Export _Py_DumpTraceback and _Py_DumpTracebackThreads as PyUnstable_ functions

These functions stopped being exported in #107215.  However, they are the only
way to print a Python stacktrace safely from a signal handler, making them very
useful for extensions.  Re-export them as PyUnstable functions.

Author: alexmalyshev

Include/internal/pycore_traceback.h

@@ -14,55 +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);
-
 /* Write a Unicode object into the file descriptor fd. Encode the string to
    ASCII using the backslashreplace error handler.
 

Include/traceback.h

@@ -13,6 +13,50 @@ PyAPI_FUNC(int) PyTraceBack_Print(PyObject *, PyObject *);
 PyAPI_DATA(PyTypeObject) PyTraceBack_Type;
 #define PyTraceBack_Check(v) Py_IS_TYPE((v), &PyTraceBack_Type)
 
+/* 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. */
+PyAPI_FUNC(void) PyUnstable_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
+   PyUnstable_DumpTraceback() for each thread, and so has the same limitations. It
+   only writes 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. */
+PyAPI_FUNC(const char*) PyUnstable_DumpTracebackThreads(
+    int fd,
+    PyInterpreterState *interp,
+    PyThreadState *current_tstate);
 
 #ifndef Py_LIMITED_API
 #  define Py_CPYTHON_TRACEBACK_H

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
@@ -205,14 +205,15 @@ faulthandler_dump_traceback(int fd, int all_threads,
     PyThreadState *tstate = PyGILState_GetThisThreadState();
 
     if (all_threads == 1) {
-        (void)_Py_DumpTracebackThreads(fd, NULL, tstate);
+        (void)PyUnstable_DumpTracebackThreads(fd, NULL, tstate);
     }
     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;
@@ -273,7 +274,7 @@ 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);
+        errmsg = PyUnstable_DumpTracebackThreads(fd, NULL, tstate);
         _PyEval_StartTheWorld(interp);
         if (errmsg != NULL) {
             PyErr_SetString(PyExc_RuntimeError, errmsg);
@@ -282,7 +283,7 @@ faulthandler_dump_traceback_py_impl(PyObject *module, PyObject *file,
         }
     }
     else {
-        _Py_DumpTraceback(fd, tstate);
+        PyUnstable_DumpTraceback(fd, tstate);
     }
     Py_XDECREF(file);
 
@@ -703,7 +704,7 @@ faulthandler_thread(void *unused)
 
         (void)_Py_write_noraise(thread.fd, thread.header, (int)thread.header_len);
 
-        errmsg = _Py_DumpTracebackThreads(thread.fd, thread.interp, NULL);
+        errmsg = PyUnstable_DumpTracebackThreads(thread.fd, thread.interp, NULL);
         ok = (errmsg == NULL);
 
         if (thread.exit)

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"     // _Py_DumpTraceback_Init()
 #include "pycore_typeobject.h"    // _PyTypes_InitTypes()
 #include "pycore_typevarobject.h" // _Py_clear_generic_types()
 #include "pycore_unicodeobject.h" // _PyUnicode_InitTypes()
@@ -3208,9 +3208,9 @@ _Py_FatalError_DumpTracebacks(int fd, PyInterpreterState *interp,
 
     /* display the current Python stack */
 #ifndef Py_GIL_DISABLED
-    _Py_DumpTracebackThreads(fd, interp, tstate);
+    PyUnstable_DumpTracebackThreads(fd, interp, tstate);
 #else
-    _Py_DumpTraceback(fd, tstate);
+    PyUnstable_DumpTraceback(fd, tstate);
 #endif
 }
 

Python/traceback.c

@@ -1168,7 +1168,7 @@ 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)
+PyUnstable_DumpTraceback(int fd, PyThreadState *tstate)
 {
     dump_traceback(fd, tstate, 1);
 }
@@ -1264,11 +1264,11 @@ 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)
+PyUnstable_DumpTracebackThreads(int fd, PyInterpreterState *interp,
+                                PyThreadState *current_tstate)
 {
     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

Tools/wasm/emscripten/node_entry.mjs

@@ -53,6 +53,6 @@ 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);
 }

Tools/wasm/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);
 }

configure

@@ -2357,7 +2357,7 @@ 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"])
-    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"])