tech-toolchain archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: traditional cpp

On Mon, Dec 20, 2010 at 12:45:30PM +0000, David Laight wrote:
 > > How's it
 > > supposed to be done? Right now it's removing comments after macro
 > > expansion, but if it removes comments before macro expansion then /**/
 > > doesn't work for pasting... or else it has to be treated specially and
 > > stripped out again afterwards?
 > I think the /*...*/ is treated as a single token.

In Standard C, yes. Traditional cpp doesn't tokenize anything, it just
matches words.

 > Did the original cpp put spaces between output token?


 > Passing comments through to the output also requires that // comments
 > get converted to /*...*/ ones - otherwise continuation lines cause grief.

Yeah. Well, not exactly, because continuation lines are handled early;
a continuation line inside a // comment continues the comment. The
problem is that if you do

   #define A    a // blah
   #define B    b
   A B

the output without comments stripped would be

   a // blah b

which is at least misleading and possibly totally wrong.

However, really traditional traditional-cpp doesn't handle // comments. :-)
(Arguably it should also reject #if and only accept #ifdef/#ifndef.
But it wouldn't be useful this way.)

David A. Holland

Home | Main Index | Thread Index | Old Index