Pick up Dominique Quatravaux 2cnd macOS modifications gdb

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  • Pick up Dominique Quatravaux 2cnd macOS modifications gdb
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Rustam Kovhaev via Gdb-patches July 9, 2021, 4:26 p.m.
From 92c389951e87ad12652d330b08f8d3a929c5ae5d Mon Sep 17 00:00:00 2001
From: Sam Warner <samuuel.r.warner@me.com>

Date: Thu, 8 Jul 2021 19:17:14 -0700
Subject: [PATCH] Pick up Dominique Quatravaux 2cnd macOS modifications gdb
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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.
 gdb/darwin-nat.c | 3 ---
 1 file changed, 3 deletions(-)



diff --git a/gdb/darwin-nat.c b/gdb/darwin-nat.c
index a6790792fb6..413e70811c4 100644
--- a/gdb/darwin-nat.c
+++ b/gdb/darwin-nat.c
@@ -1106,9 +1106,6 @@  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);