Hey Jon,
I think we should give debuggers a chance to announce themselves by
providing an entry point they can call (in the inferior) which sets a
flag. A set flag plus a tracer PID would then be a sufficient
indicator. The remaining code should also stay but some additional
code can be added:
On Sat, Jun 1, 2024 at 12:22 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> +_GLIBCXX_WEAK_DEFINITION
> +bool
> +std::is_debugger_present() noexcept
> +{
> +#if _GLIBCXX_HOSTED
> +# if _GLIBCXX_USE_PROC_SELF_STATUS
> + const string_view prefix = "TracerPid:\t";
> + ifstream in("/proc/self/status");
> + string line;
> + while (std::getline(in, line))
> + {
> + if (!line.starts_with(prefix))
> + continue;
> +
> + string_view tracer = line;
> + tracer.remove_prefix(prefix.size());
> + if (tracer.size() == 1 && tracer[0] == '0') [[likely]]
> + return false; // Not being traced.
> +
Here add something like:
if (debugger_announced)
return true;
> + in.close();
> + string_view cmd;
> + string proc_dir = "/proc/" + string(tracer) + '/';
> + in.open(proc_dir + "comm"); // since Linux 2.6.33
> + if (std::getline(in, line)) [[likely]]
> + cmd = line;
> + else
> + {
> + in.close();
> + in.open(proc_dir + "cmdline");
> + if (std::getline(in, line))
> + cmd = line.c_str(); // Only up to first '\0'
> + else
> + return false;
> + }
> +
> + for (auto i : {"gdb", "lldb"}) // known debuggers
> + if (cmd.ends_with(i))
> + return true;
> +
> + // We found the TracerPid line, no need to do any more work.
> + return false;
> + }
> +# endif
And then add
namespace {
bool debugger_announced = false;
}
auto debugger_attached()
{
debugger_announced = true;
return std::breakpoint;
}
I suggest to also return the breakpoint function to allow debuggers to
do something clever with it (e.g., set a breakpoint on the entry
instead of having to catch the fallout of the instruction that is
issued in the function (there might be a difference).
With the function any debugger not covered by the existing test can
make itself known.
