Fix PQport to never return NULL unless the connection is NULL.

This is the documented behavior, and it worked that way before
v10.  However, addition of the connhost[] array created cases
where conn->connhost[conn->whichhost].port is NULL.  The rest
of libpq is careful to substitute DEF_PGPORT[_STR] for a null
or empty port string, but we failed to do so here, leading to
possibly returning NULL.  As of v18 that causes psql's \conninfo
command to segfault.  Older psql versions avoid that, but it's
pretty likely that other clients have trouble with this,
so we'd better back-patch the fix.

In stable branches, just revert to our historical behavior of
returning an empty string when there was no user-given port
specification.  However, it seems substantially more useful and
indeed more correct to hand back DEF_PGPORT_STR in such cases,
so let's make v18 and master do that.

Author: Daniele Varrazzo <daniele.varrazzo@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CA+mi_8YTS8WPZPO0PAb2aaGLwHuQ0DEQRF0ZMnvWss4y9FwDYQ@mail.gmail.com
Backpatch-through: 13

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 2a2b10d5a29baa770fdd60b5b2db65e35ba96d69..afa85d9fca9611a393d279e4f7c637c5639bc6ee 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -7574,10 +7574,12 @@ PQport(const PGconn *conn)
    if (!conn)
        return NULL;
 
-   if (conn->connhost != NULL)
+   if (conn->connhost != NULL &&
+       conn->connhost[conn->whichhost].port != NULL &&
+       conn->connhost[conn->whichhost].port[0] != '\0')
        return conn->connhost[conn->whichhost].port;
 
-   return "";
+   return DEF_PGPORT_STR;
 }
 
 /*

diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 70c28f2ffca0b9bc9e3c651b7c671d81761980d6..a701c25038a7566b4eeebe26beed129bed572f6b 100644 (file)
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -357,7 +357,8 @@ typedef struct pg_conn_host
    pg_conn_host_type type;     /* type of host address */
    char       *host;           /* host name or socket path */
    char       *hostaddr;       /* host numeric IP address */
-   char       *port;           /* port number (always provided) */
+   char       *port;           /* port number (if NULL or empty, use
+                                * DEF_PGPORT[_STR]) */
    char       *password;       /* password for this host, read from the
                                 * password file; NULL if not sought or not
                                 * found in password file. */