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Groups > comp.lang.c > #105138
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: writing a c program to substitute text |
| Date | 2017-02-28 19:38 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <o94fup$9g7$1@dont-email.me> (permalink) |
| References | <ehfv4oFu00sU1@mid.individual.net> <6b1df453-b6df-3cf8-eb6e-255c37ef241a@verizon.net> <ehl892F1h4hU1@mid.individual.net> <o93ucu$3nv$1@dont-email.me> <lno9xme0md.fsf@kst-u.example.com> |
On 28/02/17 17:33, Keith Thompson wrote: > David Brown <david.brown@hesbynett.no> writes: >> On 28/02/17 13:20, fred flintstone wrote: > [...] >>> gcc -Wall -Wextra -o sub1 sub1.c >text1.txt >> >> You should add "-O1" to that list - it lets gcc do better analysis for >> more warnings. > > Why do you recommend -O1 rather than -O3? -O1 is enough to enable the analysis passes that give better warnings - as far as I know, you don't get more static analysis with greater optimisation levels. It can vary whether -O3 is actually any faster than -O2 - so usually -O2 is picked for "fast code". If you need more than that, you probably want to consider other flags like "-march=native" or "-ffast-math", and perhaps using extra compiler features (attributes, etc.) if portability is not an issue. In general, I'd say "-O1" if you want to do debugging or view the generated assembly (since the structure of your source code is more visible in the generated output), and "-O2" if you want faster code. > > If you want to write standard C, I'd also recommend > -std=c11 -pedantic-errors Agreed, if you want to check for standards compliance (at least, as good a check as you can conveniently get with little effort). I don't usually think about -pedantic flags, simply because for my own work I use -std=gnu11 and make use of a number of gcc extensions - portability across compilers is not an issue for most of what I do. But certainly sticking to the standards is a good idea for someone learning C. > > If you use -pedantic rather than -pedantic-errors, some errors will be > diagnosed with non-fatal warnings; that's ok if you treat warnings > *very* seriously. > I like to use -Werror - I /do/ treat warnings very seriously. But that's me - it is not necessarily a good idea for everyone.
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writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-26 04:14 -0800
Re: writing a c program to substitute text fir <profesor.fir@gmail.com> - 2017-02-26 04:55 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-26 14:28 +0100
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-27 03:58 -0800
Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-27 13:11 +0000
Re: writing a c program to substitute text BartC <bc@freeuk.com> - 2017-02-27 13:33 +0000
Re: writing a c program to substitute text scott@slp53.sl.home (Scott Lurndal) - 2017-02-27 17:12 +0000
Re: writing a c program to substitute text BartC <bc@freeuk.com> - 2017-02-27 17:59 +0000
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 19:05 +0100
Re: writing a c program to substitute text scott@slp53.sl.home (Scott Lurndal) - 2017-02-27 18:37 +0000
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-27 11:40 -0800
Re: writing a c program to substitute text Manfred <noname@invalid.add> - 2017-02-27 16:03 +0100
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-01 05:33 -0800
Re: writing a c program to substitute text "D. Aaron Sawyer" <aaron@110.net> - 2017-03-01 10:32 -0400
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-01 06:59 -0800
Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-01 15:24 +0000
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-02 01:47 -0800
Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-02 11:05 +0000
Re: writing a c program to substitute text jt@toerring.de (Jens Thoms Toerring) - 2017-02-27 13:33 +0000
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-27 09:10 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 19:07 +0100
Re: writing a c program to substitute text jt@toerring.de (Jens Thoms Toerring) - 2017-02-27 18:23 +0000
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 14:46 +0100
Re: writing a c program to substitute text James Kuyper <jameskuyper@verizon.net> - 2017-02-27 09:27 -0500
Re: writing a c program to substitute text GOTHIER Nathan <nathan.gothier@gmail.com> - 2017-02-27 15:28 +0100
Re: writing a c program to substitute text James Kuyper <jameskuyper@verizon.net> - 2017-02-27 09:38 -0500
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 15:44 +0100
Re: writing a c program to substitute text James Kuyper <jameskuyper@verizon.net> - 2017-02-27 10:36 -0500
Re: writing a c program to substitute text Anglican <h.toms@qmul.ac.uk> - 2017-02-27 15:50 +0000
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 17:13 +0100
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-27 16:30 -0800
Re: writing a c program to substitute text fir <profesor.fir@gmail.com> - 2017-02-27 07:08 -0800
Re: writing a c program to substitute text fir <profesor.fir@gmail.com> - 2017-02-27 07:20 -0800
Re: writing a c program to substitute text fir <profesor.fir@gmail.com> - 2017-02-27 07:24 -0800
Re: writing a c program to substitute text Manfred <noname@invalid.add> - 2017-02-27 16:00 +0100
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-27 09:22 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 19:11 +0100
Re: writing a c program to substitute text John Bode <jfbode1029@gmail.com> - 2017-02-28 15:41 -0800
solved Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-02 01:25 -0800
Re: solved Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-03-02 11:28 +0100
Re: solved Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-02 10:54 +0000
Re: solved Re: writing a c program to substitute text Manfred <noname@invalid.add> - 2017-03-02 15:28 +0100
Re: solved Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-02 14:51 +0000
Re: solved Re: writing a c program to substitute text John Bode <jfbode1029@gmail.com> - 2017-03-02 14:18 -0800
Re: solved Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-03-02 23:55 +0000
Re: solved Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-14 18:32 -0700
Re: writing a c program to substitute text Tim Rentsch <txr@alumni.caltech.edu> - 2017-04-17 07:04 -0700
Re: writing a c program to substitute text jladasky@itu.edu - 2017-02-27 13:48 -0800
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-27 14:16 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 08:47 +0100
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-28 01:59 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 11:39 +0100
Re: writing a c program to substitute text Richard Heathfield <rjh@cpax.org.uk> - 2017-02-28 12:03 +0000
Re: writing a c program to substitute text BartC <bc@freeuk.com> - 2017-02-28 13:33 +0000
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 14:43 +0100
Re: writing a c program to substitute text BartC <bc@freeuk.com> - 2017-02-28 13:59 +0000
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-03-01 04:26 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 23:29 +0100
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-27 15:10 -0800
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-26 06:42 -0800
Re: writing a c program to substitute text Richard Heathfield <rjh@cpax.org.uk> - 2017-02-26 16:54 +0000
[OT] "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2017-02-27 00:56 +0800
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-26 13:36 -0800
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-26 14:53 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 00:53 +0100
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-26 17:30 -0800
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-26 17:44 -0800
Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-27 01:46 +0000
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 09:29 +0100
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-27 02:12 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-27 13:11 +0100
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-27 04:41 -0800
Re: writing a c program to substitute text Malcolm McLean <malcolm.mclean5@btinternet.com> - 2017-02-27 05:04 -0800
Re: writing a c program to substitute text Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-02-27 13:25 +0000
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-27 09:56 -0800
Re: writing a c program to substitute text "Mr. Man-wai Chang" <toylet.toylet@gmail.com> - 2017-02-27 01:00 +0800
Re: writing a c program to substitute text "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-26 18:55 -0500
Re: writing a c program to substitute text fred flintstone <fred@server.invalid> - 2017-02-28 04:20 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 14:38 +0100
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-28 08:33 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 19:38 +0100
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-28 11:40 -0800
Re: writing a c program to substitute text David Brown <david.brown@hesbynett.no> - 2017-02-28 21:03 +0100
Re: gcc optimization levels Noob <root@127.0.0.1> - 2017-02-28 22:55 +0100
Re: writing a c program to substitute text "James R. Kuyper" <jameskuyper@verizon.net> - 2017-02-28 11:43 -0500
Re: writing a c program to substitute text Keith Thompson <kst-u@mib.org> - 2017-02-28 08:46 -0800
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