[gcc r16-6841] gccrs: util/attributes: error on malformed #[target_feature] input

[Arthur Cohen]

https://gcc.gnu.org/g:24357b9d970b12b4e3859a383472f3a238573b8c

commit r16-6841-g24357b9d970b12b4e3859a383472f3a238573b8c
Author: Jayant Chauhan <0001jayant@gmail.com>
Date:   Tue Jan 6 21:55:02 2026 +0530

    gccrs: util/attributes: error on malformed #[target_feature] input
    
    Emit a diagnostic when #[target_feature] is used without arguments,
    matching rustc behavior. This prevents silent acceptance of empty
    attributes and provides a helpful diagnostic that shows the expected form.
    
    Fixes Rust-GCC#4233
    
    gcc/rust/ChangeLog:
    
            * util/rust-attributes.cc (AttributeChecker::visit): Emit diagnostic.
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/target_feature-malformed-4233.rs: New test.
    
    Signed-off-by: Jayant Chauhan <0001jayant@gmail.com>

Diff:
---
 gcc/rust/util/rust-attributes.cc                            | 11 +++++++++++
 gcc/testsuite/rust/compile/target_feature-malformed-4233.rs |  6 ++++++
 2 files changed, 17 insertions(+)

diff --git a/gcc/rust/util/rust-attributes.cc b/gcc/rust/util/rust-attributes.cc
index c001ab52d860..ec14744fff49 100644
--- a/gcc/rust/util/rust-attributes.cc
+++ b/gcc/rust/util/rust-attributes.cc
@@ -864,6 +864,17 @@ AttributeChecker::visit (AST::Function &fun)
 	{
 	  check_crate_type (name, attribute);
 	}
+      else if (result.name == Attrs::TARGET_FEATURE)
+	{
+	  if (!attribute.has_attr_input ())
+	    {
+	      rust_error_at (attribute.get_locus (),
+			     "malformed %<target_feature%> attribute input");
+	      rust_inform (attribute.get_locus (),
+			   "must be of the form: %<#[target_feature(enable = "
+			   "\"name\")]%>");
+	    }
+	}
       else if (result.name == "no_mangle")
 	check_no_mangle_function (attribute, fun);
 
diff --git a/gcc/testsuite/rust/compile/target_feature-malformed-4233.rs b/gcc/testsuite/rust/compile/target_feature-malformed-4233.rs
new file mode 100644
index 000000000000..8e8c232e3d17
--- /dev/null
+++ b/gcc/testsuite/rust/compile/target_feature-malformed-4233.rs
@@ -0,0 +1,6 @@
+// { dg-options "-w" }
+// Test for issue #4233 - malformed #[target_feature] attribute input
+
+#[target_feature] // { dg-error "malformed .target_feature. attribute input" }
+unsafe fn foo_sse() {} 
+// { dg-note "must be of the form" "" { target *-*-* } .-2 }