Re: [XForms] fdesign created c files, invalid conversion

[Jens Thoms Toerring]

Hi John,

On Thu, Oct 28, 2010 at 01:08:06PM -0700, John Wang wrote:
> I am using the currently latest version of xforms on a 64 bit ubuntu 10.10. 
> Whenever I created a c file with fdesign, gcc will complain about invalid 
> conversion from void* to FD_foo* at the line:
> 
> FD_foo *fdui = fl_malloc( sizeof *fdui );
> 
> to fix it, I will need to cast it properly like so:
> 
> FD_foo *fdui =  (FD_foo) fl_malloc( sizeof *fdui );

I guess you meant to use '(FD_foo*)' for the cast.

As far as I know without the cast it's correct standard C, so
I suspect that you're actually compiling with a C++ compiler
because C++ is more picky in this respect (it doesn't do the
automatic conversion from a void pointer to any other object
pointer). Is that the case?

> is there a way to avoid having to fix this manually everytime?

Unfortunately, not at the moment. I will change fdesign so
that the cast is automatically added to allow compilation
with C++ compilers (I took that out quite some time ago,
not considering that people might use C++ compilers, and
nobody complained until now;-). But that will only fix
things if you then use the new version to be uploaded.
I'm sorry for the inconvenience!

I will fix that ASAP and make a new release that outputs
files that get accepted by C++ compilers also.

Another fix would be to run a small script over the .c files
created by fdesign. Here's a Perl script that does that job
(hopefully, I just tested it with a single file):

---------------8<----------------------------------------
#!/usr/bin/perl
use warnings;
use strict;
open my $f, '<', $ARGV[ 0 ]
    or die "Can't open $ARGV[ 0 ] for reading: $!\n";
my @lines;
push @lines, $_ for <$f>;
close $f;
open $f, '>', $ARGV[ 0 ]
    or die "Can't open $ARGV[ 0 ] for writing: $!\n";
for ( @lines ) {
    s/^\s+(FD_[a-z0-9_]+) \*fdui = (fl_malloc.+)$/    $1 *fdui = ($1*) $2/i;
    print $f $_;
}
close $f;
---------------8<----------------------------------------

Pass it the name of the file you want to convert and the
casts should get added. (Please note: since it does in-place
replacement, i.e. overwrites the original file, you may want
to make a backup of the original file for the case that some-
thing goes wrong...)
                           Best regards, Jens
-- 
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   \_______________________________      http://toerring.de