libpq: change PQconndefaults() to ignore invalid service files

Previously missing or invalid service files returned NULL.  Also fix
pg_upgrade to report "out of memory" for a null return from
PQconndefaults().

Patch by Steve Singer, rewritten by me

contrib/pg_upgrade/server.c

@@ -325,6 +325,9 @@ check_pghost_envvar(void)
 
 	start = PQconndefaults();
 
+	if (!start)
+		pg_fatal("out of memory\n");
+		
 	for (option = start; option->keyword != NULL; option++)
 	{
 		if (option->envvar && (strcmp(option->envvar, "PGHOST") == 0 ||

doc/src/sgml/libpq.sgml

@@ -483,7 +483,8 @@ typedef struct
        with an entry having a null <structfield>keyword</> pointer.  The
        null pointer is returned if memory could not be allocated. Note that
        the current default values (<structfield>val</structfield> fields)
-       will depend on environment variables and other context.  Callers
+       will depend on environment variables and other context.  A
+       missing or invalid service file will be silently ignored.  Callers
        must treat the connection options data as read-only.
       </para>
 

src/interfaces/libpq/fe-auth.c

@@ -982,7 +982,7 @@ pg_fe_sendauth(AuthRequest areq, PGconn *conn)
  * if there is an error, return NULL with an error message in errorMessage
  */
 char *
-pg_fe_getauthname(PQExpBuffer errorMessage)
+pg_fe_getauthname(void)
 {
 	const char *name = NULL;
 	char	   *authn;

src/interfaces/libpq/fe-auth.h

@@ -19,6 +19,6 @@
 
 
 extern int	pg_fe_sendauth(AuthRequest areq, PGconn *conn);
-extern char *pg_fe_getauthname(PQExpBuffer errorMessage);
+extern char *pg_fe_getauthname(void);
 
 #endif   /* FE_AUTH_H */

src/interfaces/libpq/fe-connect.c

@@ -875,7 +875,8 @@ PQconndefaults(void)
 	connOptions = conninfo_init(&errorBuf);
 	if (connOptions != NULL)
 	{
-		if (!conninfo_add_defaults(connOptions, &errorBuf))
+		/* pass NULL errorBuf to ignore errors */
+		if (!conninfo_add_defaults(connOptions, NULL))
 		{
 			PQconninfoFree(connOptions);
 			connOptions = NULL;
@@ -4412,9 +4413,10 @@ conninfo_array_parse(const char *const * keywords, const char *const * values,
  *
  * Defaults are obtained from a service file, environment variables, etc.
  *
- * Returns TRUE if successful, otherwise FALSE; errorMessage is filled in
- * upon failure.  Note that failure to locate a default value is not an
- * error condition here --- we just leave the option's value as NULL.
+ * Returns TRUE if successful, otherwise FALSE; errorMessage, if supplied,
+ * is filled in upon failure.  Note that failure to locate a default value
+ * is not an error condition here --- we just leave the option's value as
+ * NULL.
  */
 static bool
 conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
@@ -4424,9 +4426,10 @@ conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
 
 	/*
 	 * If there's a service spec, use it to obtain any not-explicitly-given
-	 * parameters.
+	 * parameters.  Ignore error if no error message buffer is passed
+	 * because there is no way to pass back the failure message.
 	 */
-	if (parseServiceInfo(options, errorMessage) != 0)
+	if (parseServiceInfo(options, errorMessage) != 0 && errorMessage)
 		return false;
 
 	/*
@@ -4448,6 +4451,7 @@ conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
 				option->val = strdup(tmp);
 				if (!option->val)
 				{
+					if (errorMessage)
 						printfPQExpBuffer(errorMessage,
 										  libpq_gettext("out of memory\n"));
 					return false;
@@ -4465,6 +4469,7 @@ conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
 			option->val = strdup(option->compiled);
 			if (!option->val)
 			{
+				if (errorMessage)
 					printfPQExpBuffer(errorMessage,
 									  libpq_gettext("out of memory\n"));
 				return false;
@@ -4477,7 +4482,7 @@ conninfo_add_defaults(PQconninfoOption *options, PQExpBuffer errorMessage)
 		 */
 		if (strcmp(option->keyword, "user") == 0)
 		{
-			option->val = pg_fe_getauthname(errorMessage);
+			option->val = pg_fe_getauthname();
 			continue;
 		}
 	}