diff options
author | Jason Merrill <jason@redhat.com> | 2021-04-03 01:07:36 -0400 |
---|---|---|
committer | Jason Merrill <jason@redhat.com> | 2022-05-13 13:39:31 -0400 |
commit | da999d938e516ff12b39a0aa7e8f6d97fbee60df (patch) | |
tree | fabd3f3d55b7b79ad9b9a12182d26f3e7d5867db | |
parent | 4231a43fd4ac6ccffd4d4b7cca70d45b2368cede (diff) |
c++: NRV in lambda in template [PR91217]
tsubst_lambda_expr was producing a function with two blocks that claimed to
be the outermost block in the function body, one from the call to
start_lambda_function in tsubst_lambda_expr, and one from tsubsting the
block added by start_lambda_function when we first parsed the lambda. This
messed with the named return value optimization, which only works for
variables in the outermost block.
gcc/cp/ChangeLog:
PR c++/91217
* pt.c (tsubst_lambda_expr): Skip the body block from
DECL_SAVED_TREE.
gcc/testsuite/ChangeLog:
PR c++/91217
* g++.dg/opt/nrv20.C: New test.
-rw-r--r-- | gcc/cp/pt.c | 9 | ||||
-rw-r--r-- | gcc/testsuite/g++.dg/opt/nrv20.C | 20 |
2 files changed, 27 insertions, 2 deletions
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index eeee23181fc..4bae467fa71 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -18472,8 +18472,13 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t complain, tree in_decl) the purposes of template argument deduction. */ complain = tf_warning_or_error; - tsubst_expr (DECL_SAVED_TREE (oldfn), args, complain, r, - /*constexpr*/false); + tree saved = DECL_SAVED_TREE (oldfn); + if (TREE_CODE (saved) == BIND_EXPR && BIND_EXPR_BODY_BLOCK (saved)) + /* We already have a body block from start_lambda_function, we don't + need another to confuse NRV (91217). */ + saved = BIND_EXPR_BODY (saved); + + tsubst_expr (saved, args, complain, r, /*constexpr*/false); finish_lambda_function (body); diff --git a/gcc/testsuite/g++.dg/opt/nrv20.C b/gcc/testsuite/g++.dg/opt/nrv20.C new file mode 100644 index 00000000000..ade0c28824a --- /dev/null +++ b/gcc/testsuite/g++.dg/opt/nrv20.C @@ -0,0 +1,20 @@ +// PR c++/91217 +// { dg-do compile { target c++11 } } +// { dg-additional-options -fdump-tree-gimple } +// { dg-final { scan-tree-dump-not "<retval> = a" "gimple" } } + +struct A +{ + int ar[42]; +}; + +template <class T> +A f() +{ + return [] { A a; return a; }(); +} + +int main() +{ + f<int>(); +} |