On Thu, May 1, 2025 at 12:59 PM Jonathan Wakely <jwak...@redhat.com> wrote:
>
> This includes the P2810R4 (is_debugger_present is_replaceable) changes,
> allowing std::is_debugger_present to be replaced by the program.
>
> It would be good to provide a macOS definition of is_debugger_present as
> per https://developer.apple.com/library/archive/qa/qa1361/_index.html
> but that isn't included in this change.
>
> The src/c++26/debugging.cc file defines a global volatile int which can
> be set by debuggers to indicate when they are attached and detached from
> a running process. This allows std::is_debugger_present() to give a
> reliable answer, and additionally allows a debugger to choose how
> std::breakpoint() should behave. Setting the global to a positive value
> will cause std::breakpoint() to use that value as an argument to
> std::raise, so debuggers that prefer SIGABRT for breakpoints can select
> that. By default std::breakpoint() will use a platform-specific action
> such as the INT3 instruction on x86, or GCC's __builtin_trap().
>
> On Linux the std::is_debugger_present() function checks whether the
> process is being traced by a process named "gdb", "gdbserver" or
> "lldb-server", to try to avoid interpreting other tracing processes
> (such as strace) as a debugger. There have been comments suggesting this
> isn't desirable and that std::is_debugger_present() should just return
> true for any tracing process (which is the case for non-Linux targets
> that support the ptrace system call).
>
> libstdc++-v3/ChangeLog:
>
> * config.h.in: Regenerate.
> * configure: Regenerate.
> * configure.ac: Check for facilities needed by <debugging>.
> * include/Makefile.am: Add new header.
> * include/Makefile.in: Regenerate.
> * include/bits/version.def (debugging): Add.
> * include/bits/version.h: Regenerate.
> * include/precompiled/stdc++.h: Add new header.
> * src/c++26/Makefile.am: Add new file.
> * src/c++26/Makefile.in: Regenerate.
> * include/std/debugging: New file.
> * src/c++26/debugging.cc: New file.
> * testsuite/19_diagnostics/debugging/breakpoint.cc: New test.
> * testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc:
> New test.
> * testsuite/19_diagnostics/debugging/is_debugger_present.cc: New
> test.
> * testsuite/19_diagnostics/debugging/is_debugger_present-2.cc:
> New test.
> ---
> +#elif defined(__i386__) || defined(__x86_64__)
> + __asm__ volatile ("int3; nop");
Just a small nit - can this be written as:
"int3\n\tnop"
And perhaps add a small comment about "nop", that is added due to gdb issues.
Thanks,
Uros.
