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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c++/51350] New: [4.7 Regression] Bogus -Wstrict-overflow warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false Date: Tue, 29 Nov 2011 22:57:00 -0000 [thread overview] Message-ID: <bug-51350-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51350 Bug #: 51350 Summary: [4.7 Regression] Bogus -Wstrict-overflow warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false Classification: Unclassified Product: gcc Version: 4.7.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned@gcc.gnu.org ReportedBy: burnus@gcc.gnu.org Host: x86_64-unknown-linux-gnu When compiling the following code with g++ -Wall -O2 test.cc, one gets with GCC 4.7.0 20111129. [GCC 4.6.2 does not print a warning.] test.cc:9:3: Warnung: assuming signed overflow does not occur when assuming that (X + c) < X is always false [-Wstrict-overflow] However, I fail to see why one has (X + c) < X for the general case; it should only occur if (start >= pattern_length), but as the value for "start" is not known at compile time ... void PopulateBoyerMooreTable(int pattern_length, int start, int * shift_table, int* suffix_table, int length) { int suffix = pattern_length + 1; int i = pattern_length; while (i > start) suffix_table[--i] = --suffix; if (suffix < pattern_length) for (int j = start; j <= pattern_length; j++) shift_table[j] = suffix - start; } Original file: http://code.google.com/p/v8/source/browse/branches/bleeding_edge/src/string-search.h#150
next reply other threads:[~2011-11-29 22:41 UTC|newest] Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-11-29 22:57 burnus at gcc dot gnu.org [this message] 2011-12-05 14:12 ` [Bug c++/51350] " rguenth at gcc dot gnu.org 2011-12-05 15:17 ` rguenth at gcc dot gnu.org
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