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| From | Keith Thompson <kst-u@mib.org> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: macro |
| Date | 2012-01-15 08:00 -0800 |
| Organization | None to speak of |
| Message-ID | <lnwr8t0xd2.fsf@nuthaus.mib.org> (permalink) |
| References | <89018f82-9f45-4e72-a0a2-8424e91752b6@g41g2000yqa.googlegroups.com> |
dspfun <dspfun@hotmail.com> writes:
> Can you see anything wrong or "bad" with the following macro?
>
> #define LOG(level, msg) \
> openlog (__FUNCTION__, LOG_CONS | LOG_PID | LOG_NDELAY, LOG_USER);
> \
> syslog (level, "%s", msg);\
> closelog ();
>
> I have problems using the macro with ternary operators. I believe it
> should have parantheses around it all, but I cannot get it right.
If you want the macro to be usable *as a statement*, you
should use the do ... while (0) trick; see question 10.4
in the comp.lang.c FAQ, http://c-faq.com/. Each occurrence
of any parameter name in the macro should be in parentheses.
See <https://github.com/Keith-S-Thompson/42> for an example of what
can happen if you don't follow this rule.
If you need to to be usable *as an expression*, you can't use
do/while -- but you can use the comma operator. In addition to
parenthesizing each parameter reference, the entire definition
should be enclosed in parentheses.
--
Keith Thompson (The_Other_Keith) kst-u@mib.org <http://www.ghoti.net/~kst>
Will write code for food.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
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macro dspfun <dspfun@hotmail.com> - 2012-01-15 05:29 -0800
Re: macro Dr Nick <3-nospam@temporary-address.org.uk> - 2012-01-15 13:44 +0000
Re: macro dspfun <dspfun@hotmail.com> - 2012-01-15 05:58 -0800
Re: macro "Joachim Schmitz" <nospam.jojo@schmitz-digital.de> - 2012-01-15 15:34 +0100
Re: macro "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-01-15 06:37 -0800
Re: macro dspfun <dspfun@hotmail.com> - 2012-01-15 07:28 -0800
Re: macro Philip Lantz <prl@canterey.us> - 2012-01-15 17:30 -0800
Re: macro Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-16 00:18 -0800
Re: macro Hans Vlems <hvlems@freenet.de> - 2012-01-16 00:52 -0800
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-16 22:08 +1300
Re: macro Nick Keighley <nick_keighley_nospam@hotmail.com> - 2012-01-16 03:04 -0800
Re: macro Markus Wichmann <nullplan@gmx.net> - 2012-01-16 12:42 +0100
Re: macro jgk@panix.com (Joe keane) - 2012-01-16 14:48 +0000
Re: macro Keith Thompson <kst-u@mib.org> - 2012-01-16 12:01 -0800
Re: macro Philip Lantz <prl@canterey.us> - 2012-01-17 01:02 -0800
Re: macro Keith Thompson <kst-u@mib.org> - 2012-01-17 13:05 -0800
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-18 13:12 +1300
Re: macro dspfun <dspfun@hotmail.com> - 2012-01-18 01:05 -0800
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-18 22:57 +1300
Re: macro "osmium" <r124c4u102@comcast.net> - 2012-01-18 06:22 -0600
Re: macro dspfun <dspfun@hotmail.com> - 2012-01-18 07:50 -0800
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-20 14:09 +1300
Re: macro blp@cs.stanford.edu (Ben Pfaff) - 2012-01-18 11:28 -0800
Re: macro Kaz Kylheku <kaz@kylheku.com> - 2012-01-18 21:09 +0000
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-20 15:08 +1300
[OT] Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-20 15:58 +1300
Re: [OT] Re: macro Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-01-20 12:22 +0000
Re: [OT] Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-21 07:58 +1300
Re: macro James Kuyper <jameskuyper@verizon.net> - 2012-01-19 22:47 -0500
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-20 17:06 +1300
Re: macro James Kuyper <jameskuyper@verizon.net> - 2012-01-20 00:12 -0500
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-20 18:28 +1300
Re: macro Keith Thompson <kst-u@mib.org> - 2012-01-20 03:21 -0800
Re: macro Shao Miller <sha0.miller@gmail.com> - 2012-01-20 10:50 -0500
Re: macro Shao Miller <sha0.miller@gmail.com> - 2012-01-20 11:46 -0500
Re: macro Keith Thompson <kst-u@mib.org> - 2012-01-18 14:24 -0800
Re: macro jgk@panix.com (Joe keane) - 2012-01-18 22:36 +0000
Re: macro Kaz Kylheku <kaz@kylheku.com> - 2012-01-18 22:50 +0000
Re: macro jgk@panix.com (Joe keane) - 2012-01-17 22:08 +0000
Re: macro Keith Thompson <kst-u@mib.org> - 2012-01-15 08:00 -0800
Re: macro NEON China BLUE <chine.bleu@yahoo.com> - 2012-01-15 08:15 -0800
Re: macro Ian Collins <ian-news@hotmail.com> - 2012-01-16 09:04 +1300
Re: macro Philip Lantz <prl@canterey.us> - 2012-01-15 17:36 -0800
Re: macro Jorgen Grahn <grahn+nntp@snipabacken.se> - 2012-01-16 12:01 +0000
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