[PATCH] D51545: Enable -Wtautological-unsigned-zero-compare under -Wextra

Elizabeth Andrews via Phabricator via cfe-commits cfe-commits at lists.llvm.org
Fri Aug 31 08:51:38 PDT 2018

eandrews created this revision.
eandrews added reviewers: lebedev.ri, rsmith, rjmccall, rnk, mclow.lists, erichkeane.

GCC enables -Wtype-limits under -Wextra. Warnings under GCC's -Wtype-limits is covered in Clang by -Wtautological-type-limit-compare and -Wtautological-unsigned-zero-compare.

Since -Wtautological-type-limit-compare can fire spuriously when a type's size is platform-dependent (as detailed in D41512 <https://reviews.llvm.org/D41512>), I am adding only -Wtautological-unsigned-zero-compare to -Wextra.

I should point out that GCC does not throw warnings on pointless unsigned expression comparisons inside templates while -Wtautological-unsigned-zero-compare does. I figure this is a limitation in GCC's implementation and don't think this is an issue but please feel free to let me know if I am mistaken.



Index: test/Sema/tautological-unsigned-zero-compare.c
--- test/Sema/tautological-unsigned-zero-compare.c
+++ test/Sema/tautological-unsigned-zero-compare.c
@@ -8,6 +8,12 @@
 // RUN:            -verify -x c++ %s
 // RUN: %clang_cc1 -fsyntax-only \
 // RUN:            -verify=silence -x c++ %s
+// RUN: %clang_cc1 -fsyntax-only \
+// RUN:            -Wextra -Wno-sign-compare\
+// RUN:            -verify %s
+// RUN: %clang_cc1 -fsyntax-only \
+// RUN:            -Wextra -Wno-sign-compare\
+// RUN:            -verify -x c++ %s
 unsigned uvalue(void);
 signed int svalue(void);
Index: include/clang/Basic/DiagnosticGroups.td
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -763,7 +763,8 @@
-    NullPointerArithmetic
+    NullPointerArithmetic,
+    TautologicalUnsignedZeroCompare
 def Most : DiagGroup<"most", [

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