Messages in this thread | | | From | jim.cromie@gmail ... | Date | Sat, 26 Jun 2021 21:47:11 -0600 | Subject | Re: [PATCH 2/3] checkpatch: tweak extern in C warning |
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On Sat, Jun 26, 2021 at 12:46 PM Joe Perches <joe@perches.com> wrote: > > On Fri, 2021-06-25 at 21:40 -0600, Jim Cromie wrote: > > The extern-in-C rule has one important exception: the symbol is > > defined in/by the linker script. By convention, these almost always > > contain: _start, _stop, _end. Suppress the warning on such symbols. > [] > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > > [] > > @@ -6910,7 +6910,8 @@ sub process { > > $stat =~ /^.\s*extern\s+/) > > { > > WARN("AVOID_EXTERNS", > > - "externs should be avoided in .c files\n" . $herecurr); > > + "externs should be avoided in .c files\n($stat)\n" . $herecurr) > > + unless $stat =~ /_start|_stop|_end/; > > nak. > > As far as I can tell, there's no reason these symbols > should not be in .h files. >
judging from the codebase, it has been a case-by-case decision, with 8/10 of the linker-vars extern'd into C files, not headers.
[jimc@frodo wk-test]$ perl -ne '/(\w*_(?:start|stop|end)(?:_\w+))/ and print "$1\n"' `find . -name \*.lds.h` > symbols [jimc@frodo wk-test]$ wc symbols 99 99 2112 symbols [jimc@frodo wk-test]$ grep -n -r --exclude-dir=builds/ -f symbols . | grep -E '\.c:' | grep extern | wc 79 331 6402 [jimc@frodo wk-test]$ grep -n -r --exclude-dir=builds/ -f symbols . | grep -E '\.h' | grep extern | wc 19 81 1581
8/10 cases dont expose these symbols in headers, Makes sense to me, mostly theyre internal, and often double-underscored too. 2/10 are presumably in headers for specific reasons.
> besides that: > > output is single line, $stat should not be used and > using unless is not desired. >
could you clarify ? style issues are easy, std if form... $stat is already used, it must contain extern to get here. checking it for a likely-linker-symbol seems fair.
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