Fully const-ify PQconnectdbParams, PQconnectStartParams, and PQpingParams.

The keywords and values arguments of these functions are more properly
declared "const char * const *" than just "const char **".

Lionel Elie Mamane, reviewed by Craig Ringer

doc/src/sgml/libpq.sgml

@@ -98,7 +98,9 @@
        Makes a new connection to the database server.
 
 <synopsis>
-PGconn *PQconnectdbParams(const char **keywords, const char **values, int expand_dbname);
+PGconn *PQconnectdbParams(const char * const *keywords,
+                          const char * const *values,
+                          int expand_dbname);
 </synopsis>
       </para>
 
@@ -730,8 +732,8 @@ PGconn *PQsetdb(char *pghost,
        Make a connection to the database server in a nonblocking manner.
 
 <synopsis>
-PGconn *PQconnectStartParams(const char **keywords,
-                             const char **values,
+PGconn *PQconnectStartParams(const char * const *keywords,
+                             const char * const *values,
                              int expand_dbname);
 
 PGconn *PQconnectStart(const char *conninfo);
@@ -1112,7 +1114,9 @@ PostgresPollingStatusType PQresetPoll(PGconn *conn);
        values to obtain the server status.
 
 <synopsis>
-PGPing PQpingParams(const char **keywords, const char **values, int expand_dbname);
+PGPing PQpingParams(const char * const *keywords,
+                    const char * const *values,
+                    int expand_dbname);
 </synopsis>
 
        The function returns one of the following values:

src/interfaces/libpq/fe-connect.c

@@ -291,8 +291,8 @@ static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
 static PQconninfoOption *conninfo_parse(const char *conninfo,
 			   PQExpBuffer errorMessage, bool use_defaults);
-static PQconninfoOption *conninfo_array_parse(const char **keywords,
-					 const char **values, PQExpBuffer errorMessage,
+static PQconninfoOption *conninfo_array_parse(const char *const * keywords,
+					 const char *const * values, PQExpBuffer errorMessage,
 					 bool use_defaults, int expand_dbname);
 static char *conninfo_getval(PQconninfoOption *connOptions,
 				const char *keyword);
@@ -362,8 +362,8 @@ pgthreadlock_t pg_g_threadlock = default_threadlock;
  * call succeeded.
  */
 PGconn *
-PQconnectdbParams(const char **keywords,
-				  const char **values,
+PQconnectdbParams(const char *const * keywords,
+				  const char *const * values,
 				  int expand_dbname)
 {
 	PGconn	   *conn = PQconnectStartParams(keywords, values, expand_dbname);
@@ -381,8 +381,8 @@ PQconnectdbParams(const char **keywords,
  * check server status, accepting parameters identical to PQconnectdbParams
  */
 PGPing
-PQpingParams(const char **keywords,
-			 const char **values,
+PQpingParams(const char *const * keywords,
+			 const char *const * values,
 			 int expand_dbname)
 {
 	PGconn	   *conn = PQconnectStartParams(keywords, values, expand_dbname);
@@ -464,8 +464,8 @@ PQping(const char *conninfo)
  * See PQconnectPoll for more info.
  */
 PGconn *
-PQconnectStartParams(const char **keywords,
-					 const char **values,
+PQconnectStartParams(const char *const * keywords,
+					 const char *const * values,
 					 int expand_dbname)
 {
 	PGconn	   *conn;
@@ -4249,7 +4249,7 @@ conninfo_parse(const char *conninfo, PQExpBuffer errorMessage,
  * keywords will take precedence, however.
  */
 static PQconninfoOption *
-conninfo_array_parse(const char **keywords, const char **values,
+conninfo_array_parse(const char *const * keywords, const char *const * values,
 					 PQExpBuffer errorMessage, bool use_defaults,
 					 int expand_dbname)
 {

src/interfaces/libpq/libpq-fe.h

@@ -235,14 +235,14 @@ typedef struct pgresAttDesc
 /* make a new client connection to the backend */
 /* Asynchronous (non-blocking) */
 extern PGconn *PQconnectStart(const char *conninfo);
-extern PGconn *PQconnectStartParams(const char **keywords,
-					 const char **values, int expand_dbname);
+extern PGconn *PQconnectStartParams(const char *const * keywords,
+					 const char *const * values, int expand_dbname);
 extern PostgresPollingStatusType PQconnectPoll(PGconn *conn);
 
 /* Synchronous (blocking) */
 extern PGconn *PQconnectdb(const char *conninfo);
-extern PGconn *PQconnectdbParams(const char **keywords,
-				  const char **values, int expand_dbname);
+extern PGconn *PQconnectdbParams(const char *const * keywords,
+				  const char *const * values, int expand_dbname);
 extern PGconn *PQsetdbLogin(const char *pghost, const char *pgport,
 			 const char *pgoptions, const char *pgtty,
 			 const char *dbName,
@@ -413,8 +413,8 @@ extern int	PQsetnonblocking(PGconn *conn, int arg);
 extern int	PQisnonblocking(const PGconn *conn);
 extern int	PQisthreadsafe(void);
 extern PGPing PQping(const char *conninfo);
-extern PGPing PQpingParams(const char **keywords,
-			 const char **values, int expand_dbname);
+extern PGPing PQpingParams(const char *const * keywords,
+			 const char *const * values, int expand_dbname);
 
 /* Force the write buffer to be written (or at least try) */
 extern int	PQflush(PGconn *conn);