Make various variables const (read-only).

These changes should generally improve correctness/maintainability.
A nice side benefit is that several kilobytes move from initialized
data to text segment, allowing them to be shared across processes and
probably reducing copy-on-write overhead while forking a new backend.
Unfortunately this doesn't seem to help libpq in the same way (at least
not when it's compiled with -fpic on x86_64), but we can hope the linker
at least collects all nominally-const data together even if it's not
actually part of the text segment.

Also, make pg_encname_tbl[] static in encnames.c, since there seems
no very good reason for any other code to use it; per a suggestion
from Wim Lewis, who independently submitted a patch that was mostly
a subset of this one.

Oskari Saarenmaa, with some editorialization by me

3 files changed, 6 insertions, 6 deletions

diff --git a/src/backend/regex/regc_lex.c b/src/backend/regex/regc_lex.c
index 3360cfb0e9f..c4095e98cbd 100644
--- a/src/backend/regex/regc_lex.c
+++ b/src/backend/regex/regc_lex.c
@@ -716,10 +716,10 @@ static int						/* not actually used, but convenient for RETV */
 lexescape(struct vars * v)
 {
 	chr			c;
-	static chr	alert[] = {
+	static const chr alert[] = {
 		CHR('a'), CHR('l'), CHR('e'), CHR('r'), CHR('t')
 	};
-	static chr	esc[] = {
+	static const chr esc[] = {
 		CHR('E'), CHR('S'), CHR('C')
 	};
 	const chr  *save;
diff --git a/src/backend/regex/regcomp.c b/src/backend/regex/regcomp.c
index b5988a2fbc1..ca1ccc52023 100644
--- a/src/backend/regex/regcomp.c
+++ b/src/backend/regex/regcomp.c
@@ -274,7 +274,7 @@ struct vars
 
 
 /* static function list */
-static struct fns functions = {
+static const struct fns functions = {
 	rfree,						/* regfree insides */
 };
 
diff --git a/src/backend/regex/regerror.c b/src/backend/regex/regerror.c
index f6a3f2667f8..4b2573e6255 100644
--- a/src/backend/regex/regerror.c
+++ b/src/backend/regex/regerror.c
@@ -34,10 +34,10 @@
 #include "regex/regguts.h"
 
 /* unknown-error explanation */
-static char unk[] = "*** unknown regex error code 0x%x ***";
+static const char unk[] = "*** unknown regex error code 0x%x ***";
 
 /* struct to map among codes, code names, and explanations */
-static struct rerr
+static const struct rerr
 {
 	int			code;
 	const char *name;
@@ -62,7 +62,7 @@ pg_regerror(int errcode,		/* error code, or REG_ATOI or REG_ITOA */
 			char *errbuf,		/* result buffer (unless errbuf_size==0) */
 			size_t errbuf_size) /* available space in errbuf, can be 0 */
 {
-	struct rerr *r;
+	const struct rerr *r;
 	const char *msg;
 	char		convbuf[sizeof(unk) + 50];		/* 50 = plenty for int */
 	size_t		len;