What you are trying to do is somewhat fraught with peril anyway.
For example, even if the space weren't inserted when your macro
gets expanded... the resulting line of code:
printf( "%s", /usr/X11R6/lib );
isn't going to compile anyway.
But for what it's worth... I tried that same code on a linux
machine with egcs egcs-2.91.66 and I get the same results.
So you might want to bring this same question up on a gcc-specific
list somewhere since it seems to be present in multiple versions
of gcc's preprocessor and across platforms. It's not specific
to cygwin in other words.
Out of curiosity... I tried it with Visual C++ 6.0 and it does
exhibit the right behavior. So this may be a legitimate gcc
bug that the gcc maintainers need to know about nonetheless.
#line 1 "tmp.c"
int main( int argc, char *argv[] )
{
printf( "%s", /usr/X11R6/lib );
return 0;
}
By the way, you can change your code as follows to work around
the bug and produce a working program with gcc as well. The reason
this works is that ANSI-C compilers turn consecutive
whitespace-separated string literals into a single string
literal:
.../tmp$ cat tmp.c
#define Glue(a,b) a ##b
#define TestDef "/usr/X11R6"
int main( int argc, char *argv[] )
{
printf( "%s", Glue(TestDef,"/lib") );
return 0;
}
.../tmp$ gcc -E tmp.c
# 1 "tmp.c"
int main( int argc, char *argv[] )
{
printf( "%s\n", "/usr/X11R6" "/lib" );
return 0;
}
.../tmp$ gcc tmp.c
.../tmp$ ./a.out
/usr/X11R6/lib
Troy
-----Original Message-----
From: Anyos Bela [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 27, 2001 7:48 AM
To: [EMAIL PROTECTED]
Subject: 1.3.2: gcc bug (NT 4.0)
Hi Guys,
I think I found a problem in connection with
gcc 'token-pasting' operator (##)
$ gcc -v
Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/2.95.3-5/specs
gcc version 2.95.3-5 (cygwin special)
I use cygwin v1.3.2 under NT 4.0 Service Pack 6.
Here's a little example to show its failure:
( obviously it has no meaning, I used it just for demonstrating the
problem )
--------------------
#define Glue(a,b) a##b
#define TestDef /usr/X11R6
int main( int argc, char *argv[] )
{
printf( "%s", Glue( TestDef,/lib ) );
return 0;
}
---------------------
Feeding this to gcc it produces the following on my computer:
---------------------
$ gcc -E test.c
# 1 "test.c"
int main( int argc, char *argv[] )
{
printf( "%s", /usr/X11R6 /lib );
return 0;
}
---------------------
Please notice the gap between '/usr/X11R6' and '/lib'.
It only happens if the first paramter of the 'Glue' macro is
another macro. If I use a literal it works fine!
I also tested it on Linux and it worked fine there.
Thanks for your help and best regards,
Bela
ps.: Can you please cc answers to me, because I'm not on the list, yet !
Thanks !
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