From: | Merlin Moncure <mmoncure(at)gmail(dot)com> |
---|---|
To: | Lionel Elie Mamane <lionel(at)mamane(dot)lu> |
Cc: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #6216: Calling PQconnectdbParams from C++ with a char** |
Date: | 2011-09-20 23:29:01 |
Message-ID: | CAHyXU0zBa_2k+U1krDirt_rBp118oXt6pcB-SP+1wpfeZ2RZYA@mail.gmail.com |
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Lists: | pgsql-bugs |
On Tue, Sep 20, 2011 at 11:05 AM, Lionel Elie Mamane <lionel(at)mamane(dot)lu> wrote:
>
> 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);
I agree with the rationale. Note query parameter arguments are
already declared this way.
merlin
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