[PATCH] D141310: [clang] add -Wcompare-function-pointers

[Adrian Dole via Phabricator via cfe-commits]

adriandole updated this revision to Diff 489109.
adriandole added a comment.

- More helpful diagnostic message.
- Check variable and type names are printed in tests.
- Enable `-Wordered-function-pointer-comparison` when this warning is enabled.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141310/new/

https://reviews.llvm.org/D141310

Files:
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Sema/SemaExpr.cpp
  clang/test/SemaCXX/compare-function-pointer.cpp


Index: clang/test/SemaCXX/compare-function-pointer.cpp
===================================================================
--- clang/test/SemaCXX/compare-function-pointer.cpp
+++ clang/test/SemaCXX/compare-function-pointer.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify -Wcompare-function-pointers %s
 
 using fp0_t = void (*)();
 using fp1_t = int (*)();
@@ -6,8 +6,8 @@
 extern fp0_t a, b;
 extern fp1_t c;
 
-bool eq0 = a == b;
-bool ne0 = a != b;
+bool eq0 = a == b;  // expected-warning {{distinct function pointers ('fp0_t' (aka 'void (*)()') and 'fp0_t')}}
+bool ne0 = a != b;  // expected-warning {{distinct function pointers}}
 bool lt0 = a < b;   // expected-warning {{ordered comparison of function pointers ('fp0_t' (aka 'void (*)()') and 'fp0_t')}}
 bool le0 = a <= b;  // expected-warning {{ordered comparison of function pointers}}
 bool gt0 = a > b;   // expected-warning {{ordered comparison of function pointers}}
@@ -15,7 +15,9 @@
 auto tw0 = a <=> b; // expected-error {{ordered comparison of function pointers}}
 
 bool eq1 = a == c;  // expected-error {{comparison of distinct pointer types}}
+                    // expected-warning at -1 {{distinct function pointers ('fp0_t' (aka 'void (*)()') and 'fp1_t' (aka 'int (*)()'))}}
 bool ne1 = a != c;  // expected-error {{comparison of distinct pointer types}}
+                    // expected-warning at -1 {{distinct function pointers}}
 bool lt1 = a < c;   // expected-warning {{ordered comparison of function pointers ('fp0_t' (aka 'void (*)()') and 'fp1_t' (aka 'int (*)()'))}}
                     // expected-error at -1 {{comparison of distinct pointer types}}
 bool le1 = a <= c;  // expected-warning {{ordered comparison of function pointers}}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -12711,6 +12711,12 @@
                                    LHS.get()->getSourceRange());
   }
 
+  if (!IsOrdered && LHSType->isFunctionPointerType() &&
+      RHSType->isFunctionPointerType() && !LHSIsNull && !RHSIsNull)
+    Diag(Loc, diag::warn_typecheck_comparison_of_function_pointers)
+          << LHSType << RHSType
+          << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
+
   if (IsOrdered && LHSType->isFunctionPointerType() &&
       RHSType->isFunctionPointerType()) {
     // Valid unless a relational comparison of function pointers
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -7009,6 +7009,10 @@
   "%0 is %select{|in}2complete and "
   "%1 is %select{|in}3complete">,
   InGroup<C11>;
+def warn_typecheck_comparison_of_function_pointers : Warning<
+  "distinct function pointers (%0 and %1) may compare equal "
+  "when using identical code folding">,
+  InGroup<CompareFunctionPointers>, DefaultIgnore;
 def warn_typecheck_ordered_comparison_of_function_pointers : Warning<
   "ordered comparison of function pointers (%0 and %1)">,
   InGroup<OrderedCompareFunctionPointers>;
Index: clang/include/clang/Basic/DiagnosticGroups.td
===================================================================
--- clang/include/clang/Basic/DiagnosticGroups.td
+++ clang/include/clang/Basic/DiagnosticGroups.td
@@ -564,6 +564,7 @@
 def DeprecatedObjCIsaUsage : DiagGroup<"deprecated-objc-isa-usage">;
 def ExplicitInitializeCall : DiagGroup<"explicit-initialize-call">;
 def OrderedCompareFunctionPointers : DiagGroup<"ordered-compare-function-pointers">;
+def CompareFunctionPointers : DiagGroup<"compare-function-pointers", [OrderedCompareFunctionPointers]>;
 def PackedNonPod : DiagGroup<"packed-non-pod">;
 def Packed : DiagGroup<"packed", [PackedNonPod]>;
 def Padded : DiagGroup<"padded">;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -455,6 +455,8 @@
 - Add ``-Wreturn-local-addr``, a GCC alias for ``-Wreturn-stack-address``.
 - Clang now suppresses ``-Wlogical-op-parentheses`` on ``(x && a || b)`` and ``(a || b && x)``
   only when ``x`` is a string literal.
+- Add ``-Wcompare-function-pointers`` to warn about comparisons that may have their behavior
+  change when enabling the identical code folding optimization feature of some linkers.
 
 Non-comprehensive list of changes in this release
 -------------------------------------------------


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