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* [Sema] Fixes for enum handling for tautological comparison diagnosticsRoman Lebedev2017-10-211-14/+206
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Summary: As Mattias Eriksson has reported in PR35009, in C, for enums, the underlying type should be used when checking for the tautological comparison, unlike C++, where the enumerator values define the value range. So if not in CPlusPlus mode, use the enum underlying type. Also, i have discovered a problem (a crash) when evaluating tautological-ness of the following comparison: ``` enum A { A_a = 0 }; if (a < 0) // expected-warning {{comparison of unsigned enum expression < 0 is always false}} return 0; ``` This affects both the C and C++, but after the first fix, only C++ code was affected. That was also fixed, while preserving (i think?) the proper diagnostic output. And while there, attempt to enhance the test coverage. Yes, some tests got moved around, sorry about that :) Fixes PR35009 Reviewers: aaron.ballman, rsmith, rjmccall Reviewed By: aaron.ballman Subscribers: Rakete1111, efriedma, materi, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D39122 llvm-svn: 316268
* Replace r313747, don't always warn on enums, rework testcases.Roman Lebedev2017-09-201-3/+25
| | | | | | | | | | | | | As Aaron Ballman has pointed out, that is not really correct. So the key problem there is the invalidity of the testcase. Revert r313747, and rework testcase in such a way, so these details (platform-specific default enum sigdness) are accounted for. Also, add a C++-specific testcase. llvm-svn: 313756
* [Sema] Move some stuff into -Wtautological-unsigned-enum-zero-compareRoman Lebedev2017-09-201-0/+46
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Recommit. Original commit was reverted because buildbots broke. The error was only reproducible in the build with assertions. The problem was that the diagnostic expected true/false as bool, while it was provided as string "true"/"false". Summary: As requested by Sam McCall: > Enums (not new I guess). Typical case: if (enum < 0 || enum > MAX) > The warning strongly suggests that the enum < 0 check has no effect > (for enums with nonnegative ranges). > Clang doesn't seem to optimize such checks out though, and they seem > likely to catch bugs in some cases. Yes, only if there's UB elsewhere, > but I assume not optimizing out these checks indicates a deliberate > decision to stay somewhat compatible with a technically-incorrect > mental model. > If this is the case, should we move these to a > -Wtautological-compare-enum subcategory? Reviewers: rjmccall, rsmith, aaron.ballman, sammccall, bkramer, djasper Reviewed By: aaron.ballman Subscribers: jroelofs, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D37629 llvm-svn: 313745
* Revert "[Sema] Move some stuff into -Wtautological-unsigned-enum-zero-compare"Roman Lebedev2017-09-191-46/+0
| | | | | | | | | | | | | | | | This reverts commit r313677. Buildbots fail with assertion failure Failing Tests (7): Clang :: Analysis/null-deref-ps.c Clang :: CodeGen/enum.c Clang :: Sema/compare.c Clang :: Sema/outof-range-constant-compare.c Clang :: Sema/tautological-unsigned-enum-zero-compare.c Clang :: Sema/tautological-unsigned-zero-compare.c Clang :: SemaCXX/compare.cpp llvm-svn: 313683
* [Sema] Move some stuff into -Wtautological-unsigned-enum-zero-compareRoman Lebedev2017-09-191-0/+46
Summary: As requested by Sam McCall: > Enums (not new I guess). Typical case: if (enum < 0 || enum > MAX) > The warning strongly suggests that the enum < 0 check has no effect > (for enums with nonnegative ranges). > Clang doesn't seem to optimize such checks out though, and they seem > likely to catch bugs in some cases. Yes, only if there's UB elsewhere, > but I assume not optimizing out these checks indicates a deliberate > decision to stay somewhat compatible with a technically-incorrect > mental model. > If this is the case, should we move these to a > -Wtautological-compare-enum subcategory? Reviewers: rjmccall, rsmith, aaron.ballman, sammccall, bkramer, djasper Reviewed By: aaron.ballman Subscribers: jroelofs, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D37629 llvm-svn: 313677
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