From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 16226 invoked by alias); 19 Feb 2007 22:20:41 -0000 Received: (qmail 16180 invoked by alias); 19 Feb 2007 22:20:28 -0000 Date: Mon, 19 Feb 2007 22:20:00 -0000 Message-ID: <20070219222028.16179.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug preprocessor/30805] [4.1/4.2/4.3 Regression] Internal compiler error when using "x##,##__VA_ARGS__" in macro In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "joseph at codesourcery dot com" Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2007-02/txt/msg02282.txt.bz2 ------- Comment #3 from joseph at codesourcery dot com 2007-02-19 22:20 ------- Subject: Re: [4.1/4.2/4.3 Regression] Internal compiler error when using "x##,##__VA_ARGS__" in macro The order of evaluation of ## operators is unspecified. If the left ## is evaluated first, it tries to concatenate "1" with ",", yielding undefined behavior (for some time GCC has diagnosed such attempts at concatenation yielding invalid preprocessing tokens). If the right ## is evaluated first, the GNU extension for concatenation of "," with empty __VA_ARGS__ is engaged; this presumably should leave a placemarker token, whose concatenation with "1" yields "1". -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30805