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

From: "Lionel Elie Mamane" <lionel(at)mamane(dot)lu>
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #6216: Calling PQconnectdbParams from C++ with a char**
Date: 2011-09-20 16:05:55
Message-ID: 201109201605.p8KG5tku049175@wwwmaster.postgresql.org (view raw or flat)
Thread:
Lists: pgsql-bugs
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);

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Next:From: Chris GernonDate: 2011-09-20 17:17:47
Subject: BUG #6217: to_char() gives incorrect output for very small float values
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Subject: BUG #6215: ODBC - ovelflow with the OIDs - Large Objects

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