[Clang] Warning as error Array Comparisons from C++26 (#118872)

Starting from C++26 the array comparison warning should converted to an error. Fixes: #117859
2024-12-07 18:28:09 +01:00
parent 342c8db381
commit 3f458cd9ab
8 changed files with 24 additions and 9 deletions
--- a/clang-tools-extra/test/clang-tidy/checkers/misc/redundant-expression.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/redundant-expression.cpp
@@ -1,4 +1,4 @@
-// RUN: %check_clang_tidy %s misc-redundant-expression %t -- -- -fno-delayed-template-parsing
+// RUN: %check_clang_tidy %s misc-redundant-expression %t -- -- -fno-delayed-template-parsing -Wno-array-compare-cxx26

 typedef __INT64_TYPE__ I64;

--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -428,6 +428,9 @@ New Compiler Flags
 - The ``-Warray-compare`` warning has been added to warn about array comparison
  on versions older than C++20.

+- The ``-Warray-compare-cxx26`` warning has been added to warn about array comparison
+  starting from C++26, this warning is enabled as an error by default.
+
 Deprecated Compiler Flags
 -------------------------

--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -10274,6 +10274,11 @@ def warn_array_comparison : Warning<
  "to compare array addresses, use unary '+' to decay operands to pointers">,
  InGroup<DiagGroup<"array-compare">>;

+def warn_array_comparison_cxx26 : Warning<
+  "comparison between two arrays is ill-formed in C++26; "
+  "to compare array addresses, use unary '+' to decay operands to pointers">,
+  InGroup<DiagGroup<"array-compare-cxx26">>, DefaultError;
+
 def warn_stringcompare : Warning<
  "result of comparison against %select{a string literal|@encode}0 is "
  "unspecified (use an explicit string comparison function instead)">,
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -11843,7 +11843,9 @@ static void diagnoseTautologicalComparison(Sema &S, SourceLocation Loc,
      RHSStripped->getType()->isArrayType()) {
    auto IsDeprArrayComparionIgnored =
        S.getDiagnostics().isIgnored(diag::warn_depr_array_comparison, Loc);
-    auto DiagID = !S.getLangOpts().CPlusPlus20 || IsDeprArrayComparionIgnored
+    auto DiagID = S.getLangOpts().CPlusPlus26
+                      ? diag::warn_array_comparison_cxx26
+                  : !S.getLangOpts().CPlusPlus20 || IsDeprArrayComparionIgnored
                      ? diag::warn_array_comparison
                      : diag::warn_depr_array_comparison;
    S.Diag(Loc, DiagID) << LHS->getSourceRange() << RHS->getSourceRange()
--- a/clang/test/Sema/warn-stringcompare.c
+++ b/clang/test/Sema/warn-stringcompare.c
@@ -1,5 +1,6 @@
 // RUN: %clang_cc1 -x c -fsyntax-only -verify %s
 // RUN: %clang_cc1 -x c++ -fsyntax-only -verify=expected,cxx %s
+// RUN: %clang_cc1 -x c++ -std=c++26 -fsyntax-only -verify=expected,cxx26 %s

 #define DELIM "/"
 #define DOT "."
@@ -15,15 +16,15 @@ void test(const char *d) {
  if (NULL == "/")
    return;
  if ("/" != DELIM) // expected-warning {{result of comparison against a string literal is unspecified (use an explicit string comparison function instead)}}
-    return;         // cxx-warning@-1 {{comparison between two arrays}}
+    return;         // cxx-warning@-1 {{comparison between two arrays}} cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
  if (DELIM == "/") // expected-warning {{result of comparison against a string literal is unspecified (use an explicit string comparison function instead)}}
-    return;         // cxx-warning@-1 {{comparison between two arrays}}
+    return;         // cxx-warning@-1 {{comparison between two arrays}} cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
  if (DELIM != NULL)
    return;
  if (NULL == DELIM)
    return;
  if (DOT != DELIM) // expected-warning {{result of comparison against a string literal is unspecified (use an explicit string comparison function instead)}}
-    return;         // cxx-warning@-1 {{comparison between two arrays}}
+    return;         // cxx-warning@-1 {{comparison between two arrays}} cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
  if (DELIM == DOT) // expected-warning {{result of comparison against a string literal is unspecified (use an explicit string comparison function instead)}}
-    return;         // cxx-warning@-1 {{comparison between two arrays}}
+    return;         // cxx-warning@-1 {{comparison between two arrays}} cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
 }
--- a/clang/test/SemaCXX/warn-array-comparion.cpp
+++ b/clang/test/SemaCXX/warn-array-comparion.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s -verify=expected,not-cxx20
 // RUN: %clang_cc1 -std=c++20 -fsyntax-only -Wno-deprecated-array-compare -verify %s -verify=expected,not-cxx20
 // RUN: %clang_cc1 -std=c++20 -fsyntax-only -Wdeprecated -verify %s -verify=expected,cxx20
+// RUN: %clang_cc1 -std=c++26 -fsyntax-only -Wdeprecated -verify %s -verify=expected,cxx26

 typedef struct {
  char str[16];
@@ -9,13 +10,14 @@ typedef struct {

 bool object_equal(const Object &obj1, const Object &obj2) {
  if (obj1.str != obj2.str) // not-cxx20-warning {{comparison between two arrays compare their addresses}} cxx20-warning {{comparison between two arrays is deprecated}}
-    return false;
+    return false;           // cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
  if (obj1.id != obj2.id) // not-cxx20-warning {{comparison between two arrays compare their addresses}} cxx20-warning {{comparison between two arrays is deprecated}}
-    return false;
+    return false;         // cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
  return true;
 }


 void foo(int (&array1)[2], int (&array2)[2]) {
  if (array1 == array2) { } // not-cxx20-warning {{comparison between two arrays compare their addresses}} cxx20-warning {{comparison between two arrays is deprecated}}
+                            // cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
 }
--- a/clang/test/SemaCXX/warn-self-comparisons.cpp
+++ b/clang/test/SemaCXX/warn-self-comparisons.cpp
@@ -1,6 +1,8 @@
 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s -verify=expected,not-cxx20
 // RUN: %clang_cc1 -std=c++20 -fsyntax-only -Wdeprecated -verify %s -verify=expected,cxx20
+// RUN: %clang_cc1 -std=c++26 -fsyntax-only -Wdeprecated -verify %s -verify=expected,cxx26

 void f(int (&array1)[2], int (&array2)[2]) {
  if (array1 == array2) { } // not-cxx20-warning {{comparison between two arrays compare their addresses}} cxx20-warning {{comparison between two arrays is deprecated}}
+                            // cxx26-error@-1 {{comparison between two arrays is ill-formed in C++26}}
 }
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -239,7 +239,7 @@ C++23, informally referred to as C++26.</p>
 <tr>
  <td>Remove Deprecated Array Comparisons from C++26</td>
  <td><a href="https://wg21.link/P2865R6">P2865R6</a></td>
-  <td class="none" align="center">No</td>
+  <td class="unreleased" align="center">Clang 20</td>
 </tr>
 <tr>
  <td>Structured Bindings can introduce a Pack</td>