Messages in this thread | | | Date | Wed, 11 Apr 2007 00:37:44 +0400 | From | Alexey Dobriyan <> | Subject | Re: [PATCH] Add spaces on either side of case "..." operator. |
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On Tue, Apr 10, 2007 at 09:05:55AM -0700, Andrew Morton wrote: > On Tue, 10 Apr 2007 07:23:35 -0400 (EDT) "Robert P. J. Day" <rpjday@mindspring.com> wrote: > > Following the programming advice laid down in the gcc manual, make > > sure the case "..." operator has spaces on either side.
> > http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Case-Ranges.html#Case-Ranges: > > > > "Be careful: Write spaces around the ..., for otherwise it may be > > parsed wrong when you use it with integer values."
> > --- a/kernel/audit.c > > +++ b/kernel/audit.c > > @@ -515,8 +515,8 @@ static int audit_netlink_ok(struct sk_buff *skb, u16 msg_type) > > err = -EPERM; > > break; > > case AUDIT_USER: > > - case AUDIT_FIRST_USER_MSG...AUDIT_LAST_USER_MSG: > > - case AUDIT_FIRST_USER_MSG2...AUDIT_LAST_USER_MSG2: > > + case AUDIT_FIRST_USER_MSG ... AUDIT_LAST_USER_MSG: > > + case AUDIT_FIRST_USER_MSG2 ... AUDIT_LAST_USER_MSG2: > > hm... We have: > > #define AUDIT_FIRST_USER_MSG 1100 /* Userspace messages mostly uninteresting to kernel */ > #define AUDIT_USER_AVC 1107 /* We filter this differently */ > #define AUDIT_LAST_USER_MSG 1199 > > and CPP turns that into > > case 1100 ...1199: > case 2100 ...2999: > > and it does the same when the comments are stripped from the #defines. > > So we were saved by the trailing space which cpp added to the expanded > macro. I wonder why cpp did that, and to what extent one can rely cpp > doing that.
The only reason I can come up with is temporary files with preprocessing output. Imagine the code:
#define FOO 1 FOO.
Here we have a) replacement list of token FOO consists of one token -- 1, b) pp-token list after preprocessing consists of 4 pp-tokens: newline, 1, ., newline
BUT, write it to temporary file:
1.
Whoops, there are 3 or 4 pp-tokens? If you don't know history, there are 3, if you do, there are 4.
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