https://gcc.gnu.org/g:a088603cbbaa2a8ffad2551ca9490045eb415e25

commit r16-6363-ga088603cbbaa2a8ffad2551ca9490045eb415e25
Author: lenny.chiadmi-delage <[email protected]>
Date:   Fri Dec 19 12:34:45 2025 +0000

    gccrs: respect cfg_attr expansion
    
    Fix cfg_attr expansion and feature gate attribute handling
    
    Fixes Rust-GCC#4245
    
    gcc/rust/ChangeLog:
    
            * checks/errors/feature/rust-feature-gate.cc (FeatureGate::visit): 
Added
            handling for META_ITEM type attributes to properly process feature 
gates.
            * expand/rust-cfg-strip.cc (expand_cfg_attrs): Fixed a bug where
            newly inserted cfg_attr attributes wheren't being reprocessed,
            and cleaned up the loop increment logic.
    
    Signed-off-by: lenny.chiadmi-delage <[email protected]>

Diff:
---
 gcc/rust/checks/errors/feature/rust-feature-gate.cc | 16 ++++++++++++++++
 gcc/rust/expand/rust-cfg-strip.cc                   | 10 ++++++----
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/gcc/rust/checks/errors/feature/rust-feature-gate.cc 
b/gcc/rust/checks/errors/feature/rust-feature-gate.cc
index 9df822b7e1c7..e5170b77808b 100644
--- a/gcc/rust/checks/errors/feature/rust-feature-gate.cc
+++ b/gcc/rust/checks/errors/feature/rust-feature-gate.cc
@@ -69,6 +69,22 @@ FeatureGate::visit (AST::Crate &crate)
                    valid_lib_features.emplace (name_str, item->get_locus ());
                }
            }
+         else if (type == AST::AttrInput::AttrInputType::META_ITEM)
+           {
+             const auto &meta_item
+               = static_cast<const AST::AttrInputMetaItemContainer &> (
+                 attr_input);
+             for (const auto &item : meta_item.get_items ())
+               {
+                 const auto &name_str = item->as_string ();
+
+                 // TODO: detect duplicates
+                 if (auto tname = Feature::as_name (name_str))
+                   valid_lang_features.insert (tname.value ());
+                 else
+                   valid_lib_features.emplace (name_str, item->get_locus ());
+               }
+           }
        }
     }
 
diff --git a/gcc/rust/expand/rust-cfg-strip.cc 
b/gcc/rust/expand/rust-cfg-strip.cc
index 3c5e74e7aae6..e8c6c3789421 100644
--- a/gcc/rust/expand/rust-cfg-strip.cc
+++ b/gcc/rust/expand/rust-cfg-strip.cc
@@ -124,6 +124,12 @@ expand_cfg_attrs (AST::AttrVec &attrs)
              attrs.insert (attrs.begin () + i,
                            std::make_move_iterator (new_attrs.begin ()),
                            std::make_move_iterator (new_attrs.end ()));
+
+             /* Decrement i so that the for loop's i++ will bring us back to
+              * position i, allowing us to reprocess the newly inserted
+              * attribute (in case it's also a cfg_attr that needs expansion)
+              */
+             i--;
            }
 
          /* do something - if feature (first token in tree) is in fact enabled,
@@ -133,10 +139,6 @@ expand_cfg_attrs (AST::AttrVec &attrs)
           * recursive, so check for expanded attributes being recursive and
           * possibly recursively call the expand_attrs? */
        }
-      else
-       {
-         i++;
-       }
     }
   attrs.shrink_to_fit ();
 }

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