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.
> 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
>>
