Hi, Alan,
On Jan 21, 2010, at 22:39 , Alan W. Irwin wrote:
>> I certainly find the // comments convenient, but I recently ran
>> into a small annoyance on a project with a manually maintained
>> Makefile. I found that I needed to use the gcc compiler option...
>>
>> -std=gnu99
>>
>> ...in order to be able to use // comments and some other "basics"
>> like usleep and getopt.
>
> I just did a test of a // comment with gcc (without any special
> options),
> and it compiled fine. Could you try to confirm that for your version
> of gcc as well?
Yes, it recognizes // comments fine with no -std option, but then it
gives a warning about round(). Using -std=c99 (as indicated by "man
3 round") then gives a warning about usleep(). Using -std=gnu99 gets
it all to work. FWIW, this is with gcc 4.1.2 on CentOS 5.3.
$ gcc --version
gcc (GCC) 4.1.2 20080704 (Red Hat 4.1.2-44)
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There
is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.
$ cat foo.c
#include <unistd.h>
#include <math.h>
#ifndef NO_COMMENT
// Test usleep and round functions
#endif
double foo(double x)
{
usleep(1);
return round(x);
}
$ gcc -c -o /dev/null foo.c
foo.c: In function 'foo':
foo.c:8: warning: incompatible implicit declaration of built-in
function 'round'
$ gcc -std=c89 -c -o /dev/null foo.c
foo.c:5: error: expected identifier or '(' before '/' token
# ifndef out the // comment
$ gcc -std=c89 -DNO_COMMENTS -c -o /dev/null foo.c
(no complaints, but no // comments either)
$ gcc -std=c99 -c -o /dev/null foo.c
foo.c: In function 'foo':
foo.c:7: warning: implicit declaration of function 'usleep'
$ gcc -std=gnu99 -c -o /dev/null foo.c
(no complaints and with // comments!)
I should note that gcc 4.3.4 (on my Mac, installed via macports)
compiles the above foo.c without any -std options (and with the //
comments).
Like I said earlier, I think cmake should be able to handle any
compiler specific issues, so I don't think my whining about this
should dissuade you from changing to // comments.
Dave
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