71iq · Nov 7, 2026
diff --git a/src/pending_changes/edg-28967-deep-pointer-qualification.txt b/src/pending_changes/edg-28967-deep-pointer-qualification.txt
@@ -0,0 +1,16 @@
+[GH #455]
+GNU/Clang compatibility: unsafe multilevel pointer qualification conversions
+
+In GNU and Clang C++ modes, an implicit conversion between multilevel pointer
+types that adds const below the first level without adding it at every
+intermediate level (e.g., "char **" to "const char **") was accepted with a
+warning.  Such a conversion is not const-safe and is not a valid qualification
+conversion; GCC and Clang reject it.  It is now an error.  The qualification
+conversion changes for EDGcpfe/18553 are now also enabled for Clang 7.x and
+later, and the version check for MSVC 19.14 and later has been corrected.
+Conversions to arrays of unknown bound remain disabled for Clang versions
+before 14.  For example, with --g++:
+
+  void f(char **p) {
+    const char **q = p;  // Now an error.
+  }
diff --git a/src/types.c b/src/types.c
@@ -10989,16 +10989,17 @@ weird Microsoft-mode handling of the __unaligned and __restrict qualifiers).
         }  /* if */
         dest_type = pm_member_type(dest_type);
         source_type = pm_member_type(source_type);
-      } else if (!gpp_version_is(<80000) && !clang_mode &&
-                 !ms_version_is(>= 1914) &&
+      } else if (!gpp_version_is(<80000) && !clang_version_is(<70000) &&
+                 !ms_version_is(<1914) &&
                  is_array(source_type) && is_array(dest_type)) {
         /* N4261 reworked qualification conversions to include arrays (thereby
-           resolving Core issue 330).  GCC versions prior to 8.x, Clang, and
-           (some versions of) MSVC do not appear to implement that yet.
-           P0338R4 (in C++20) adjusted this further to allow conversions from
-           arrays with known bounds to arrays with unknown bounds. */
+           resolving Core issue 330).  Older emulated compilers do not
+           implement that.  P0388R4 (in C++20) adjusted this further to allow
+           conversions from arrays with known bounds to arrays with unknown
+           bounds. */
         if (!identical_array_type_level(source_type, dest_type) &&
-            !(cpp20_mode && !has_unknown_specified_bound(dest_type) &&
+            !(cpp20_mode && !clang_version_is(<140000) &&
+              !has_unknown_specified_bound(dest_type) &&
               dest_type->variant.array.variant.number_of_elements == 0)) {
           same = FALSE;
           break;
@@ -11384,6 +11385,7 @@ conversion in C++/CLI because it drops gc-ness of an interior_ptr.
 
 #endif /* MICROSOFT_EXTENSIONS_ALLOWED */
 
+
 a_boolean impl_pointer_conversion(
                          a_type_ptr           source_type,
                          a_boolean            source_is_constant,
@@ -11689,6 +11691,7 @@ operators), 3.3.15 (?: operator), and 3.3.16.1 (simple assignment).
           std_conv->warning_suggested = warning_suggested;
           qualifiers_checked = TRUE;
         } else if ((!suppress_extensions || any_cfront_mode()) &&
+                   !gpp_mode &&
                     same_type_with_added_qualifiers(
                            source_type_pointed_to,
                            dest_type_pointed_to,
@@ -11700,7 +11703,9 @@ operators), 3.3.15 (?: operator), and 3.3.16.1 (simple assignment).
              "int **" -> "const int **".  This is similar to the qualification
              conversion that is checked above, except that a few additional
              cases are accepted.  These are cases that are not const-safe,
-             so a warning is issued in most modes.  This is an extension. */
+             so a warning is issued in most modes.  This is an extension,
+             which is not provided in GNU and Clang modes since GCC and Clang
+             reject such conversions. */
           okay = TRUE;
           std_conv->nontrivial_conversion = FALSE;
           std_conv->type_qualifiers_added = qualifiers_added;

diff --git a/...ts/imported/clang/cpp/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/.p6.rto/default.1.1.txt b/...ts/imported/clang/cpp/CXX/dcl.dcl/dcl.spec/dcl.type/dcl.spec.auto/.p6.rto/default.1.1.txt
@@ -55,18 +55,14 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     const auto **fail2(p); // expected-error {{variable 'fail2' with type 'const auto **' has incompatible initializer of type 'int **'}}
           ^
 
-"Test_name.c", line 60: warning: a value of type "int **" cannot be used to initialize an entity of type "const int **"
+"Test_name.c", line 60: error: a value of type "int **" cannot be used to initialize an entity of type "const int **"
     const auto **fail2(p); // expected-error {{variable 'fail2' with type 'const auto **' has incompatible initializer of type 'int **'}}
                        ^
 
 "Test_name.c", line 60: warning: variable "p" is used before its value is set
     const auto **fail2(p); // expected-error {{variable 'fail2' with type 'const auto **' has incompatible initializer of type 'int **'}}
                        ^
 
-"Test_name.c", line 60: warning: variable "fail2" was declared but never referenced
-    const auto **fail2(p); // expected-error {{variable 'fail2' with type 'const auto **' has incompatible initializer of type 'int **'}}
-                 ^
-
 "Test_name.c", line 70: warning: "auto" as a type specifier is nonstandard in this mode
       auto p1 = &S::f;
       ^
@@ -123,4 +119,4 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
       int (*funcptr2)(int) = funcptr;
             ^
 
-4 errors detected in the compilation of "Test_name.c".
+5 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.1.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.1.1.txt
@@ -27,11 +27,7 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -59,4 +55,4 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-10 errors detected in the compilation of "Test_name.c".
+11 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.2.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.2.1.txt
@@ -37,11 +37,7 @@ fe_only -DTEST_NUMBER=2 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -92,4 +88,4 @@ fe_only -DTEST_NUMBER=2 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-14 errors detected in the compilation of "Test_name.c".
+15 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.3.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.3.1.txt
@@ -37,11 +37,7 @@ fe_only -DTEST_NUMBER=3 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -96,4 +92,4 @@ fe_only -DTEST_NUMBER=3 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-15 errors detected in the compilation of "Test_name.c".
+16 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.4.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.4.1.txt
@@ -27,11 +27,7 @@ fe_only -DTEST_NUMBER=4 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -102,4 +98,4 @@ fe_only -DTEST_NUMBER=4 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-17 errors detected in the compilation of "Test_name.c".
+18 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.5.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.5.1.txt
@@ -27,11 +27,7 @@ fe_only -DTEST_NUMBER=5 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -152,4 +148,4 @@ fe_only -DTEST_NUMBER=5 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-20 errors detected in the compilation of "Test_name.c".
+21 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.6.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.6.1.txt
@@ -27,11 +27,7 @@ fe_only -DTEST_NUMBER=6 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -152,4 +148,4 @@ fe_only -DTEST_NUMBER=6 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-20 errors detected in the compilation of "Test_name.c".
+21 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.7.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg23xx.rto/default.7.1.txt
@@ -27,11 +27,7 @@ fe_only -DTEST_NUMBER=7 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     int *const *const &f2() { return p; }
                                      ^
 
-"Test_name.c", line 261: warning: return value type does not match the function type
-    const int **const &f4() { return p; }
-                                     ^
-
-"Test_name.c", line 261: warning: returning reference to local temporary
+"Test_name.c", line 261: error: return value type does not match the function type
     const int **const &f4() { return p; }
                                      ^
 
@@ -152,4 +148,4 @@ fe_only -DTEST_NUMBER=7 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
   const A a;
           ^
 
-20 errors detected in the compilation of "Test_name.c".
+21 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.1.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.1.1.txt
@@ -177,14 +177,6 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                            ^
           detected during instantiation of class "cwg329::A<T> [with T=int]" at line 453
 
-"Test_name.c", line 467: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q" (aka "const int *const (*)[3]")
-      q = p; // ok
-        ^
-
-"Test_name.c", line 468: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q2" (aka "const cwg330::Qinner *")
-      q2 = p; // ok
-         ^
-
 "Test_name.c", line 469: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::R" (aka "const int *const (*)[4]")
       r = p;
         ^
@@ -789,7 +781,7 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                               ^
           detected during instantiation of "void cwg345::f(T) [with T=cwg345::A]" at line 753
 
-"Test_name.c", line 787: warning: return value type does not match the function type
+"Test_name.c", line 787: error: return value type does not match the function type
         return p;
                ^
           detected during instantiation of "cwg349::A::operator T ***() [with T=const int]" at line 796
@@ -849,4 +841,4 @@ fe_only -DTEST_NUMBER=1 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     const A b(a);
             ^
 
-154 errors detected in the compilation of "Test_name.c".
+155 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.2.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.2.1.txt
@@ -169,14 +169,6 @@ fe_only -DTEST_NUMBER=2 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                            ^
           detected during instantiation of class "cwg329::A<T> [with T=int]" at line 453
 
-"Test_name.c", line 467: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q" (aka "const int *const (*)[3]")
-      q = p; // ok
-        ^
-
-"Test_name.c", line 468: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q2" (aka "const cwg330::Qinner *")
-      q2 = p; // ok
-         ^
-
 "Test_name.c", line 469: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::R" (aka "const int *const (*)[4]")
       r = p;
         ^
@@ -751,7 +743,7 @@ fe_only -DTEST_NUMBER=2 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                               ^
           detected during instantiation of "void cwg345::f(T) [with T=cwg345::A]" at line 753
 
-"Test_name.c", line 787: warning: return value type does not match the function type
+"Test_name.c", line 787: error: return value type does not match the function type
         return p;
                ^
           detected during instantiation of "cwg349::A::operator T ***() [with T=const int]" at line 796
@@ -831,4 +823,4 @@ fe_only -DTEST_NUMBER=2 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     extern WithoutLinkage5 withoutLinkage5;
                            ^
 
-155 errors detected in the compilation of "Test_name.c".
+156 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.3.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.3.1.txt
@@ -165,14 +165,6 @@ fe_only -DTEST_NUMBER=3 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                            ^
           detected during instantiation of class "cwg329::A<T> [with T=int]" at line 453
 
-"Test_name.c", line 467: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q" (aka "const int *const (*)[3]")
-      q = p; // ok
-        ^
-
-"Test_name.c", line 468: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q2" (aka "const cwg330::Qinner *")
-      q2 = p; // ok
-         ^
-
 "Test_name.c", line 469: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::R" (aka "const int *const (*)[4]")
       r = p;
         ^
@@ -743,7 +735,7 @@ fe_only -DTEST_NUMBER=3 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                               ^
           detected during instantiation of "void cwg345::f(T) [with T=cwg345::A]" at line 753
 
-"Test_name.c", line 787: warning: return value type does not match the function type
+"Test_name.c", line 787: error: return value type does not match the function type
         return p;
                ^
           detected during instantiation of "cwg349::A::operator T ***() [with T=const int]" at line 796
@@ -823,4 +815,4 @@ fe_only -DTEST_NUMBER=3 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     extern WithoutLinkage5 withoutLinkage5;
                            ^
 
-155 errors detected in the compilation of "Test_name.c".
+156 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.4.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.4.1.txt
@@ -161,14 +161,6 @@ fe_only -DTEST_NUMBER=4 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                            ^
           detected during instantiation of class "cwg329::A<T> [with T=int]" at line 453
 
-"Test_name.c", line 467: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q" (aka "const int *const (*)[3]")
-      q = p; // ok
-        ^
-
-"Test_name.c", line 468: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q2" (aka "const cwg330::Qinner *")
-      q2 = p; // ok
-         ^
-
 "Test_name.c", line 469: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::R" (aka "const int *const (*)[4]")
       r = p;
         ^
@@ -739,7 +731,7 @@ fe_only -DTEST_NUMBER=4 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                               ^
           detected during instantiation of "void cwg345::f(T) [with T=cwg345::A]" at line 753
 
-"Test_name.c", line 787: warning: return value type does not match the function type
+"Test_name.c", line 787: error: return value type does not match the function type
         return p;
                ^
           detected during instantiation of "cwg349::A::operator T ***() [with T=const int]" at line 796
@@ -819,4 +811,4 @@ fe_only -DTEST_NUMBER=4 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
     extern WithoutLinkage5 withoutLinkage5;
                            ^
 
-155 errors detected in the compilation of "Test_name.c".
+156 errors detected in the compilation of "Test_name.c".
diff --git a/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.5.1.txt b/tests/tests/imported/clang/cpp/CXX/drs/.cwg3xx.rto/default.5.1.txt
@@ -161,22 +161,10 @@ fe_only -DTEST_NUMBER=5 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                            ^
           detected during instantiation of class "cwg329::A<T> [with T=int]" at line 453
 
-"Test_name.c", line 467: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q" (aka "const int *const (*)[3]")
-      q = p; // ok
-        ^
-
-"Test_name.c", line 468: warning: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::Q2" (aka "const cwg330::Qinner *")
-      q2 = p; // ok
-         ^
-
 "Test_name.c", line 469: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::R" (aka "const int *const (*)[4]")
       r = p;
         ^
 
-"Test_name.c", line 471: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::S" (aka "const int *const (*)[]")
-      s = p;
-        ^
-
 "Test_name.c", line 473: error: a value of type "cwg330::P" (aka "int *(*)[3]") cannot be assigned to an entity of type "cwg330::T" (aka "const int *(*)[]")
       t = p;
         ^
@@ -739,7 +727,7 @@ fe_only -DTEST_NUMBER=5 --clang -tused -e 200 --no_wrap_diagnostics --clang_vers
                                               ^
           detected during instantiation of "void cwg345::f(T) [with T=cwg345::A]" at line 753
 
-"Test_name.c", line 787: warning: return value type does not match the function type
+"Test_name.c", line 787: error: return value type does not match the function type
         return p;
                ^
           detected during instantiation of "cwg349::A::operator T ***() [with T=const int]" at line 796