From 9cca177baec32a1ed1422a87a1f57cda2d2eb21a Mon Sep 17 00:00:00 2001 From: Dominique Quatravaux Date: Wed, 16 Feb 2022 09:15:39 -0500 Subject: [PATCH] gdb/darwin: remove not-so-harmless spurious call to `wait4` As seen in https://sourceware.org/bugzilla/show_bug.cgi?id=24069 this code will typically wait4() a second time on the same process that was already wait4()'d a few lines above. While this used to be harmless/idempotent (when we assumed that the process already exited), this now causes a deadlock in the WIFSTOPPED case. The early (~2019) history of bug #24069 cautiously suggests to use WNOHANG instead of outright deleting the call. However, tests on the current version of Darwin (Big Sur) demonstrate that gdb runs just fine without a redundant call to wait4(), as would be expected. Notwithstanding the debatable value of conserving bug compatibility with an OS release that is more than a decade old, there is scant evidence of what that double-wait4() was supposed to achieve in the first place - A cursory investigation with `git blame` pinpoints commits bb00b29d7802 and a80b95ba67e2 from the 2008-2009 era, but fails to answer the "why" question conclusively. Co-Authored-By: Philippe Blain Change-Id: Id4e4415d66d6ff6b3552b60d761693f17015e4a0 --- gdb/darwin-nat.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/gdb/darwin-nat.c b/gdb/darwin-nat.c index d96ce1a6c65..8b0ecfd5b77 100644 --- a/gdb/darwin-nat.c +++ b/gdb/darwin-nat.c @@ -1113,9 +1113,6 @@ darwin_nat_target::decode_message (mach_msg_header_t *hdr, inferior_debug (4, _("darwin_wait: pid=%d exit, status=0x%x\n"), res_pid, wstatus); - /* Looks necessary on Leopard and harmless... */ - wait4 (inf->pid, &wstatus, 0, NULL); - return ptid_t (inf->pid); } else -- 2.30.2