Rework lwlocknames.txt to become lwlocklist.h

This way, we can fold the list of lock names to occur in
BuiltinTrancheNames instead of having its own separate array.  This
saves two lines of code in GetLWTrancheName and some space in
BuiltinTrancheNames, as foreseen in commit 74a7306, as well as
removing the need for a separate lwlocknames.c file.

We still have to build lwlocknames.h using Perl code, which initially I
wanted to avoid, but it gives us the chance to cross-check
wait_event_names.txt.

Discussion: https://postgr.es/m/202401231025.gbv4nnte5fmm@alvherre.pgsql

Author: alvherre

src/backend/Makefile

@@ -110,8 +110,8 @@ $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 parser/gram.h: parser/gram.y
 	$(MAKE) -C parser gram.h
 
-storage/lmgr/lwlocknames.h: storage/lmgr/generate-lwlocknames.pl storage/lmgr/lwlocknames.txt utils/activity/wait_event_names.txt
-	$(MAKE) -C storage/lmgr lwlocknames.h lwlocknames.c
+storage/lmgr/lwlocknames.h: storage/lmgr/generate-lwlocknames.pl ../include/storage/lwlocklist.h utils/activity/wait_event_names.txt
+	$(MAKE) -C storage/lmgr lwlocknames.h
 
 utils/activity/wait_event_types.h: utils/activity/generate-wait_event_types.pl utils/activity/wait_event_names.txt
 	$(MAKE) -C utils/activity wait_event_types.h pgstat_wait_event.c wait_event_funcs_data.c

src/backend/storage/lmgr/.gitignore

@@ -1,3 +1,2 @@
-/lwlocknames.c
 /lwlocknames.h
 /s_lock_test

src/backend/storage/lmgr/Makefile

@@ -18,7 +18,6 @@ OBJS = \
 	lmgr.o \
 	lock.o \
 	lwlock.o \
-	lwlocknames.o \
 	predicate.o \
 	proc.o \
 	s_lock.o \
@@ -35,16 +34,12 @@ s_lock_test: s_lock.c $(top_builddir)/src/common/libpgcommon.a $(top_builddir)/s
 		$(TASPATH) -L $(top_builddir)/src/common -lpgcommon \
 		-L $(top_builddir)/src/port -lpgport -lm -o s_lock_test
 
-# see notes in src/backend/parser/Makefile
-lwlocknames.c: lwlocknames.h
-	touch $@
-
-lwlocknames.h: $(top_srcdir)/src/backend/storage/lmgr/lwlocknames.txt $(top_srcdir)/src/backend/utils/activity/wait_event_names.txt generate-lwlocknames.pl
+lwlocknames.h: ../../../include/storage/lwlocklist.h ../../utils/activity/wait_event_names.txt generate-lwlocknames.pl
 	$(PERL) $(srcdir)/generate-lwlocknames.pl $^
 
 check: s_lock_test
 	./s_lock_test
 
 clean:
 	rm -f s_lock_test
-	rm -f lwlocknames.h lwlocknames.c
+	rm -f lwlocknames.h

src/backend/storage/lmgr/generate-lwlocknames.pl

@@ -1,6 +1,6 @@
 #!/usr/bin/perl
 #
-# Generate lwlocknames.h and lwlocknames.c from lwlocknames.txt
+# Generate lwlocknames.h from lwlocklist.h
 # Copyright (c) 2000-2024, PostgreSQL Global Development Group
 
 use strict;
@@ -14,26 +14,22 @@
 
 GetOptions('outdir:s' => \$output_path);
 
-open my $lwlocknames, '<', $ARGV[0] or die;
+open my $lwlocklist, '<', $ARGV[0] or die;
 open my $wait_event_names, '<', $ARGV[1] or die;
 
 # Include PID in suffix in case parallel make runs this multiple times.
 my $htmp = "$output_path/lwlocknames.h.tmp$$";
-my $ctmp = "$output_path/lwlocknames.c.tmp$$";
 open my $h, '>', $htmp or die "Could not open $htmp: $!";
-open my $c, '>', $ctmp or die "Could not open $ctmp: $!";
 
 my $autogen =
-  "/* autogenerated from src/backend/storage/lmgr/lwlocknames.txt, do not edit */\n";
+  "/* autogenerated from src/include/storage/lwlocklist.h, do not edit */\n";
 print $h $autogen;
 print $h "/* there is deliberately not an #ifndef LWLOCKNAMES_H here */\n\n";
-print $c $autogen, "\n";
 
-print $c "const char *const IndividualLWLockNames[] = {";
 
 #
 # First, record the predefined LWLocks listed in wait_event_names.txt.  We'll
-# cross-check those with the ones in lwlocknames.txt.
+# cross-check those with the ones in lwlocklist.h.
 #
 my @wait_event_lwlocks;
 my $record_lwlocks = 0;
@@ -61,66 +57,70 @@
 
 	# Record the LWLock.
 	(my $waiteventname, my $waitevendocsentence) = split(/\t/, $_);
-	push(@wait_event_lwlocks, $waiteventname . "Lock");
+	push(@wait_event_lwlocks, $waiteventname);
 }
 
+my $in_comment = 0;
 my $i = 0;
-while (<$lwlocknames>)
+while (<$lwlocklist>)
 {
 	chomp;
 
-	# Skip comments
-	next if /^#/;
+	# Skip single-line C comments and empty lines
+	next if m{^\s*/\*.*\*/$};
 	next if /^\s*$/;
 
-	die "unable to parse lwlocknames.txt"
-	  unless /^(\w+)\s+(\d+)$/;
+	# skip multiline C comments
+	if ($in_comment == 1)
+	{
+		$in_comment = 0 if m{\*/};
+		next;
+	}
+	elsif (m{^\s*/\*})
+	{
+		$in_comment = 1;
+		next;
+	}
 
-	(my $lockname, my $lockidx) = ($1, $2);
+	die "unable to parse lwlocklist.h line \"$_\""
+	  unless /^PG_LWLOCK\((\d+),\s+(\w+)\)$/;
 
-	my $trimmedlockname = $lockname;
-	$trimmedlockname =~ s/Lock$//;
-	die "lock names must end with 'Lock'" if $trimmedlockname eq $lockname;
+	(my $lockidx, my $lockname) = ($1, $2);
 
-	die "lwlocknames.txt not in order" if $lockidx < $lastlockidx;
-	die "lwlocknames.txt has duplicates" if $lockidx == $lastlockidx;
+	die "lwlocklist.h not in order" if $lockidx < $lastlockidx;
+	die "lwlocklist.h has duplicates" if $lockidx == $lastlockidx;
 
-	die "$lockname defined in lwlocknames.txt but missing from "
+	die "$lockname defined in lwlocklist.h but missing from "
 	  . "wait_event_names.txt"
 	  if $i >= scalar @wait_event_lwlocks;
 	die "lists of predefined LWLocks do not match (first mismatch at "
 	  . "$wait_event_lwlocks[$i] in wait_event_names.txt and $lockname in "
-	  . "lwlocknames.txt)"
+	  . "lwlocklist.h)"
 	  if $wait_event_lwlocks[$i] ne $lockname;
 	$i++;
 
 	while ($lastlockidx < $lockidx - 1)
 	{
 		++$lastlockidx;
-		printf $c "%s	\"<unassigned:%d>\"", $continue, $lastlockidx;
 		$continue = ",\n";
 	}
-	printf $c "%s	\"%s\"", $continue, $trimmedlockname;
 	$lastlockidx = $lockidx;
 	$continue = ",\n";
 
-	print $h "#define $lockname (&MainLWLockArray[$lockidx].lock)\n";
+	print $h "#define ${lockname}Lock (&MainLWLockArray[$lockidx].lock)\n";
 }
 
 die
   "$wait_event_lwlocks[$i] defined in wait_event_names.txt but missing from "
-  . "lwlocknames.txt"
+  . "lwlocklist.h"
   if $i < scalar @wait_event_lwlocks;
 
-printf $c "\n};\n";
 print $h "\n";
 printf $h "#define NUM_INDIVIDUAL_LWLOCKS		%s\n", $lastlockidx + 1;
 
 close $h;
-close $c;
 
 rename($htmp, "$output_path/lwlocknames.h")
   || die "rename: $htmp to $output_path/lwlocknames.h: $!";
-rename($ctmp, "$output_path/lwlocknames.c") || die "rename: $ctmp: $!";
 
-close $lwlocknames;
+close $lwlocklist;

src/backend/storage/lmgr/lwlock.c

@@ -112,8 +112,8 @@ StaticAssertDecl(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
  * There are three sorts of LWLock "tranches":
  *
  * 1. The individually-named locks defined in lwlocknames.h each have their
- * own tranche.  The names of these tranches appear in IndividualLWLockNames[]
- * in lwlocknames.c.
+ * own tranche.  We absorb the names of these tranches from there into
+ * BuiltinTrancheNames here.
  *
  * 2. There are some predefined tranches for built-in groups of locks.
  * These are listed in enum BuiltinTrancheIds in lwlock.h, and their names
@@ -126,9 +126,10 @@ StaticAssertDecl(LW_VAL_EXCLUSIVE > (uint32) MAX_BACKENDS,
  * All these names are user-visible as wait event names, so choose with care
  * ... and do not forget to update the documentation's list of wait events.
  */
-extern const char *const IndividualLWLockNames[];	/* in lwlocknames.c */
-
 static const char *const BuiltinTrancheNames[] = {
+#define PG_LWLOCK(id, lockname) [id] = CppAsString(lockname) "Lock",
+#include "storage/lwlocklist.h"
+#undef PG_LWLOCK
 	[LWTRANCHE_XACT_BUFFER] = "XactBuffer",
 	[LWTRANCHE_COMMITTS_BUFFER] = "CommitTsBuffer",
 	[LWTRANCHE_SUBTRANS_BUFFER] = "SubtransBuffer",
@@ -742,11 +743,7 @@ LWLockReportWaitEnd(void)
 static const char *
 GetLWTrancheName(uint16 trancheId)
 {
-	/* Individual LWLock? */
-	if (trancheId < NUM_INDIVIDUAL_LWLOCKS)
-		return IndividualLWLockNames[trancheId];
-
-	/* Built-in tranche? */
+	/* Built-in tranche or individual LWLock? */
 	if (trancheId < LWTRANCHE_FIRST_USER_DEFINED)
 		return BuiltinTrancheNames[trancheId];
 

src/backend/storage/lmgr/lwlocknames.txt

@@ -11,5 +11,3 @@ backend_sources += files(
   's_lock.c',
   'spin.c',
 )
-
-generated_backend_sources += lwlocknames[1]

src/backend/storage/lmgr/meson.build

@@ -280,9 +280,9 @@ Extension	"Waiting in an extension."
 # This class of wait events has its own set of C structure, so these are
 # only used for the documentation.
 #
-# NB: Predefined LWLocks (i.e., those declared in lwlocknames.txt) must be
+# NB: Predefined LWLocks (i.e., those declared in lwlocklist.h) must be
 # listed in the top section of locks and must be listed in the same order as in
-# lwlocknames.txt.
+# lwlocklist.h.
 #
 
 Section: ClassName - WaitEventLWLock
@@ -333,9 +333,9 @@ SerialControl	"Waiting to read or update shared <filename>pg_serial</filename> s
 #
 # END OF PREDEFINED LWLOCKS (DO NOT CHANGE THIS LINE)
 #
-# Predefined LWLocks (i.e., those declared in lwlocknames.txt) must be listed
+# Predefined LWLocks (i.e., those declared in lwlocknames.h) must be listed
 # in the section above and must be listed in the same order as in
-# lwlocknames.txt.  Other LWLocks must be listed in the section below.
+# lwlocknames.h.  Other LWLocks must be listed in the section below.
 #
 
 XactBuffer	"Waiting for I/O on a transaction status SLRU buffer."

src/backend/utils/activity/wait_event_names.txt

@@ -19,6 +19,7 @@
 #endif
 
 #include "port/atomics.h"
+#include "storage/lwlocknames.h"
 #include "storage/proclist_types.h"
 
 struct PGPROC;
@@ -82,9 +83,6 @@ typedef struct NamedLWLockTranche
 extern PGDLLIMPORT NamedLWLockTranche *NamedLWLockTrancheArray;
 extern PGDLLIMPORT int NamedLWLockTrancheRequests;
 
-/* Names for fixed lwlocks */
-#include "storage/lwlocknames.h"
-
 /*
  * It's a bit odd to declare NUM_BUFFER_PARTITIONS and NUM_LOCK_PARTITIONS
  * here, but we need them to figure out offsets within MainLWLockArray, and