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

1 files changed, 3 insertions, 3 deletions

diff --git a/src/backend/utils/mb/mbutils.c b/src/backend/utils/mb/mbutils.c
index 6d1cd8e8759..08440e9fe9d 100644
--- a/src/backend/utils/mb/mbutils.c
+++ b/src/backend/utils/mb/mbutils.c
@@ -55,9 +55,9 @@ static FmgrInfo *ToClientConvProc = NULL;
 /*
  * These variables track the currently-selected encodings.
  */
-static pg_enc2name *ClientEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
-static pg_enc2name *DatabaseEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
-static pg_enc2name *MessageEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *ClientEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *DatabaseEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
+static const pg_enc2name *MessageEncoding = &pg_enc2name_tbl[PG_SQL_ASCII];
 
 /*
  * During backend startup we can't set client encoding because we (a)