Place the tracing of return values after any generated 'out:' label, as it is important to see even the errors caused by calling a function in the wrong handle state. Fixes: 9df088bfa9 --- Multiple bugs found today, but only time to submit one patch so far. I found them all while trying to implement .list_exports in nbdkit. Bug 1: 'nbdinfo --list --json $uri' produces invalid JSON if there are 0 or more than 1 exports. We need to move the '"exports":[' and ']' into list_all_exports(), not list_one_export(), and manage correct trailing comma output. (We only tested nbdinfo with qemu-nbd, which only lists one export, explaining how we missed this) Bug 2: nbd_get_nr_list_exports() fails if the handle is still in READY state, even though there were exports listed and available in that case. I see no reason to forbid this during READY; but I've also mentioned that there are probably more changes coming to the way we do list export handling in libnbd to allow the reuse of a single handle rather than our current hacks of one handle per export. (We only tested nbdinfo with qemu-nbd, which generally does NOT allow NBD_OPT_GO on the '' export if it was advertising some other export; nbdkit is more forgiving, explaining why I hit a case where nbdinfo was calling this function in the wrong state) Bug 3: this patch. When a function fails due to use in the wrong state, the debug output was useless in telling me why. generator/C.ml | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/generator/C.ml b/generator/C.ml index 4a0b45d..2c62d4e 100644 --- a/generator/C.ml +++ b/generator/C.ml @@ -542,13 +542,13 @@ let generate_lib_api_c () = pr " ret = nbd_unlocked_%s " name; print_arg_list ~wrap:true ~types:false ~handle:true args optargs; pr ";\n"; - if may_set_error then ( - pr "\n"; - print_trace_leave ret; - pr "\n" - ); + pr "\n"; if !need_out_label then pr " out:\n"; + if may_set_error then ( + print_trace_leave ret; + pr "\n" + ); if is_locked then ( pr " if (h->public_state != get_next_state (h))\n"; pr " h->public_state = get_next_state (h);\n";