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From: "vincent-gcc at vinc17 dot net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug analyzer/98447] incorrect -Wanalyzer-shift-count-overflow warning Date: Sat, 26 Dec 2020 18:17:04 +0000 [thread overview] Message-ID: <bug-98447-4-5SSFcbHwfG@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-98447-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98447 --- Comment #2 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- Note: The warning occurs when the compiler knows that b < 63 in the "if" case (it occurs up to "n = r % 64", but not with "n = r % 65") so that the condition "b + 1 >= 64" is always false. I suppose that the p[i--] line has already been simplified to something equivalent to p[i--] = 1UL << (b + 1); but the analyzer doesn't see that b has restricted values in the "if" case. if (n > b) { p[i--] = 1UL << (b + 1); b += 64; } triggers the warning, but not if (63 > b) { p[i--] = 1UL << (b + 1); b += 64; }
next prev parent reply other threads:[~2020-12-26 18:17 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-12-26 0:51 [Bug analyzer/98447] New: " vincent-gcc at vinc17 dot net 2020-12-26 16:35 ` [Bug analyzer/98447] " vincent-gcc at vinc17 dot net 2020-12-26 18:17 ` vincent-gcc at vinc17 dot net [this message] 2020-12-26 18:21 ` vincent-gcc at vinc17 dot net 2020-12-26 18:47 ` vincent-gcc at vinc17 dot net 2021-01-29 13:50 ` vincent-gcc at vinc17 dot net 2021-04-21 11:54 ` vincent-gcc at vinc17 dot net 2023-02-28 12:59 ` vincent-gcc at vinc17 dot net
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