------- 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
