On Fri, 11 Apr 2025 at 09:12, Jonathan Wakely <jwak...@redhat.com> wrote:
>
> On Fri, 11 Apr 2025 at 08:00, Tomasz Kaminski <tkami...@redhat.com> wrote:
> >
> >
> >
> > On Thu, Apr 10, 2025 at 6:53 PM Jonathan Wakely <jwak...@redhat.com> wrote:
> >>
> >> 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.
> >>
> >> 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.
> >> * 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.
> >> ---
> >>
> >> I sent v1 of this patch in June last year:
> >> https://gcc.gnu.org/pipermail/gcc-patches/2024-June/653293.html
> >> My comments about testing with GDB still apply.
> >>
> >> Compared to v1, this adds a void __gnu_cxx::attach_debugger(bool)
> >> function that could be called by debuggers to announce that they are
> >> attaching and detaching. It also adds a systemtap probe point to
> >> std::breakpoint().
> >>
> >> Tested x86_64-linux.
> >>
> >> N.B. this only adds new symbols to the libstdc++exp.a archive, not to
> >> libstdc++.so so it's not a risky change at this stage.
> >>
> >> libstdc++-v3/config.h.in | 9 +
> >> libstdc++-v3/configure | 22 +++
> >> libstdc++-v3/configure.ac | 9 +
> >> libstdc++-v3/include/Makefile.am | 1 +
> >> libstdc++-v3/include/Makefile.in | 1 +
> >> libstdc++-v3/include/bits/version.def | 8 +
> >> libstdc++-v3/include/bits/version.h | 10 ++
> >> libstdc++-v3/include/std/debugging | 77 ++++++++
> >> libstdc++-v3/src/c++26/Makefile.am | 4 +-
> >> libstdc++-v3/src/c++26/Makefile.in | 7 +-
> >> libstdc++-v3/src/c++26/debugging.cc | 165 ++++++++++++++++++
> >> .../19_diagnostics/debugging/breakpoint.cc | 13 ++
> >> .../debugging/breakpoint_if_debugging.cc | 13 ++
> >> .../debugging/is_debugger_present.cc | 14 ++
> >> 14 files changed, 350 insertions(+), 3 deletions(-)
> >> create mode 100644 libstdc++-v3/include/std/debugging
> >> create mode 100644 libstdc++-v3/src/c++26/debugging.cc
> >> create mode 100644
> >> libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint.cc
> >> create mode 100644
> >> libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc
> >> create mode 100644
> >> libstdc++-v3/testsuite/19_diagnostics/debugging/is_debugger_present.cc
> >>
> >> diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
> >> index 77bbaf1beaa..3f1331ff36f 100644
> >> --- a/libstdc++-v3/config.h.in
> >> +++ b/libstdc++-v3/config.h.in
> >> @@ -70,6 +70,9 @@
> >> /* Define to 1 if you have the `cosl' function. */
> >> #undef HAVE_COSL
> >>
> >> +/* Define to 1 if you have the <debugapi.h> header file. */
> >> +#undef HAVE_DEBUGAPI_H
> >> +
> >> /* Define to 1 if you have the declaration of `strnlen', and to 0 if you
> >> don't. */
> >> #undef HAVE_DECL_STRNLEN
> >> @@ -439,6 +442,9 @@
> >> /* Define to 1 if you have the <sys/param.h> header file. */
> >> #undef HAVE_SYS_PARAM_H
> >>
> >> +/* Define to 1 if you have the <sys/ptrace.h> header file. */
> >> +#undef HAVE_SYS_PTRACE_H
> >> +
> >> /* Define to 1 if you have the <sys/resource.h> header file. */
> >> #undef HAVE_SYS_RESOURCE_H
> >>
> >> @@ -850,6 +856,9 @@
> >> /* Define if nl_langinfo_l should be used for std::text_encoding. */
> >> #undef _GLIBCXX_USE_NL_LANGINFO_L
> >>
> >> +/* Define if /proc/self/status should be used for <debugging>. */
> >> +#undef _GLIBCXX_USE_PROC_SELF_STATUS
> >> +
> >> /* Define if pthreads_num_processors_np is available in <pthread.h>. */
> >> #undef _GLIBCXX_USE_PTHREADS_NUM_PROCESSORS_NP
> >>
> >> diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
> >> index 819a1d82876..8143df91c38 100755
> >> --- a/libstdc++-v3/configure
> >> +++ b/libstdc++-v3/configure
> >> @@ -54700,6 +54700,28 @@ ac_compiler_gnu=$ac_cv_c_compiler_gnu
> >>
> >>
> >>
> >> +# For std::is_debugger_present
> >> +case "$target_os" in
> >> + linux*)
> >> +
> >> +$as_echo "#define _GLIBCXX_USE_PROC_SELF_STATUS 1" >>confdefs.h
> >> +
> >> + ;;
> >> +esac
> >> +for ac_header in sys/ptrace.h debugapi.h
> >> +do :
> >> + as_ac_Header=`$as_echo "ac_cv_header_$ac_header" | $as_tr_sh`
> >> +ac_fn_c_check_header_mongrel "$LINENO" "$ac_header" "$as_ac_Header"
> >> "$ac_includes_default"
> >> +if eval test \"x\$"$as_ac_Header"\" = x"yes"; then :
> >> + cat >>confdefs.h <<_ACEOF
> >> +#define `$as_echo "HAVE_$ac_header" | $as_tr_cpp` 1
> >> +_ACEOF
> >> +
> >> +fi
> >> +
> >> +done
> >> +
> >> +
> >> # Define documentation rules conditionally.
> >>
> >> # See if makeinfo has been installed and is modern enough
> >> diff --git a/libstdc++-v3/configure.ac b/libstdc++-v3/configure.ac
> >> index a6c01b29e94..83adb46454e 100644
> >> --- a/libstdc++-v3/configure.ac
> >> +++ b/libstdc++-v3/configure.ac
> >> @@ -587,6 +587,15 @@ GLIBCXX_CHECK_FILEBUF_NATIVE_HANDLES
> >> # For std::text_encoding
> >> GLIBCXX_CHECK_TEXT_ENCODING
> >>
> >> +# For std::is_debugger_present
> >> +case "$target_os" in
> >> + linux*)
> >> + AC_DEFINE([_GLIBCXX_USE_PROC_SELF_STATUS],1,
> >> + [Define if /proc/self/status should be used for
> >> <debugging>.])
> >> + ;;
> >> +esac
> >> +AC_CHECK_HEADERS([sys/ptrace.h debugapi.h])
> >> +
> >> # Define documentation rules conditionally.
> >>
> >> # See if makeinfo has been installed and is modern enough
> >> diff --git a/libstdc++-v3/include/Makefile.am
> >> b/libstdc++-v3/include/Makefile.am
> >> index 537774c2668..6bb3f3dc3d6 100644
> >> --- a/libstdc++-v3/include/Makefile.am
> >> +++ b/libstdc++-v3/include/Makefile.am
> >> @@ -67,6 +67,7 @@ std_headers = \
> >> ${std_srcdir}/codecvt \
> >> ${std_srcdir}/complex \
> >> ${std_srcdir}/condition_variable \
> >> + ${std_srcdir}/debugging \
> >> ${std_srcdir}/deque \
> >> ${std_srcdir}/execution \
> >> ${std_srcdir}/filesystem \
> >> diff --git a/libstdc++-v3/include/Makefile.in
> >> b/libstdc++-v3/include/Makefile.in
> >> index 7b96b2207f8..81c3cfce4c4 100644
> >> --- a/libstdc++-v3/include/Makefile.in
> >> +++ b/libstdc++-v3/include/Makefile.in
> >> @@ -423,6 +423,7 @@ std_freestanding = \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/codecvt \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/complex \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/condition_variable \
> >> +@GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/debugging \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/deque \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/execution \
> >> @GLIBCXX_HOSTED_TRUE@ ${std_srcdir}/filesystem \
> >> diff --git a/libstdc++-v3/include/bits/version.def
> >> b/libstdc++-v3/include/bits/version.def
> >> index 2ec1b40bd38..092d0427e4a 100644
> >> --- a/libstdc++-v3/include/bits/version.def
> >> +++ b/libstdc++-v3/include/bits/version.def
> >> @@ -1841,6 +1841,14 @@ ftms = {
> >> };
> >> };
> >>
> >> +ftms = {
> >> + name = debugging;
> >> + values = {
> >> + v = 202403;
> >> + cxxmin = 26;
> >> + };
> >>
> >> +};
> >> +
> >> ftms = {
> >> name = fstream_native_handle;
> >> values = {
> >> diff --git a/libstdc++-v3/include/bits/version.h
> >> b/libstdc++-v3/include/bits/version.h
> >> index 04c1349c84b..12892fc135d 100644
> >> --- a/libstdc++-v3/include/bits/version.h
> >> +++ b/libstdc++-v3/include/bits/version.h
> >> @@ -2044,6 +2044,16 @@
> >> #endif /* !defined(__cpp_lib_constexpr_new) &&
> >> defined(__glibcxx_want_constexpr_new) */
> >> #undef __glibcxx_want_constexpr_new
> >>
> >> +#if !defined(__cpp_lib_debugging)
> >> +# if (__cplusplus > 202302L)
> >> +# define __glibcxx_debugging 202403L
> >> +# if defined(__glibcxx_want_all) || defined(__glibcxx_want_debugging)
> >> +# define __cpp_lib_debugging 202403L
> >> +# endif
> >> +# endif
> >> +#endif /* !defined(__cpp_lib_debugging) &&
> >> defined(__glibcxx_want_debugging) */
> >> +#undef __glibcxx_want_debugging
> >> +
> >> #if !defined(__cpp_lib_fstream_native_handle)
> >> # if (__cplusplus > 202302L) && _GLIBCXX_HOSTED
> >> # define __glibcxx_fstream_native_handle 202306L
> >> diff --git a/libstdc++-v3/include/std/debugging
> >> b/libstdc++-v3/include/std/debugging
> >> new file mode 100644
> >> index 00000000000..4cf7e4acbc4
> >> --- /dev/null
> >> +++ b/libstdc++-v3/include/std/debugging
> >> @@ -0,0 +1,77 @@
> >> +// Debugging support -*- C++ -*-
> >> +
> >> +// Copyright The GNU Toolchain Authors.
> >> +//
> >> +// This file is part of the GNU ISO C++ Library. This library is free
> >> +// software; you can redistribute it and/or modify it under the
> >> +// terms of the GNU General Public License as published by the
> >> +// Free Software Foundation; either version 3.
> >> +
> >> +// This library is distributed in the hope that it will be useful,
> >> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> >> +// GNU General Public License for more details.
> >> +
> >> +// Under Section 7 of GPL version 3, you are granted additional
> >> +// permissions described in the GCC Runtime Library Exception, version
> >> +// 3.1, as published by the Free Software Foundation.
> >> +
> >> +// You should have received a copy of the GNU General Public License and
> >> +// a copy of the GCC Runtime Library Exception along with this program;
> >> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> >> +// <http://www.gnu.org/licenses/>.
> >> +
> >> +/** @file include/debugging
> >> + * This is a Standard C++ Library header.
> >> + */
> >> +
> >> +#ifndef _GLIBCXX_DEBUGGING
> >> +#define _GLIBCXX_DEBUGGING 1
> >> +
> >> +#define __glibcxx_want_debugging
> >> +#include <bits/version.h>
> >> +
> >> +#if __cpp_lib_debugging // C++ >= 26
> >> +namespace std _GLIBCXX_VISIBILITY(default)
> >> +{
> >> +// N.B. _GLIBCXX_BEGIN_NAMESPACE_VERSION is not used here.
> >> +
> >> +/** Try to determine if the program is running under control of a
> >> debugger.
> >> + *
> >> + * On GNU/Linux systems this function will only return true if the program
> >> + * is being traced by another program which is known to be a debugger.
> >> + * This is determined by checking the command name of the tracing program
> >> + * against a list of known debuggers, such as "gdb".
> >> + *
> >> + * On other POSIX-based systems, this function will return true if the
> >> + * program is being traced by any other process, which means it can return
> >> + * true for non-debugger utilities that use the ptrace system call.
> >> + *
> >> + * @since C++26
> >> + */
> >> +bool
> >> +is_debugger_present() noexcept;
> >> +
> >> +/** Stop the program with a breakpoint or debug trap.
> >> + *
> >> + * The details of how a breakpoint is implemented are platform-specific.
> >> + * Some systems provide a special instruction, such as `int3` in x86.
> >> + * When no more appropriate mechanism is available, this will stop the
> >> + * program using `__builtin_trap()`. It might not be possible for the
> >> + * program to continue after such a breakpoint.
> >> + *
> >> + * @since C++26
> >> + */
> >> +void
> >> +breakpoint() noexcept;
> >> +
> >> +/** Stop the program if it is running under control of a debugger.
> >> + *
> >> + * @since C++26
> >> + */
> >> +void
> >> +breakpoint_if_debugging() noexcept;
> >> +
> >> +} // namespace std
> >> +#endif
> >> +#endif // _GLIBCXX_DEBUGGING
> >> diff --git a/libstdc++-v3/src/c++26/Makefile.am
> >> b/libstdc++-v3/src/c++26/Makefile.am
> >> index 5defa4ac481..4123b7dd369 100644
> >> --- a/libstdc++-v3/src/c++26/Makefile.am
> >> +++ b/libstdc++-v3/src/c++26/Makefile.am
> >> @@ -35,7 +35,9 @@ else
> >> inst_sources =
> >> endif
> >>
> >> -sources = text_encoding.cc
> >> +sources = \
> >> + debugging.cc \
> >> + text_encoding.cc
> >>
> >> vpath % $(top_srcdir)/src/c++26
> >>
> >> diff --git a/libstdc++-v3/src/c++26/Makefile.in
> >> b/libstdc++-v3/src/c++26/Makefile.in
> >> index 77e73b2b265..1c317d6ac7c 100644
> >> --- a/libstdc++-v3/src/c++26/Makefile.in
> >> +++ b/libstdc++-v3/src/c++26/Makefile.in
> >> @@ -121,7 +121,7 @@ CONFIG_CLEAN_FILES =
> >> CONFIG_CLEAN_VPATH_FILES =
> >> LTLIBRARIES = $(noinst_LTLIBRARIES)
> >> libc__26convenience_la_LIBADD =
> >> -am__objects_1 = text_encoding.lo
> >> +am__objects_1 = debugging.lo text_encoding.lo
> >> am__objects_2 =
> >> @GLIBCXX_HOSTED_TRUE@am_libc__26convenience_la_OBJECTS = \
> >> @GLIBCXX_HOSTED_TRUE@ $(am__objects_1) $(am__objects_2)
> >> @@ -430,7 +430,10 @@ headers =
> >>
> >> # XTEMPLATE_FLAGS = -fno-implicit-templates
> >> @ENABLE_EXTERN_TEMPLATE_TRUE@inst_sources =
> >> -sources = text_encoding.cc
> >> +sources = \
> >> + debugging.cc \
> >> + text_encoding.cc
> >> +
> >> @GLIBCXX_HOSTED_FALSE@libc__26convenience_la_SOURCES =
> >> @GLIBCXX_HOSTED_TRUE@libc__26convenience_la_SOURCES = $(sources)
> >> $(inst_sources)
> >>
> >> diff --git a/libstdc++-v3/src/c++26/debugging.cc
> >> b/libstdc++-v3/src/c++26/debugging.cc
> >> new file mode 100644
> >> index 00000000000..5ad85309ba1
> >> --- /dev/null
> >> +++ b/libstdc++-v3/src/c++26/debugging.cc
> >> @@ -0,0 +1,165 @@
> >> +// Implementation of <debugging> -*- C++ -*-
> >> +
> >> +// Copyright The GNU Toolchain Authors.
> >> +//
> >> +// This file is part of the GNU ISO C++ Library. This library is free
> >> +// software; you can redistribute it and/or modify it under the
> >> +// terms of the GNU General Public License as published by the
> >> +// Free Software Foundation; either version 3.
> >> +
> >> +// This library is distributed in the hope that it will be useful,
> >> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
> >> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> >> +// GNU General Public License for more details.
> >> +
> >> +// Under Section 7 of GPL version 3, you are granted additional
> >> +// permissions described in the GCC Runtime Library Exception, version
> >> +// 3.1, as published by the Free Software Foundation.
> >> +
> >> +// You should have received a copy of the GNU General Public License and
> >> +// a copy of the GCC Runtime Library Exception along with this program;
> >> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
> >> +// <http://www.gnu.org/licenses/>.
> >> +
> >> +#include <debugging>
> >> +
> >> +#if __cpp_lib_debugging
> >> +
> >> +#if _GLIBCXX_USE_PROC_SELF_STATUS
> >> +# include <fstream>
> >> +# include <string>
> >> +#endif
> >> +
> >> +#if _GLIBCXX_HAVE_SYS_PTRACE_H
> >> +# include <sys/ptrace.h>
> >> +# include <errno.h>
> >> +#endif
> >> +
> >> +#if _GLIBCXX_HAVE_DEBUGAPI_H
> >> +# include <debugapi.h>
> >> +#endif
> >> +
> >> +#ifdef _GLIBCXX_HAVE_SYS_SDT_H
> >> +# include <sys/sdt.h>
> >> +/* We only want to use stap probes starting with v3. Earlier versions
> >> + added too much startup cost. */
> >> +# if defined (STAP_PROBE) && _SDT_NOTE_TYPE >= 3
> >> +# define PROBE(name) STAP_PROBE(libstdcxx, name)
> >> +# endif
> >> +#endif
> >> +
> >> +#ifndef PROBE
> >> +# define PROBE(name)
> >> +#endif
> >> +
> >> +namespace
> >> +{
> >> + volatile bool debugger_attached = false;
> >> +}
> >> +
> >> +namespace __gnu_cxx
> >> +{
> >> + // This should be called by debuggers when they attach and detach.
> >> + void attach_debugger(bool attached) { debugger_attached = attached; }
> >> +}
> >> +
> >> +_GLIBCXX_WEAK_DEFINITION
> >> +bool
> >> +std::is_debugger_present() noexcept
> >> +{
> >> + if (debugger_attached)
> >> + return true;
> >> +
> >> +#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.
> >> +
> >> + 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
> >> +# if _GLIBCXX_HAVE_SYS_PTRACE_H
> >
> > Are _GLIBCXX_USE_PROC_SELF_STATUS and _GLIBCXX_HAVE_SYS_PTRACE_H
> > exclusive, i.e. both cannot be true at same time?
>
> They're not exclusive, e.g. Linux has both /proc/self and ptrace. Most
> UNIX systems only have ptrace.
N.B. Solaris does have /proc/self/status, but it's a binary file
containing a struct pstatus (see 'man -s 5 proc' on Solaris) which
doesn't give us the info we need.
That's why configure.ac currently only defines USE_PROC_SELF_STATUS for Linux.
>
> > If not, using `ptrace` seems to be preferablable, given that it does not
> > involve fstreams.
>
> But it can give false positives. There are other uses of ptrace that
> are not debuggers, e.g. running the program under strace. The
> /proc/self version checks for the tracer name, so should only detect
> real debuggers.
>
> >>
> >> + if (::ptrace(PTRACE_TRACEME, 0, 1, 0) == -1)
> >> + return errno == EPERM;
> >> +# endif
> >> +# if _GLIBCXX_HAVE_DEBUGAPI_H && defined(_WIN32) && !defined(__CYGWIN__)
> >> + return IsDebuggerPresent();
> >> +# endif
> >> +#endif // HOSTED
> >> + return false;
> >> +}
> >> +
> >> +void
> >> +std::breakpoint() noexcept
> >> +{
> >> + PROBE(std::breakpoint);
> >> +
> >> +#if _GLIBCXX_HAVE_DEBUGAPI_H && defined(_WIN32) && !defined(__CYGWIN__)
> >> + DebugBreak();
> >> +#elif __has_builtin(__builtin_debugtrap)
> >> + __builtin_debugtrap(); // Clang
> >> +#elif defined(__i386__) || defined(__x86_64__)
> >> + __asm__ volatile ("int3; nop");
> >> +#elifdef __thumb__
> >> + __asm__ volatile (".inst 0xde01");
> >> +#elifdef __aarch64__
> >> + __asm__ volatile (".inst 0xd4200000");
> >> +#elifdef __arm__
> >> + __asm__ volatile (".inst 0xe7f001f0");
> >> +#elifdef __riscv
> >> + /* section 2.8 in the RISC-V unprivileged ISA manual says for
> >> semi-hosted
> >> + * environments we want the sequence:
> >> + * slli x0, x0, 0x1f # Entry NOP
> >> + * ebreak # Break to debugger
> >> + * srai x0, x0, 7 # NOP encoding the semihosting call number 7
> >> + */
> >> + __asm__ volatile (".4byte 0x00100073");
> >> +#elifdef __powerpc__
> >> + __asm__ volatile(".4byte 0x7d821008");
> >> +#else
> >> + __builtin_trap();
> >> +#endif
> >> +} // If the debugger stops here, std::breakpoint() was called.
> >> +
> >> +// This is intentionally not defined inline. A non-inline definition
> >> allows
> >> +// debuggers to insert a breakpoint on calls to the function, avoiding the
> >> +// overhead of calling `is_debugger_present()`.
> >> +void
> >> +std::breakpoint_if_debugging() noexcept
> >> +{
> >> + if (std::is_debugger_present()) [[unlikely]]
> >> + std::breakpoint();
> >> +}
> >> +
> >> +#endif // __cpp_lib_debugging
> >> diff --git a/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint.cc
> >> b/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint.cc
> >> new file mode 100644
> >> index 00000000000..ad24177f644
> >> --- /dev/null
> >> +++ b/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint.cc
> >> @@ -0,0 +1,13 @@
> >> +// { dg-do run { target c++26 xfail c++26 } }
> >> +// { dg-options "-lstdc++exp" }
> >> +// { dg-require-cpp-feature-test __cpp_lib_debugging }
> >> +#include <debugging>
> >> +#include <type_traits>
> >> +
> >> +static_assert( noexcept(std::breakpoint()) );
> >> +static_assert( std::is_void_v<decltype(std::breakpoint())> );
> >> +
> >> +int main()
> >> +{
> >> + std::breakpoint();
> >> +}
> >> diff --git
> >> a/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc
> >>
> >> b/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc
> >> new file mode 100644
> >> index 00000000000..26461836ef7
> >> --- /dev/null
> >> +++
> >> b/libstdc++-v3/testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc
> >> @@ -0,0 +1,13 @@
> >> +// { dg-do run { target c++26 } }
> >> +// { dg-options "-lstdc++exp" }
> >> +// { dg-require-cpp-feature-test __cpp_lib_debugging }
> >> +#include <debugging>
> >> +#include <type_traits>
> >> +
> >> +static_assert( noexcept(std::breakpoint_if_debugging()) );
> >> +static_assert( std::is_void_v<decltype(std::breakpoint_if_debugging())> );
> >> +
> >> +int main()
> >> +{
> >> + std::breakpoint_if_debugging();
> >> +}
> >> diff --git
> >> a/libstdc++-v3/testsuite/19_diagnostics/debugging/is_debugger_present.cc
> >> b/libstdc++-v3/testsuite/19_diagnostics/debugging/is_debugger_present.cc
> >> new file mode 100644
> >> index 00000000000..8dbfa694243
> >> --- /dev/null
> >> +++
> >> b/libstdc++-v3/testsuite/19_diagnostics/debugging/is_debugger_present.cc
> >> @@ -0,0 +1,14 @@
> >> +// { dg-do run { target c++26 } }
> >> +// { dg-options "-lstdc++exp" }
> >> +// { dg-require-cpp-feature-test __cpp_lib_debugging }
> >> +#include <debugging>
> >> +#include <type_traits>
> >> +#include <testsuite_hooks.h>
> >> +
> >> +static_assert( noexcept(std::is_debugger_present()) );
> >> +static_assert( std::is_same_v<decltype(std::is_debugger_present()), bool>
> >> );
> >> +
> >> +int main()
> >> +{
> >> + VERIFY( ! std::is_debugger_present() );
> >> +}
> >> --
> >> 2.49.0
> >>
