[gcc r12-6333] c++: destroy retval on throwing cleanup in try [PR33799]

[gcc r12-6333] c++: destroy retval on throwing cleanup in try [PR33799]

[Jason Merrill]

https://gcc.gnu.org/g:b10e031458d541f794dfaa08ba606487603a4bb6

commit r12-6333-gb10e031458d541f794dfaa08ba606487603a4bb6
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jan 5 17:01:12 2022 -0500

    c++: destroy retval on throwing cleanup in try [PR33799]
    
    My earlier attempt to fix this bug didn't handle the case where both the
    return and the throwing cleanup are within a try-block that catches and
    discards the exception.  Fixed by adding the retval cleanup to any
    try-blocks as well as the function body.  PR102191 pointed out that we also
    weren't handling templates properly, so I moved the call out of the parser.
    
            PR c++/33799
            PR c++/102191
    
    gcc/cp/ChangeLog:
    
            * except.c (maybe_splice_retval_cleanup): Check
            current_binding_level.
            * semantics.c (do_poplevel): Call it here.
            * parser.c (cp_parser_compound_statement): Not here.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/eh/return1.C: Add temporary in try block case.
            * g++.dg/cpp2a/constexpr-dtor11.C: New test.

Diff:
---
 gcc/cp/except.c                               | 29 +++++++++-----
 gcc/cp/parser.c                               |  3 --
 gcc/cp/semantics.c                            |  2 +
 gcc/testsuite/g++.dg/cpp2a/constexpr-dtor11.C | 12 ++++++
 gcc/testsuite/g++.dg/eh/return1.C             | 56 ++++++++++++++++++++++++---
 5 files changed, 84 insertions(+), 18 deletions(-)

diff --git a/gcc/cp/except.c b/gcc/cp/except.c
index 5c7eeff9035..bcd9f84431b 100644
--- a/gcc/cp/except.c
+++ b/gcc/cp/except.c
@@ -1294,26 +1294,35 @@ maybe_set_retval_sentinel ()
 		 current_retval_sentinel, boolean_true_node);
 }
 
-/* COMPOUND_STMT is the STATEMENT_LIST for the current function body.  If
-   current_retval_sentinel was set in this function, wrap the body in a
-   CLEANUP_STMT to destroy the return value on throw.  */
+/* COMPOUND_STMT is the STATEMENT_LIST for some block.  If COMPOUND_STMT is the
+   current function body or a try block, and current_retval_sentinel was set in
+   this function, wrap the block in a CLEANUP_STMT to destroy the return value
+   on throw.  */
 
 void
 maybe_splice_retval_cleanup (tree compound_stmt)
 {
-  /* If need_retval_cleanup set current_retval_sentinel, wrap the function body
-     in a CLEANUP_STMT to handle destroying the return value.  */
-  if (!DECL_CONSTRUCTOR_P (current_function_decl)
+  /* If we need a cleanup for the return value, add it in at the same level as
+     pushdecl_outermost_localscope.  And also in try blocks.  */
+  bool function_body
+    = (current_binding_level->level_chain
+       && current_binding_level->level_chain->kind == sk_function_parms);
+
+  if ((function_body || current_binding_level->kind == sk_try)
+      && !DECL_CONSTRUCTOR_P (current_function_decl)
       && !DECL_DESTRUCTOR_P (current_function_decl)
       && current_retval_sentinel)
     {
       location_t loc = DECL_SOURCE_LOCATION (current_function_decl);
-
-      /* Add a DECL_EXPR for current_retval_sentinel.  */
       tree_stmt_iterator iter = tsi_start (compound_stmt);
       tree retval = DECL_RESULT (current_function_decl);
-      tree decl_expr = build_stmt (loc, DECL_EXPR, current_retval_sentinel);
-      tsi_link_before (&iter, decl_expr, TSI_SAME_STMT);
+
+      if (function_body)
+	{
+	  /* Add a DECL_EXPR for current_retval_sentinel.  */
+	  tree decl_expr = build_stmt (loc, DECL_EXPR, current_retval_sentinel);
+	  tsi_link_before (&iter, decl_expr, TSI_SAME_STMT);
+	}
 
       /* Skip past other decls, they can't contain a return.  */
       while (TREE_CODE (tsi_stmt (iter)) == DECL_EXPR)
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 6b91a0ce491..f40e707d47c 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -12751,9 +12751,6 @@ cp_parser_compound_statement (cp_parser *parser, tree in_statement_expr,
   /* Parse an (optional) statement-seq.  */
   cp_parser_statement_seq_opt (parser, in_statement_expr);
 
-  if (function_body)
-    maybe_splice_retval_cleanup (compound_stmt);
-
   /* Consume the `}'.  */
   braces.require_close (parser);
 
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 58f45e9c3e3..645654768e3 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -624,6 +624,8 @@ do_poplevel (tree stmt_list)
 {
   tree block = NULL;
 
+  maybe_splice_retval_cleanup (stmt_list);
+
   if (stmts_are_full_exprs_p ())
     block = poplevel (kept_level_p (), 1, 0);
 
diff --git a/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor11.C b/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor11.C
new file mode 100644
index 00000000000..e371f89a10e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constexpr-dtor11.C
@@ -0,0 +1,12 @@
+// PR c++/102191
+// { dg-do compile { target c++20 } }
+
+struct X {
+  struct A {
+    constexpr ~A() noexcept(false) { }
+  };
+
+  constexpr A operator()(auto...) { return {}; }
+};
+
+void f() { []() consteval { X{}(); }(); }
diff --git a/gcc/testsuite/g++.dg/eh/return1.C b/gcc/testsuite/g++.dg/eh/return1.C
index 5ef2f1dee85..ac2225405da 100644
--- a/gcc/testsuite/g++.dg/eh/return1.C
+++ b/gcc/testsuite/g++.dg/eh/return1.C
@@ -11,13 +11,16 @@ int c, d;
 #define THROWS
 #endif
 
+extern "C" int printf (const char *, ...);
+#define DEBUG // printf ("%p %s\n", this, __PRETTY_FUNCTION__)
+
 struct X
 {
-  X(bool throws) : throws_(throws) { ++c; }
-  X(const X& x) : throws_(x.throws_) { ++c; }
+  X(bool throws) : throws_(throws) { ++c; DEBUG; }
+  X(const X& x); // not defined
   ~X() THROWS
   {
-    ++d;
+    ++d; DEBUG;
     if (throws_) { throw 1; }
   }
 private:
@@ -42,6 +45,40 @@ void h()
 #endif
 }
 
+X i()
+{
+  try {
+    X x(true);
+    return X(false);
+  } catch(...) {}
+  return X(false);
+}
+
+X j()
+{
+  try {
+    return X(true),X(false);
+  } catch(...) {}
+  return X(false);
+}
+
+template <class T>
+T k()
+{
+  try {
+    return T(true),T(false);
+  } catch (...) {}
+  return T(true),T(false);
+}
+
+X l() try { return X(true),X(false); }
+  catch (...) { return X(true),X(false); }
+
+template <class T>
+T m()
+  try { return T(true),T(false); }
+  catch (...) { return T(true),T(false); }
+
 int main()
 {
   try { f(); }
@@ -53,6 +90,15 @@ int main()
   try { h(); }
   catch (...) {}
 
-  if (c != d)
-    throw;
+  try { i(); }
+  catch (...) {}
+
+  try { j(); } catch (...) {}
+
+  try { k<X>(); } catch (...) {}
+
+  try { l(); } catch (...) {}
+  try { m<X>(); } catch (...) {}
+
+  return c - d;
 }