[ticket/10057] Report postgres db connection errors.

Addresses two issues:

1. When pgsql extension is missing, @pg_connect would silently
abort execution. Check for pg_connect existence before calling it,
same with pg_pconnect.

2. When connection fails, the error reported by php is discarded.
User is shown the failure message without the reason for failure,
making debugging difficult. Collect the error (if any) via a
temporarily installed error handler, and display it if connection
failed.

PHPBB3-10057

phpBB/includes/db/postgres.php

@@ -81,13 +81,25 @@ class dbal_postgres extends dbal
 
 		if ($this->persistency)
 		{
+			if (!function_exists('pg_pconnect'))
+			{
+				return $this->sql_error('pg_pconnect does not exist');
+			}
+			phpbb_start_error_collection();
 			$this->db_connect_id = (!$new_link) ? @pg_pconnect($connect_string) : @pg_pconnect($connect_string, PGSQL_CONNECT_FORCE_NEW);
 		}
 		else
 		{
+			if (!function_exists('pg_pconnect'))
+			{
+				return $this->sql_error('pg_connect does not exist');
+			}
+			phpbb_start_error_collection();
 			$this->db_connect_id = (!$new_link) ? @pg_connect($connect_string) : @pg_connect($connect_string, PGSQL_CONNECT_FORCE_NEW);
 		}
 
+		$errors = phpbb_stop_error_collection();
+
 		if ($this->db_connect_id)
 		{
 			if (version_compare($this->sql_server_info(true), '8.2', '>='))
@@ -102,7 +114,8 @@ class dbal_postgres extends dbal
 			return $this->db_connect_id;
 		}
 
-		return $this->sql_error('');
+		$errors = phpbb_format_collected_errors($errors);
+		return $this->sql_error($errors);
 	}
 
 	/**

phpBB/includes/functions.php

@@ -3928,6 +3928,50 @@ function msg_handler($errno, $msg_text, $errfile, $errline)
 	return false;
 }
 
+function phpbb_error_collection_handler($errno, $msg_text, $errfile, $errline)
+{
+	global $phpbb_collected_errors;
+	$phpbb_collected_errors[-1][] = array($errno, $msg_text, $errfile, $errline);
+}
+
+function phpbb_start_error_collection()
+{
+	global $phpbb_collected_errors;
+	if (!isset($phpbb_collected_errors))
+	{
+		$phpbb_collected_errors = array();
+	}
+	$phpbb_collected_errors[] = array();
+	set_error_handler('phpbb_error_collection_handler');
+}
+
+function phpbb_stop_error_collection()
+{
+	global $phpbb_collected_errors;
+	restore_error_handler();
+	$errors = array_pop($phpbb_collected_errors);
+	return $errors;
+}
+
+function phpbb_format_collected_errors($errors)
+{
+	$text = '';
+	foreach ($errors as $error)
+	{
+		if (!empty($text))
+		{
+			$text .= "<br />\n";
+		}
+		list($errno, $msg_text, $errfile, $errline) = $error;
+		$text .= "Errno $errno: $msg_text";
+		if (defined('DEBUG'))
+		{
+			$text .= " at $errfile line $errline";
+		}
+	}
+	return $text;
+}
+
 /**
 * Queries the session table to get information about online guests
 * @param int $item_id Limits the search to the item with this id