Author: Richard Smith Date: 2020-08-31T23:16:48-07:00 New Revision: f819dbf012b3f624a836641f90dabff5f667b82e
URL: https://github.com/llvm/llvm-project/commit/f819dbf012b3f624a836641f90dabff5f667b82e DIFF: https://github.com/llvm/llvm-project/commit/f819dbf012b3f624a836641f90dabff5f667b82e.diff LOG: Classify (small unsigned bitfield) < 0 comparisons under -Wtautological-unsigned-zero-compare not under -Wtautological-value-range-compare. Added: Modified: clang/lib/Sema/SemaChecking.cpp clang/test/Sema/compare.c Removed: ################################################################################ diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp index 3a2f070e7e68..2e07c8f63b79 100644 --- a/clang/lib/Sema/SemaChecking.cpp +++ b/clang/lib/Sema/SemaChecking.cpp @@ -10944,6 +10944,12 @@ static bool CheckTautologicalComparison(Sema &S, BinaryOperator *E, if (InRange && IsEnumConstOrFromMacro(S, Constant)) return false; + // A comparison of an unsigned bit-field against 0 is really a type problem, + // even though at the type level the bit-field might promote to 'signed int'. + if (Other->refersToBitField() && InRange && Value == 0 && + Other->getType()->isUnsignedIntegerOrEnumerationType()) + TautologicalTypeCompare = true; + // If this is a comparison to an enum constant, include that // constant in the diagnostic. const EnumConstantDecl *ED = nullptr; diff --git a/clang/test/Sema/compare.c b/clang/test/Sema/compare.c index 25aa13f6ba38..85dcffc502fd 100644 --- a/clang/test/Sema/compare.c +++ b/clang/test/Sema/compare.c @@ -285,6 +285,20 @@ int test5(unsigned int x) { && (0 <= x); // expected-warning {{comparison of 0 <= unsigned expression is always true}} } +struct bitfield { + int a : 3; + unsigned b : 3; + long c : 40; + unsigned long d : 40; +}; + +void test5a(struct bitfield a) { + if (a.a < 0) {} + if (a.b < 0) {} // expected-warning {{comparison of unsigned expression < 0 is always false}} + if (a.c < 0) {} + if (a.d < 0) {} // expected-warning {{comparison of unsigned expression < 0 is always false}} +} + int test6(unsigned i, unsigned power) { unsigned x = (i < (1 << power) ? i : 0); return x != 3 ? 1 << power : i; _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
