faulthandler: dump all threads by default

 * Set the default value of all_threads arguments to True
 * Py_FatalError() dumps all threads, instead of only the current thread

Dump only the current thread is not reliable. In some cases, Python is unable
to retrieve the state of the current thread and so is unable to dump the
traceback. faulthandler keeps a reference to the interpreter and so is always
able to dump the traceback of all threads.

1 files changed, 11 insertions, 10 deletions

diff --git a/Doc/library/faulthandler.rst b/Doc/library/faulthandler.rst
index c0b662502f..0c00f8f298 100644
--- a/Doc/library/faulthandler.rst
+++ b/Doc/library/faulthandler.rst
@@ -36,21 +36,22 @@ when Python is blocked (e.g. deadlock).
 Dump the traceback
 ------------------
 
-.. function:: dump_traceback(file=sys.stderr, all_threads=False)
+.. function:: dump_traceback(file=sys.stderr, all_threads=True)
 
-   Dump the traceback of the current thread, or of all threads if *all_threads*
-   is ``True``, into *file*.
+   Dump the traceback of all threads, or of the current thread if *all_threads*
+   is ``False``, into *file*.
 
 
 Fault handler state
 -------------------
 
-.. function:: enable(file=sys.stderr, all_threads=False)
+.. function:: enable(file=sys.stderr, all_threads=True)
 
    Enable the fault handler: install handlers for :const:`SIGSEGV`,
    :const:`SIGFPE`, :const:`SIGABRT`, :const:`SIGBUS` and :const:`SIGILL`
-   signals to dump the Python traceback. It dumps the traceback of the current
-   thread, or all threads if *all_threads* is ``True``, into *file*.
+   signals to dump the Python traceback. It dumps the traceback of the all
+   threads, or of the current thread if *all_threads* is ``False``, into
+   *file*.
 
 .. function:: disable()
 
@@ -86,11 +87,11 @@ Dump the tracebacks after a timeout
 Dump the traceback on a user signal
 -----------------------------------
 
-.. function:: register(signum, file=sys.stderr, all_threads=False)
+.. function:: register(signum, file=sys.stderr, all_threads=True)
 
    Register a user signal: install a handler for the *signum* signal to dump
-   the traceback of the current thread, or of all threads if *all_threads* is
-   ``True``, into *file*.
+   the traceback of all threads, or of the current thread if *all_threads* is
+   ``False``, into *file*.
 
    Not available on Windows.
 
@@ -123,7 +124,7 @@ Example of a segmentation fault on Linux: ::
     >>> ctypes.string_at(0)
     Fatal Python error: Segmentation fault
 
-    Traceback (most recent call first):
+    Current thread 0x00007fb899f39700:
       File "/home/python/cpython/Lib/ctypes/__init__.py", line 486 in string_at
       File "<stdin>", line 1 in <module>
     Segmentation fault