https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78985
--- Comment #8 from Martin Liška <marxin at gcc dot gnu.org> --- Merge base r235033 (of trunk and 6 branch) with following patch (that I installed couple weeks ago) works: diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c index cdc11fe..9e5e044 100644 --- a/gcc/cp/lambda.c +++ b/gcc/cp/lambda.c @@ -935,7 +935,7 @@ maybe_add_lambda_conv_op (tree type) { int ix = 0; tree src = DECL_CHAIN (DECL_ARGUMENTS (callop)); - tree tgt; + tree tgt = NULL; while (src) { There are just few commits for the file in between, let's see.