BUG #6216: Calling PQconnectdbParams from C++ with a char**

The following bug has been logged online:

Bug reference: 6216
Logged by: Lionel Elie Mamane
Email address: lionel(at)mamane(dot)lu
PostgreSQL version: 9.1.0
Operating system: Debian GNU/Linux
Description: Calling PQconnectdbParams from C++ with a char**
Details:

In C++, a "char**" value is not convertible to a "const char**" value,
because that is not safe (see
http://www.parashift.com/c++-faq-lite/const-correctness.html#faq-18.17).

This means one cannot call libpq's PQconnectdbParams and friends passing
them a "char**" value for keywords and/or values, as these arguments are
declared "const char**".

So please apply this patch, which declares them "char const* const*"
instead, which is:
- equivalent to "const char * const*"; use that one if you prefer
- still true, since libpq won't write to they keyword/values arrays
- allows to pass a "char**" to them and be recognised by a C++ compiler as
OK without a cast.

This patch is licensed under a "do whatever you want with it" license.

Thanks in advance.

--- postgresql-9.1-9.1.0.orig/src/interfaces/libpq/fe-connect.c
+++ postgresql-9.1-9.1.0/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(char const* const*keywords,
+ char const* 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
* call succeeded.
*/
PGconn *
-PQconnectdbParams(const char **keywords,
- const char **values,
+PQconnectdbParams(char const* const*keywords,
+ char const* 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(char const* const*keywords,
+ char const* 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(char const* const*keywords,
+ char const* const*values,
int expand_dbname)
{
PGconn *conn;
@@ -4249,7 +4249,7 @@ conninfo_parse(const char *conninfo, PQE
* keywords will take precedence, however.
*/
static PQconninfoOption *
-conninfo_array_parse(const char **keywords, const char **values,
+conninfo_array_parse(char const* const*keywords, char const* const*values,
PQExpBuffer errorMessage, bool use_defaults,
int expand_dbname)
{
--- postgresql-9.1-9.1.0.orig/src/interfaces/libpq/libpq-fe.h
+++ postgresql-9.1-9.1.0/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(char const* const*keywords,
+ char const* 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(char const* const*keywords,
+ char const* 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
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(char const* const*keywords,
+ char const* const*values, int expand_dbname);

/* Force the write buffer to be written (or at least try) */
extern int PQflush(PGconn *conn);