emacs and "linux" coding style
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From: Dimitrios Apostolou on 13 Jul 2010 10:00 Hello list, according to Documentation/CodingStyle the "linux" style of emacs is broken because it uses tabs+spaces when continuing the argument list of a function on a new line. So I reported that as a bug to bug-gnu-emacs (bug#6617). However it's not clear if this is a bug of emacs or an inconsistency of the linux kernel coding style. I can't find where exactly the usage *only* of tabs is mandated, see for example the following quote: > Statements longer than 80 columns will be broken into sensible > chunks. Descendants are always substantially shorter than the parent > and are placed substantially to the right. The same applies to > function headers with a long argument list. Long strings are as well > broken into shorter strings. The only exception to this is where > exceeding 80 columns significantly increases readability and does not > hide information. Tabs are not mentioned anywhere, besides the specific part about emacs which is so ironic that no emacs dev can read it fully. Moreover there are many parts in the kernel that are aligned using both tabs and spaces. Random example in the linux-2.6.34.1 kernel: kernel/sched.c static void update_group_shares_cpu(struct task_group *tg, int cpu, unsigned long sd_shares, unsigned long sd_rq_weight, unsigned long *usd_rq_weight) { So what do you think? Should the current emacs "linux" style be fixed, or are spaces allowed? Thanks, Dimitris -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Randy Dunlap on 13 Jul 2010 18:20 On Tue, 13 Jul 2010 17:00:21 +0300 (EEST) Dimitrios Apostolou wrote: > Hello list, > > according to Documentation/CodingStyle the "linux" style of emacs is > broken because it uses tabs+spaces when continuing the argument list of a > function on a new line. So I reported that as a bug to bug-gnu-emacs > (bug#6617). > > However it's not clear if this is a bug of emacs or an inconsistency of > the linux kernel coding style. I can't find where exactly the usage *only* > of tabs is mandated, see for example the following quote: > > > > Statements longer than 80 columns will be broken into sensible > > chunks. Descendants are always substantially shorter than the parent > > and are placed substantially to the right. The same applies to > > function headers with a long argument list. Long strings are as well > > broken into shorter strings. The only exception to this is where > > exceeding 80 columns significantly increases readability and does not > > hide information. See CodingStyle, Chapter 1, Indentation: "Outside of comments, documentation and except in Kconfig, spaces are never used for indentation, and the above example is deliberately broken." which to me means "spaces alone are never used (unless the indentation is less than 8 columns)". > Tabs are not mentioned anywhere, besides the specific part about emacs > which is so ironic that no emacs dev can read it fully. Moreover there are > many parts in the kernel that are aligned using both tabs and spaces. > Random example in the linux-2.6.34.1 kernel: kernel/sched.c > > > static void update_group_shares_cpu(struct task_group *tg, int cpu, > unsigned long sd_shares, > unsigned long sd_rq_weight, > unsigned long *usd_rq_weight) > { In the example above, some email software seems to have munged tabs into spaces, or someone used copy-and-paste, which also translated tabs into spaces. It should have been: static void update_group_shares_cpu(struct task_group *tg, int cpu, unsigned long sd_shares, unsigned long sd_rq_weight, unsigned long *usd_rq_weight) { which is a common usage model in the Linux kernel. > So what do you think? Should the current emacs "linux" style be fixed, or > are spaces allowed? <tab(s)>+<less than 8 spaces> are often used for function parameter alignment, as above. More than 7 spaces should not be used. I don't find the function parameter alignment very important, so sometimes I just use tabs and no spaces and omit the parameter alignment, but mostly what I do is match the current existing style in the code that I am working on. I'm not an emacs (O.S.) user, but I doubt that the emacs linux style needs to be fixed. --- ~Randy *** Remember to use Documentation/SubmitChecklist when testing your code *** -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Theodore Tso on 14 Jul 2010 02:20 On Jul 13, 2010, at 6:19 PM, Randy Dunlap wrote: > > See CodingStyle, Chapter 1, Indentation: > > "Outside of comments, documentation and except in Kconfig, spaces are never > used for indentation, and the above example is deliberately broken." > > which to me means "spaces alone are never used (unless the indentation is less than > 8 columns)". There is a huge amount of code --- including code which I submitted back in the 0.12 days of Linux --- which uses spaces to align continuation lines for function parameters, i.e. static int foo(struct inode inode, struct file *file, int flags, size_t len) such that "struct" and "size_t" are aligned on the same column, and also so that: unsigned int num = ((len + sizeof(struct foobaz) - 3) / (4 + sizeof(struct foobaz))); I've always read indentation as referring to indentation for the beginning of code lines, but not to making function parameters or paraenthesis line up. This is something which emacs does automatically, but vi does not. People who are anal enough to worry about this sort of thing, in general, IMHO, really should find better things to do. And if checkpatch.pl were to be "improved" to start issue warnings about code not adhering to this CodingStyle assertion, #1, you would find out how much code doesn't adhere to this, and #2, I think a lot of people, including myself, would be complaining vociferously and agitating to have that language removed from CodingStyle as being an actively harmful and incorrect recommendation. -- Ted -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Dimitrios Apostolou on 15 Jul 2010 08:00 Hi, On Wed, 14 Jul 2010, Theodore Tso wrote: > I've always read indentation as referring to indentation for the beginning of > code lines, but not to making function parameters or paraenthesis line > up. This is something which emacs does automatically, but vi does not. > > People who are anal enough to worry about this sort of thing, in general, > IMHO, really should find better things to do. And if checkpatch.pl were to > be "improved" to start issue warnings about code not adhering to this > CodingStyle assertion, #1, you would find out how much code doesn't > adhere to this, and #2, I think a lot of people, including myself, would be > complaining vociferously and agitating to have that language removed > from CodingStyle as being an actively harmful and incorrect recommendation. if two kernel developers agree that tabs-only alignment of arglists is not necessary, then my guess is that the CodingStyle document is broken and needs to be fixed. Quote from Documentation/CodingStyle: That's OK, we all do. You've probably been told by your long-time Unix user helper that "GNU emacs" automatically formats the C sources for you, and you've noticed that yes, it does do that, but the defaults it uses are less than desirable (in fact, they are worse than random typing - an infinite number of monkeys typing into GNU emacs would never make a good program). So, you can either get rid of GNU emacs, or change it to use saner values. To do the latter, you can stick the following in your .emacs file: If emacs' style is OK then why all this inflamatory talk is needed, and why is a patch proposed? The only thing needed is to use the "linux" c-style. Thanks, Dimitris P.S. CC'd the author of latest emacs-related patch in CodingStyle -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Krzysztof Halasa on 17 Jul 2010 05:30
Dimitrios Apostolou <jimis(a)gmx.net> writes: > static void update_group_shares_cpu(struct task_group *tg, int cpu, > unsigned long sd_shares, > unsigned long sd_rq_weight, > unsigned long *usd_rq_weight) > { From a technical POV the above should not have any tabs, the parameters should be aligned with spaces only. The tabs should be used for (syntactic) indentation only. This way we can display the code correctly with any tab length. -- Krzysztof Halasa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |