* Pavel Labath:
> On 04/01/2019 17:38, Florian Weimer via lldb-dev wrote:
>> Consider this example program:
>>
>> #include <err.h>
>> #include <sys/wait.h>
>> #include <unistd.h>
>>
>> #include <lldb/API/SBDebugger.h>
>> #include <lldb/API/SBProcess.h>
>> #include <lldb/API/SBTarget.h>
>>
>> int
>> main(void)
>> {
>> // Target process for the debugger.
>> pid_t pid = fork();
>> if (pid < 0)
>> err(1, "fork");
>> if (pid == 0)
>> while (true)
>> pause();
>>
>> lldb::SBDebugger::Initialize();
>> {
>> auto debugger(lldb::SBDebugger::Create());
>> if (!debugger.IsValid())
>> errx(1, "SBDebugger::Create failed");
>>
>> auto target(debugger.CreateTarget(nullptr));
>> if (!target.IsValid())
>> errx(1, "SBDebugger::CreateTarget failed");
>>
>> lldb::SBAttachInfo attachinfo(pid);
>> lldb::SBError error;
>> auto process(target.Attach(attachinfo, error));
>> if (!process.IsValid())
>> errx(1, "SBTarget::Attach failed: %s", error.GetCString());
>> error = process.Detach();
>> if (error.Fail())
>> errx(1, "SBProcess::Detach failed: %s", error.GetCString());
>> }
>> lldb::SBDebugger::Terminate();
>>
>> if (kill(pid, SIGKILL) != 0)
>> err(1, "kill");
>> if (waitpid(pid, NULL, 0) < 0)
>> err(1, "waitpid");
>>
>> return 0;
>> }
>>
>> Run it in a loop like this:
>>
>> $ while ./test-attach ; do date; done
>>
>> On Linux x86-64 (Fedora 29), with LLDB 7 (lldb-7.0.0-1.fc29.x86_64) and
>> kernel 4.19.12 (kernel-4.19.12-301.fc29.x86_64), after 100 iterations or
>> so, attaching to the newly created process fails:
>>
>> test-attach: SBTarget::Attach failed: lost connection
>>
>> This also reproduces occasionally with LLDB itself (with “lldb -p PID”).
>>
>> Any suggestions how to get more information about the cause of this
>> error?
>>
>
> I would recommend enabling gdb-remote logging (so something like:
> debugger.HandleCommand("log enable gdb-remote packets")) to see at
> which stage do we actually lose the gdb-server connection.
Thanks. I enabled logging like this:
auto debugger(lldb::SBDebugger::Create());
if (!debugger.IsValid())
errx(1, "SBDebugger::Create failed");
debugger.HandleCommand("log enable gdb-remote packets");
auto target(debugger.CreateTarget(nullptr));
if (!target.IsValid())
errx(1, "SBDebugger::CreateTarget failed");
And here's the output I get:
test-attach < 1> send packet: +
test-attach history[1] tid=0x1cab < 1> send packet: +
test-attach < 19> send packet: $QStartNoAckMode#b0
test-attach < 1> read packet: +
test-attach < 6> read packet: $OK#9a
test-attach < 1> send packet: +
test-attach < 41> send packet: $qSupported:xmlRegisters=i386,arm,mips#12
test-attach < 124> read packet:
$PacketSize=20000;QStartNoAckMode+;QThreadSuffixSupported+;QListThreadsInStopReply+;qEcho+;QPassSignals+;qXfer:auxv:read+#be
test-attach < 26> send packet: $QThreadSuffixSupported#e4
test-attach < 6> read packet: $OK#9a
test-attach < 27> send packet: $QListThreadsInStopReply#21
test-attach < 6> read packet: $OK#9a
test-attach < 13> send packet: $qHostInfo#9b
test-attach < 11> send packet: $qEcho:1#5b
test-attach: SBTarget::Attach failed: lost connection
Florian
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