From: Pedro Alves <pedro@palves.net>
Date: Fri, 2 Jun 2023 22:40:23 +0000 (+0100)
Subject: gdb/Cygwin: Fix attach pid error message
X-Git-Tag: gdb-15-branchpoint~217
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=43ca4ec2996a6bfbb8726f1c753aeb85fe0f92a4;p=thirdparty%2Fbinutils-gdb.git

gdb/Cygwin: Fix attach pid error message

On Cygwin, with "attach PID":

 - GDB first tries to interpret PID as a Windows native PID, and tries
   to attach to that.

 - if the attach fails, GDB then tries to interpret the PID as a
   Cygwin PID, and attach to that.

If converting the user-provided PID from a Cygwin PID to a Windows PID
fails, you get this:

 (gdb) attach 12345
 Can't attach to process 0 (error 2: The system cannot find the file specified.)

Note "process 0".

With the fix in this commit, we'll now get:

 (gdb) attach 12345
 Can't attach to process 12345 (error 2: The system cannot find the file specified.)

I noticed this while looking at gdb.log after running
gdb.base/attach.exp on Cygwin.

Change-Id: I05b9dc1f3a634a822ea49bb5c61719f5e62c8514
Approved-By: Luis Machado <luis.machado@arm.com>
---

diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 3b3239ab938..70f955d9797 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -2048,11 +2048,20 @@ windows_nat_target::attach (const char *args, int from_tty)
 #ifdef __CYGWIN__
       if (!ok)
 	{
-	  /* Try fall back to Cygwin pid.  */
-	  pid = cygwin_internal (CW_CYGWIN_PID_TO_WINPID, pid);
+	  /* Maybe PID was a Cygwin PID.  Try the corresponding native
+	     Windows PID.  */
+	  DWORD winpid = cygwin_internal (CW_CYGWIN_PID_TO_WINPID, pid);
 
-	  if (pid > 0)
-	    ok = DebugActiveProcess (pid);
+	  if (winpid != 0)
+	    {
+	      /* It was indeed a Cygwin PID.  Fully switch to the
+		 Windows PID from here on.  We don't do this
+		 unconditionally to avoid ending up with PID=0 in the
+		 error message below.  */
+	      pid = winpid;
+
+	      ok = DebugActiveProcess (winpid);
+	    }
 	}
 #endif