[gcc r17-3090] gccrs: Emit function-scope drops for unit tail expressions

https://gcc.gnu.org/g:8b20ce82d7c7113d5ca8c6d198c8ed674f4b51d4

commit r17-3090-g8b20ce82d7c7113d5ca8c6d198c8ed674f4b51d4
Author: Lishin <[email protected]>
Date:   Fri Jun 19 18:14:41 2026 +0000

    gccrs: Emit function-scope drops for unit tail expressions
    
    Add the missing drop calls before returning from unit tail expressions.
    
    gcc/rust/ChangeLog:
    
            * backend/rust-compile-base.cc
            (HIRCompileBase::compile_function_body): Emit current scope drops
            for unit tail expressions.
    
    gcc/testsuite/ChangeLog:
    
            * rust/execute/drop-function-scope-unit-tail.rs: New test.
    
    Signed-off-by: Lishin <[email protected]>

Diff:
---
 gcc/rust/backend/rust-compile-base.cc              |  2 +
 .../rust/execute/drop-function-scope-unit-tail.rs  | 46 ++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/gcc/rust/backend/rust-compile-base.cc b/gcc/rust/backend/rust-compile-base.cc
index e049e18a4604..4e618243b3b3 100644
--- a/gcc/rust/backend/rust-compile-base.cc
+++ b/gcc/rust/backend/rust-compile-base.cc
@@ -739,6 +739,8 @@ HIRCompileBase::compile_function_body (tree fndecl,
 	  // just add the stmt expression
 	  ctx->add_statement (return_value);
 
+	  CompileDrop::emit_current_scope_drop_calls (ctx);
+
 	  // now just return unit expression
 	  tree unit_expr = unit_expression (locus);
 	  tree return_stmt
diff --git a/gcc/testsuite/rust/execute/drop-function-scope-unit-tail.rs b/gcc/testsuite/rust/execute/drop-function-scope-unit-tail.rs
new file mode 100644
index 000000000000..ab5bf3fb3e19
--- /dev/null
+++ b/gcc/testsuite/rust/execute/drop-function-scope-unit-tail.rs
@@ -0,0 +1,46 @@
+// { dg-output "d\r*\nd\r*\n" }
+// { dg-additional-options "-w" }
+#![feature(no_core)]
+#![feature(lang_items)]
+#![no_core]
+
+extern "C" {
+    fn printf(s: *const i8, ...);
+}
+
+#[lang = "sized"]
+pub trait Sized {}
+
+#[lang = "drop"]
+pub trait Drop {
+    fn drop(&mut self);
+}
+
+struct Droppable;
+
+impl Drop for Droppable {
+    fn drop(&mut self) {
+        let msg = "d\n\0" as *const str as *const i8;
+        unsafe {
+            printf(msg);
+        }
+    }
+}
+
+fn foo() {}
+
+fn unit_tail_call() {
+    let _x = Droppable;
+    foo()
+}
+
+fn unit_tail_literal() {
+    let _x = Droppable;
+    ()
+}
+
+fn main() -> i32 {
+    unit_tail_call();
+    unit_tail_literal();
+    0
+}
\ No newline at end of file