Re: GNOME CVS: libxslt kloczek

[James Henstridge <james daa com au>]

On 16/02/04 15:39, Daniel Veillard wrote:

> There isn't even a bug number associated to the commit or a 
> description of the problem actually occuring.

While I don't agree with the way this change was made, it is something 
that should be reviewed in all modules that install M4 macros for use by 
other packages.

The problem is that failing to quote the first argument to AC_DEFUN() 
can cause problems (ones that are difficult to debug if you aren't 
expecting them).  Automake 1.8 now checks for this condition because 
they want to have the option of making changes in the future that might 
trigger the bug in those macros.

The crux of the problem is what happens if a particular macro is defined 
twice (eg. if the .m4 file got included twice in aclocal.m4 by 
mistake).  Consider the following code snippet:
   AC_DEFUN(foo, bar)
   AC_DEFUN(foo, bar)
This actually defines two macros: one that translates "foo" to "bar", 
and the other that translates "bar" to "bar".  This is because the first 
argument in the second AC_DEFUN gets expanded (the errors are even more 
cryptic if the macro has a more complicated body).

In comparison, the following snippet only defines a single "foo" -> 
"bar" macro:
   AC_DEFUN([foo], [bar])
   AC_DEFUN([foo], [bar])

While you may not have received any bug reports about it (yet), it is 
definitely good practice to quote the arguments to AC_DEFUN.

James.

--
Email: james daa com au
WWW:   http://www.daa.com.au/~james/


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