https://github.com/python/cpython/commit/646853df13492e2260befd5a13dba29af3c6be46 commit: 646853df13492e2260befd5a13dba29af3c6be46 branch: main author: Alex Malyshev <[email protected]> committer: vstinner <[email protected]> date: 2026-05-06T15:01:12Z summary:
gh-145559: Add PyUnstable_DumpTraceback() and PyUnstable_DumpTracebackThreads() (#148145) Co-authored-by: Petr Viktorin <[email protected]> Co-authored-by: Victor Stinner <[email protected]> files: A Misc/NEWS.d/next/C_API/2026-04-05-18-18-59.gh-issue-145559.qKJH9S.rst M Doc/c-api/exceptions.rst M Doc/whatsnew/3.15.rst M Include/cpython/traceback.h M Include/internal/pycore_traceback.h M Modules/faulthandler.c M Platforms/emscripten/node_entry.mjs M Platforms/emscripten/web_example_pyrepl_jspi/src.mjs M Python/pylifecycle.c M Python/traceback.c M configure M configure.ac diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst index 7a07818b7b4d1a..2f8f108ee27f6a 100644 --- a/Doc/c-api/exceptions.rst +++ b/Doc/c-api/exceptions.rst @@ -1348,3 +1348,67 @@ Tracebacks This function returns ``0`` on success, and returns ``-1`` with an exception set on failure. + +.. c:function:: const char* PyUnstable_DumpTraceback(int fd, PyThreadState *tstate) + + Write a trace of the Python stack in *tstate* into the file *fd*. The format + looks like:: + + Traceback (most recent call first): + File "xxx", line xxx in <xxx> + File "xxx", line xxx in <xxx> + ... + File "xxx", line xxx in <xxx> + + This function is meant to debug situations such as segfaults, fatal errors, + and similar. The file and function names it outputs are encoded to ASCII with + backslashreplace and truncated to 500 characters. It writes only the first + 100 frames; further frames are truncated with the line ``...``. + + This function will return ``NULL`` on success, or an error message on error. + + This function is intended for use in crash scenarios such as signal handlers + for SIGSEGV, where the interpreter may be in an inconsistent state. Given + that it reads interpreter data structures that may be partially modified, the + function might produce incomplete output or it may even crash itself. + + The caller does not need to hold an :term:`attached thread state`, nor does + *tstate* need to be attached. + + .. versionadded:: next + +.. c:function:: const char* PyUnstable_DumpTracebackThreads(int fd, PyInterpreterState *interp, PyThreadState *current_tstate, Py_ssize_t max_threads) + + Write the traces of all Python threads in *interp* into the file *fd*. + + If *interp* is ``NULL`` then this function will try to identify the current + interpreter using thread-specific storage. If it cannot, it will return an + error. + + If *current_tstate* is not ``NULL`` then it will be used to identify what the + current thread is in the written output. If it is ``NULL`` then this function + will identify the current thread using thread-specific storage. It is not an + error if the function is unable to get the current Python thread state. + + This function will return ``NULL`` on success, or an error message on error. + + This function is meant to debug debug situations such as segfaults, fatal + errors, and similar. It calls :c:func:`PyUnstable_DumpTraceback` for each + thread. It only writes the tracebacks of the first *max_threads* threads, + further output is truncated with the line ``...``. If *max_threads* is 0, the + function will use a default value of 100 for the argument. + + This function is intended for use in crash scenarios such as signal handlers + for SIGSEGV, where the interpreter may be in an inconsistent state. Given + that it reads interpreter data structures that may be partially modified, the + function might produce incomplete output or it may even crash itself. + + The caller does not need to hold an :term:`attached thread state`, nor does + *current_tstate* need to be attached. + + .. warning:: + On the :term:`free-threaded build`, this function is not thread-safe. If + another thread deletes its :term:`thread state` while this function is being + called, the process will likely crash. + + .. versionadded:: next diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst index 2ca28378e6ef73..f3bcdd5f1a35b9 100644 --- a/Doc/whatsnew/3.15.rst +++ b/Doc/whatsnew/3.15.rst @@ -2352,6 +2352,11 @@ New features Python 3.14. (Contributed by Victor Stinner in :gh:`142417`.) +* Add :c:func:`PyUnstable_DumpTraceback` and + :c:func:`PyUnstable_DumpTracebackThreads` functions to output Python + stacktraces. + (Contributed by Alex Malyshev in :gh:`145559`.) + Changed C APIs -------------- diff --git a/Include/cpython/traceback.h b/Include/cpython/traceback.h index 81c51944f136f2..7f42730f1b0919 100644 --- a/Include/cpython/traceback.h +++ b/Include/cpython/traceback.h @@ -11,3 +11,11 @@ struct _traceback { int tb_lasti; int tb_lineno; }; + +PyAPI_FUNC(const char*) PyUnstable_DumpTraceback(int fd, PyThreadState *tstate); + +PyAPI_FUNC(const char*) PyUnstable_DumpTracebackThreads( + int fd, + PyInterpreterState *interp, + PyThreadState *current_tstate, + Py_ssize_t max_threads); diff --git a/Include/internal/pycore_traceback.h b/Include/internal/pycore_traceback.h index fbf6bc2c41f51d..e016afaa5c5687 100644 --- a/Include/internal/pycore_traceback.h +++ b/Include/internal/pycore_traceback.h @@ -14,56 +14,6 @@ PyAPI_FUNC(int) _Py_DisplaySourceLine(PyObject *, PyObject *, int, int, int *, P // Export for 'pyexact' shared extension PyAPI_FUNC(void) _PyTraceback_Add(const char *, const char *, int); -/* Write the Python traceback into the file 'fd'. For example: - - Traceback (most recent call first): - File "xxx", line xxx in <xxx> - File "xxx", line xxx in <xxx> - ... - File "xxx", line xxx in <xxx> - - This function is written for debug purpose only, to dump the traceback in - the worst case: after a segmentation fault, at fatal error, etc. That's why, - it is very limited. Strings are truncated to 100 characters and encoded to - ASCII with backslashreplace. It doesn't write the source code, only the - function name, filename and line number of each frame. Write only the first - 100 frames: if the traceback is truncated, write the line " ...". - - This function is signal safe. */ - -extern void _Py_DumpTraceback( - int fd, - PyThreadState *tstate); - -/* Write the traceback of all threads into the file 'fd'. current_thread can be - NULL. - - Return NULL on success, or an error message on error. - - This function is written for debug purpose only. It calls - _Py_DumpTraceback() for each thread, and so has the same limitations. It - only write the traceback of the first 100 threads: write "..." if there are - more threads. - - If current_tstate is NULL, the function tries to get the Python thread state - of the current thread. It is not an error if the function is unable to get - the current Python thread state. - - If interp is NULL, the function tries to get the interpreter state from - the current Python thread state, or from - _PyGILState_GetInterpreterStateUnsafe() in last resort. - - It is better to pass NULL to interp and current_tstate, the function tries - different options to retrieve this information. - - This function is signal safe. */ - -extern const char* _Py_DumpTracebackThreads( - int fd, - PyInterpreterState *interp, - PyThreadState *current_tstate, - Py_ssize_t max_threads); - /* Write a Unicode object into the file descriptor fd. Encode the string to ASCII using the backslashreplace error handler. diff --git a/Misc/NEWS.d/next/C_API/2026-04-05-18-18-59.gh-issue-145559.qKJH9S.rst b/Misc/NEWS.d/next/C_API/2026-04-05-18-18-59.gh-issue-145559.qKJH9S.rst new file mode 100644 index 00000000000000..9495d42160a9cd --- /dev/null +++ b/Misc/NEWS.d/next/C_API/2026-04-05-18-18-59.gh-issue-145559.qKJH9S.rst @@ -0,0 +1,3 @@ +Rename ``_Py_DumpTraceback`` and ``_Py_DumpTracebackThreads`` to +:c:func:`PyUnstable_DumpTraceback` and +:c:func:`PyUnstable_DumpTracebackThreads`. diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c index 923f6f5b56d32b..1b4f0c2302daae 100644 --- a/Modules/faulthandler.c +++ b/Modules/faulthandler.c @@ -7,7 +7,7 @@ #include "pycore_runtime.h" // _Py_ID() #include "pycore_signal.h" // Py_NSIG #include "pycore_time.h" // _PyTime_FromSecondsObject() -#include "pycore_traceback.h" // _Py_DumpTracebackThreads +#include "pycore_traceback.h" // _Py_DumpStack() #ifdef HAVE_UNISTD_H # include <unistd.h> // _exit() #endif @@ -206,14 +206,15 @@ faulthandler_dump_traceback(int fd, int all_threads, PyThreadState *tstate = PyGILState_GetThisThreadState(); if (all_threads == 1) { - (void)_Py_DumpTracebackThreads(fd, NULL, tstate, max_threads); + (void)PyUnstable_DumpTracebackThreads(fd, NULL, tstate, max_threads); } else { if (all_threads == FT_IGNORE_ALL_THREADS) { PUTS(fd, "<Cannot show all threads while the GIL is disabled>\n"); } - if (tstate != NULL) - _Py_DumpTraceback(fd, tstate); + if (tstate != NULL) { + PyUnstable_DumpTraceback(fd, tstate); + } } reentrant = 0; @@ -277,17 +278,18 @@ faulthandler_dump_traceback_py_impl(PyObject *module, PyObject *file, /* gh-128400: Accessing other thread states while they're running * isn't safe if those threads are running. */ _PyEval_StopTheWorld(interp); - errmsg = _Py_DumpTracebackThreads(fd, NULL, tstate, max_threads); + errmsg = PyUnstable_DumpTracebackThreads(fd, NULL, tstate, max_threads); _PyEval_StartTheWorld(interp); - if (errmsg != NULL) { - PyErr_SetString(PyExc_RuntimeError, errmsg); - Py_XDECREF(file); - return NULL; - } } else { - _Py_DumpTraceback(fd, tstate); + errmsg = PyUnstable_DumpTraceback(fd, tstate); } + if (errmsg != NULL) { + PyErr_SetString(PyExc_RuntimeError, errmsg); + Py_XDECREF(file); + return NULL; + } + Py_XDECREF(file); if (PyErr_CheckSignals()) @@ -713,8 +715,8 @@ faulthandler_thread(void *unused) (void)_Py_write_noraise(thread.fd, thread.header, (int)thread.header_len); - errmsg = _Py_DumpTracebackThreads(thread.fd, thread.interp, NULL, - thread.max_threads); + errmsg = PyUnstable_DumpTracebackThreads(thread.fd, thread.interp, NULL, + thread.max_threads); ok = (errmsg == NULL); if (thread.exit) diff --git a/Platforms/emscripten/node_entry.mjs b/Platforms/emscripten/node_entry.mjs index 9478b7714adbc8..110aadc5de1014 100644 --- a/Platforms/emscripten/node_entry.mjs +++ b/Platforms/emscripten/node_entry.mjs @@ -57,6 +57,6 @@ try { // Show JavaScript exception and traceback console.warn(e); // Show Python exception and traceback - Module.__Py_DumpTraceback(2, Module._PyGILState_GetThisThreadState()); + Module.PyUnstable_DumpTraceback(2, Module._PyGILState_GetThisThreadState()); process.exit(1); } diff --git a/Platforms/emscripten/web_example_pyrepl_jspi/src.mjs b/Platforms/emscripten/web_example_pyrepl_jspi/src.mjs index 5642372c9d2472..38a622117c2a50 100644 --- a/Platforms/emscripten/web_example_pyrepl_jspi/src.mjs +++ b/Platforms/emscripten/web_example_pyrepl_jspi/src.mjs @@ -189,6 +189,6 @@ try { // Show JavaScript exception and traceback console.warn(e); // Show Python exception and traceback - Module.__Py_DumpTraceback(2, Module._PyGILState_GetThisThreadState()); + Module.PyUnstable_DumpTraceback(2, Module._PyGILState_GetThisThreadState()); process.exit(1); } diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c index 728c0acdd4df67..8f31756f3df840 100644 --- a/Python/pylifecycle.c +++ b/Python/pylifecycle.c @@ -29,7 +29,7 @@ #include "pycore_setobject.h" // _PySet_NextEntry() #include "pycore_stats.h" // _PyStats_InterpInit() #include "pycore_sysmodule.h" // _PySys_ClearAttrString() -#include "pycore_traceback.h" // _Py_DumpTracebackThreads() +#include "pycore_traceback.h" // PyUnstable_TracebackThreads() #include "pycore_tuple.h" // _PyTuple_FromPair #include "pycore_typeobject.h" // _PyTypes_InitTypes() #include "pycore_typevarobject.h" // _Py_clear_generic_types() @@ -3348,9 +3348,9 @@ _Py_FatalError_DumpTracebacks(int fd, PyInterpreterState *interp, /* display the current Python stack */ #ifndef Py_GIL_DISABLED - _Py_DumpTracebackThreads(fd, interp, tstate, 0); + PyUnstable_DumpTracebackThreads(fd, interp, tstate, 0); #else - _Py_DumpTraceback(fd, tstate); + PyUnstable_DumpTraceback(fd, tstate); #endif } diff --git a/Python/traceback.c b/Python/traceback.c index f0e0df7101bc21..50a79d78d2e10e 100644 --- a/Python/traceback.c +++ b/Python/traceback.c @@ -1167,10 +1167,11 @@ dump_traceback(int fd, PyThreadState *tstate, int write_header) The caller is responsible to call PyErr_CheckSignals() to call Python signal handlers if signals were received. */ -void -_Py_DumpTraceback(int fd, PyThreadState *tstate) +const char* +PyUnstable_DumpTraceback(int fd, PyThreadState *tstate) { dump_traceback(fd, tstate, 1); + return NULL; } #if defined(HAVE_PTHREAD_GETNAME_NP) || defined(HAVE_PTHREAD_GET_NAME_NP) @@ -1264,16 +1265,16 @@ write_thread_id(int fd, PyThreadState *tstate, int is_current) The caller is responsible to call PyErr_CheckSignals() to call Python signal handlers if signals were received. */ const char* _Py_NO_SANITIZE_THREAD -_Py_DumpTracebackThreads(int fd, PyInterpreterState *interp, - PyThreadState *current_tstate, - Py_ssize_t max_threads) +PyUnstable_DumpTracebackThreads(int fd, PyInterpreterState *interp, + PyThreadState *current_tstate, + Py_ssize_t max_threads) { if (max_threads == 0) { max_threads = DEFAULT_MAX_NTHREADS; } if (current_tstate == NULL) { - /* _Py_DumpTracebackThreads() is called from signal handlers by + /* PyUnstable_DumpTracebackThreads() is called from signal handlers by faulthandler. SIGSEGV, SIGFPE, SIGABRT, SIGBUS and SIGILL are synchronous signals diff --git a/configure b/configure index 627f5ee4888a1f..d4a0a9d74b7631 100755 --- a/configure +++ b/configure @@ -9788,7 +9788,7 @@ fi as_fn_append LINKFORSHARED " -sFORCE_FILESYSTEM -lidbfs.js -lnodefs.js -lproxyfs.js -lworkerfs.js" as_fn_append LINKFORSHARED " -sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV,HEAPU32,TTY,ERRNO_CODES" - as_fn_append LINKFORSHARED " -sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,_PyGILState_GetThisThreadState,__Py_DumpTraceback,__PyEM_EMSCRIPTEN_TRAMPOLINE_OFFSET" + as_fn_append LINKFORSHARED " -sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,_PyGILState_GetThisThreadState,__PyEM_EMSCRIPTEN_TRAMPOLINE_OFFSET" as_fn_append LINKFORSHARED " -sSTACK_SIZE=5MB" as_fn_append LINKFORSHARED " -sTEXTDECODER=2" diff --git a/configure.ac b/configure.ac index 4f968b25d91566..395bfc30651171 100644 --- a/configure.ac +++ b/configure.ac @@ -2406,7 +2406,7 @@ AS_CASE([$ac_sys_system], dnl Include file system support AS_VAR_APPEND([LINKFORSHARED], [" -sFORCE_FILESYSTEM -lidbfs.js -lnodefs.js -lproxyfs.js -lworkerfs.js"]) AS_VAR_APPEND([LINKFORSHARED], [" -sEXPORTED_RUNTIME_METHODS=FS,callMain,ENV,HEAPU32,TTY,ERRNO_CODES"]) - AS_VAR_APPEND([LINKFORSHARED], [" -sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,_PyGILState_GetThisThreadState,__Py_DumpTraceback,__PyEM_EMSCRIPTEN_TRAMPOLINE_OFFSET"]) + AS_VAR_APPEND([LINKFORSHARED], [" -sEXPORTED_FUNCTIONS=_main,_Py_Version,__PyRuntime,_PyGILState_GetThisThreadState,__PyEM_EMSCRIPTEN_TRAMPOLINE_OFFSET"]) AS_VAR_APPEND([LINKFORSHARED], [" -sSTACK_SIZE=5MB"]) dnl Avoid bugs in JS fallback string decoding path AS_VAR_APPEND([LINKFORSHARED], [" -sTEXTDECODER=2"]) _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
