Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 17841)
+++ wp-includes/formatting.php	(working copy)
@@ -1301,9 +1301,17 @@
  */
 function _make_url_clickable_cb($matches) {
 	$url = $matches[2];
-	$suffix = '';
 
-	/** Include parentheses in the URL only if paired **/
+	if ( ')' == $matches[3] && strpos( $url, '(' ) ) {
+		// If the trailing character is a closing parethesis, and the URL has an opening parenthesis in it, add the closing parenthesis to the URL.
+		// Then we can let the parenthesis balancer do its thing below.
+		$url .= $matches[3];
+		$suffix = '';
+	} else {
+		$suffix = $matches[3];
+	}
+
+	// Include parentheses in the URL only if paired
 	while ( substr_count( $url, '(' ) < substr_count( $url, ')' ) ) {
 		$suffix = strrchr( $url, ')' ) . $suffix;
 		$url = substr( $url, 0, strrpos( $url, ')' ) );
@@ -1372,23 +1380,105 @@
  * @param string $ret Content to convert URIs.
  * @return string Content with converted URIs.
  */
-function make_clickable($ret) {
-	$ret = ' ' . $ret;
-	// in testing, using arrays here was found to be faster
-	$save = @ini_set('pcre.recursion_limit', 10000);
-	$retval = preg_replace_callback('#(?<!=[\'"])(?<=[*\')+.,;:!&$\s>])(\()?([\w]+?://(?:[\w\\x80-\\xff\#%~/?@\[\]-]{1,2000}|[\'*(+.,;:!=&$](?![\b\)]|(\))?([\s]|$))|(?(1)\)(?![\s<.,;:]|$)|\)))+)#is', '_make_url_clickable_cb', $ret);
-	if (null !== $retval )
-		$ret = $retval;
-	@ini_set('pcre.recursion_limit', $save);
+function make_clickable( $ret ) {
+	// Long strings might contain expensive edge cases ...
+	if ( 10000 < strlen( $ret ) ) {
+		$r = '';
+		// ... break it up
+		foreach ( _split_str_by_whitespace( $ret, 2100 ) as $chunk ) { // 2100: Extra room for scheme and leading and trailing paretheses
+			if ( 2101 < strlen( $chunk ) ) {
+				$r .= $chunk; // Too big, no whitespace: bail.
+			} else {
+				$r .= make_clickable( $chunk );
+			}
+		}
+		return $r;
+	}
+
+	$ret = " $ret "; // Pad with whitespace to simplify the regexes
+
+	$url_clickable = '~
+		([\\s\\(<])                                            # 1: Leading whitespace, opening parethesis (for parethesis balancing post processing), or opening angle bracket
+		(                                                      # 2: URL
+			[\\w]{1,20}+://                                # Scheme and hier-part prefix
+			(?=\S{1,2000}\s)                               # Limit to URLs less than about 2000 characters long
+			[\\w\\x80-\\xff#%\\~/@\\[\\]*(+=&$-]*+         # Non-punctuation URL character
+			(?:                                            # Unroll the Loop: Only allow puctuation URL character if followed by a non-punctuation URL character
+				[\'.,;:!?)]                            # Punctuation URL character
+				[\\w\\x80-\\xff#%\\~/@\\[\\]*(+=&$-]++ # Non-punctuation URL character
+			)*
+		)
+		(\)?)                                                  # 3: Trailing closing parenthesis (for parethesis balancing post processing)
+	~xS'; // The regex is a non-anchored pattern and does not have a single fixed starting character.
+	      // Tell PCRE to spend more time optimizing since, when used on a page load, it will probably be used several times.
+
+	$ret = preg_replace_callback( $url_clickable, '_make_url_clickable_cb', $ret );
+
 	$ret = preg_replace_callback('#([\s>])((www|ftp)\.[\w\\x80-\\xff\#$%&~/.\-;:=,?@\[\]+]+)#is', '_make_web_ftp_clickable_cb', $ret);
 	$ret = preg_replace_callback('#([\s>])([.0-9a-z_+-]+)@(([0-9a-z-]+\.)+[0-9a-z]{2,})#i', '_make_email_clickable_cb', $ret);
-	// this one is not in an array because we need it to run last, for cleanup of accidental links within links
+
+	// Cleanup of accidental links within links
 	$ret = preg_replace("#(<a( [^>]+?>|>))<a [^>]+?>([^>]+?)</a></a>#i", "$1$3</a>", $ret);
-	$ret = trim($ret);
-	return $ret;
+	return substr( $ret, 1, -1 ); // Remove our whitespace padding.
 }
 
 /**
+ * Breaks a string into chunks by splitting at whitespace characters.
+ * The length of each returned chunk is as close to the specified length goal as possible,
+ * with the caveat that each chunk includes its trailing delimiter.
+ * Chunks longer than the goal are guaranteed to not have any inner whitespace.
+ *
+ * Joining the returned chunks with empty delimiters reconstructs the input string losslessly.
+ *
+ * Input string must have no null characters (or eventual transformations on output chunks must not care about null characters)
+ *
+ * <code>
+ * _split_str_by_whitespace( "1234 67890 1234 67890a cd 1234   890 123456789 1234567890a    45678   1 3 5 7 90 ", 10 ) ==
+ * array (
+ *   0 => '1234 67890 ',  // 11 characters: Perfect split
+ *   1 => '1234 ',        //  5 characters: '1234 67890a' was too long
+ *   2 => '67890a cd ',   // 10 characters: '67890a cd 1234' was too long
+ *   3 => '1234   890 ',  // 11 characters: Perfect split
+ *   4 => '123456789 ',   // 10 characters: '123456789 1234567890a' was too long
+ *   5 => '1234567890a ', // 12 characters: Too long, but no inner whitespace on which to split
+ *   6 => '   45678   ',  // 11 characters: Perfect split
+ *   7 => '1 3 5 7 9',    //  9 characters: End of $string
+ * );
+ * </code>
+ *
+ * @param string $string The string to split
+ * @param    int $goal   The desired chunk length.
+ *
+ * @return array Numeric array of chunks.
+ */
+function _split_str_by_whitespace( $string, $goal ) {
+	$chunks = array();
+
+	$string_nullspace = strtr( $string, "\r\n\t\v\f ", "\000\000\000\000\000\000" );
+
+	while ( $goal < strlen( $string_nullspace ) ) {
+		$pos = strrpos( substr( $string_nullspace, 0, $goal + 1 ), "\000" );
+
+		if ( false === $pos ) {
+			$pos = strpos( $string_nullspace, "\000", $goal + 1 );
+			if ( false === $pos ) {
+				break;
+			}
+		}
+
+		$chunks[] = substr( $string, 0, $pos + 1 );
+		$string = substr( $string, $pos + 1 );
+		$string_nullspace = substr( $string_nullspace, $pos + 1 );
+	}
+
+	if ( $string ) {
+		$chunks[] = $string;
+	}
+
+	return $chunks;
+}
+
+/**
  * Adds rel nofollow string to all HTML A elements in content.
  *
  * @since 1.5.0