[gcc r16-9321] c++: implement CWG3020 - Missing specification for __has_cpp_attribute(indeterminate) [PR126309]

https://gcc.gnu.org/g:13631c446806527c9aad99c3d2c1536c1c950cd1

commit r16-9321-g13631c446806527c9aad99c3d2c1536c1c950cd1
Author: Jakub Jelinek <[email protected]>
Date:   Mon Jul 20 23:32:40 2026 +0200

    c++: implement CWG3020 - Missing specification for __has_cpp_attribute(indeterminate) [PR126309]
    
    The paper which introduced indeterminate attribute has not added a value
    for __has_cpp_attribute, so I've missed it and didn't add it to
    c_common_has_attribute.  Later CWG issue fixed this up.
    
    2026-07-20  Jakub Jelinek  <[email protected]>
    
            PR c++/126309
            * c-lex.cc: Implement CWG3020 - Missing specification for
            __has_cpp_attribute(indeterminate).
            (c_common_has_attribute): Handle __has_cpp_attribute (indeterminate).
    
            * g++.dg/cpp26/feat-cxx26.C: Test __has_cpp_attribute (indeterminate).
    
    Reviewed-by: Jason Merrill <[email protected]>
    (cherry picked from commit 71a5a83ea92f4cde1ca2b37f3b160353a729f35b)

Diff:
---
 gcc/c-family/c-lex.cc                   |  2 ++
 gcc/testsuite/g++.dg/cpp26/feat-cxx26.C | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/gcc/c-family/c-lex.cc b/gcc/c-family/c-lex.cc
index 1750fbc3d062..09fbbdd22562 100644
--- a/gcc/c-family/c-lex.cc
+++ b/gcc/c-family/c-lex.cc
@@ -433,6 +433,8 @@ c_common_has_attribute (cpp_reader *pfile, bool std_syntax)
 		result = 201907;
 	      else if (is_attribute_p ("assume", attr_name))
 		result = 202207;
+	      else if (is_attribute_p ("indeterminate", attr_name))
+		result = 202403;
 	      else if (is_attribute_p ("init_priority", attr_name))
 		{
 		  /* The (non-standard) init_priority attribute is always
diff --git a/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C b/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C
index 248116699617..66b3cd7ceecb 100644
--- a/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C
+++ b/gcc/testsuite/g++.dg/cpp26/feat-cxx26.C
@@ -652,3 +652,15 @@
 #elif __cpp_expansion_statements != 202506
 #  error "__cpp_expansion_statements != 202506"
 #endif
+
+// C++26 attributes:
+
+#ifdef __has_cpp_attribute
+#  if ! __has_cpp_attribute(indeterminate)
+#    error "__has_cpp_attribute(indeterminate)"
+#  elif __has_cpp_attribute(indeterminate) != 202403
+#    error "__has_cpp_attribute(indeterminate) != 202403"
+#  endif
+#else
+#  error "__has_cpp_attribute"
+#endif