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Date: Thu, 12 Nov 2015 09:54:55 +0900 From: Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> To: David Rientjes <rientjes@...gle.com> Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, Christoph Lameter <cl@...ux.com>, Pekka Enberg <penberg@...nel.org>, Joonsoo Kim <iamjoonsoo.kim@....com>, linux-mm@...ck.org, linux-kernel@...r.kernel.org, Sergey Senozhatsky <sergey.senozhatsky.work@...il.com> Subject: Re: [PATCH 2/3] tools/vm/page-types: suppress gcc warnings On (11/11/15 12:44), David Rientjes wrote: [..] > This can't possibly be correct, the warnings are legitimate and the result > of the sigsetjmp() in the function. You may be interested in > returns_twice rather than marking random automatic variables as volatile. Hm, ok. I saw no probs with `int first' and `end' being volatile static void walk_file(const char *name, const struct stat *st) { int first = 1; for (...) { if (sigsetjmp(sigbus_jmp, 1)) { goto got_sigbus; } got_sigbus: ... if (first && opt_list) { first = 0; print_foo(); } } } the `end' is also looked fine. ANSI C ยง7.13.2.1 3 All accessible objects have values, and all other components of the abstract machine 249) have state, as of the time the longjmp function was called, except that the values of objects of automatic storage duration that are local to the function containing the invocation of the corresponding setjmp macro that do not have volatile-qualified type ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ and have been changed between the setjmp invocation and longjmp call are indeterminate. Thus, adding 'volatile' should do the trick. Isn't it? I need to google more - is returns_twice actually prevents gcc from `over-optimizing' (there are some bug reports that state that setjmp can be screwed up by gcc) or it's actually because the programs that do setjmp basically violate ANSI C standard and don't volatile-qualify the affected variables. Any hint would be helpful. -ss -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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