
Gen_dummy_probes.pl: Gen_dummy_probes.sed
perl -ni -e ' print; exit if /^\$$0/;' $@
s2p -f $< | sed -e 1,4d -e '/# #/d' -e '$$d' >> $@
perltidy --profile=../../tools/pgindent/perltidyrc $@
perl -pi -e '!$$lb && ( /^\t+#/ || /^# prototypes/ ) && print qq{\n};'\
-e '$$lb = m/^\n/; ' $@
.PHONY: install-data
install-data: errcodes.txt installdirs

25
src/backend/utils/README.Gen_dummy_probes Normal file
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@ -0,0 +1,25 @@
# 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`