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llvm-project/clang/test/SemaCXX/warn-bitwise-compare.cpp

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New tautological warning for bitwise-or with non-zero constant always true. Taking a value and the bitwise-or it with a non-zero constant will always result in a non-zero value. In a boolean context, this is always true. if (x | 0x4) {} // always true, intended '&' This patch creates a new warning group -Wtautological-bitwise-compare for this warning. It also moves in the existing tautological bitwise comparisons into this group. A few other changes were needed to the CFGBuilder so that all bool contexts would be checked. The warnings in -Wtautological-bitwise-compare will be off by default due to using the CFG. Fixes: https://bugs.llvm.org/show_bug.cgi?id=42666 Differential Revision: https://reviews.llvm.org/D66046 llvm-svn: 375318
2019-10-19 08:57:23 +08:00
// RUN: %clang_cc1 -fsyntax-only -verify -Wtautological-bitwise-compare %s
Add -Wtautological-compare to -Wall Some warnings in -Wtautological-compare subgroups are DefaultIgnore. Adding this group to -Wmost, which is part of -Wall, will aid in their discoverability. Differential Revision: https://reviews.llvm.org/D69292
2019-11-13 05:46:03 +08:00
// RUN: %clang_cc1 -fsyntax-only -verify -Wall -Wno-unused %s
New tautological warning for bitwise-or with non-zero constant always true. Taking a value and the bitwise-or it with a non-zero constant will always result in a non-zero value. In a boolean context, this is always true. if (x | 0x4) {} // always true, intended '&' This patch creates a new warning group -Wtautological-bitwise-compare for this warning. It also moves in the existing tautological bitwise comparisons into this group. A few other changes were needed to the CFGBuilder so that all bool contexts would be checked. The warnings in -Wtautological-bitwise-compare will be off by default due to using the CFG. Fixes: https://bugs.llvm.org/show_bug.cgi?id=42666 Differential Revision: https://reviews.llvm.org/D66046 llvm-svn: 375318
2019-10-19 08:57:23 +08:00
void test(int x) {
bool b1 = (8 & x) == 3;
// expected-warning@-1 {{bitwise comparison always evaluates to false}}
bool b2 = x | 5;
// expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
bool b3 = (x | 5);
// expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
bool b4 = !!(x | 5);
// expected-warning@-1 {{bitwise or with non-zero value always evaluates to true}}
}