Issue #11393: Add the new faulthandler module

2 files changed, 256 insertions, 0 deletions

diff --git a/Python/pythonrun.c b/Python/pythonrun.c
index 38b2ab84fb..f787a4f8b3 100644
--- a/Python/pythonrun.c
+++ b/Python/pythonrun.c
@@ -70,6 +70,8 @@ extern void _PyUnicode_Init(void);
 extern void _PyUnicode_Fini(void);
 extern int _PyLong_Init(void);
 extern void PyLong_Fini(void);
+extern int _PyFaulthandler_Init(void);
+extern void _PyFaulthandler_Fini(void);
 
 #ifdef WITH_THREAD
 extern void _PyGILState_Init(PyInterpreterState *, PyThreadState *);
@@ -286,6 +288,10 @@ Py_InitializeEx(int install_sigs)
 
     _PyImportHooks_Init();
 
+    /* initialize the faulthandler module */
+    if (_PyFaulthandler_Init())
+        Py_FatalError("Py_Initialize: can't initialize faulthandler");
+
     /* Initialize _warnings. */
     _PyWarnings_Init();
 
@@ -454,6 +460,9 @@ Py_Finalize(void)
     /* Destroy the database used by _PyImport_{Fixup,Find}Extension */
     _PyImport_Fini();
 
+    /* unload faulthandler module */
+    _PyFaulthandler_Fini();
+
     /* Debugging stuff */
 #ifdef COUNT_ALLOCS
     dump_counts(stdout);
@@ -2100,11 +2109,23 @@ cleanup:
 void
 Py_FatalError(const char *msg)
 {
+    const int fd = fileno(stderr);
+    PyThreadState *tstate;
+
     fprintf(stderr, "Fatal Python error: %s\n", msg);
     fflush(stderr); /* it helps in Windows debug build */
     if (PyErr_Occurred()) {
         PyErr_PrintEx(0);
     }
+    else {
+        tstate = _Py_atomic_load_relaxed(&_PyThreadState_Current);
+        if (tstate != NULL) {
+            fputc('\n', stderr);
+            fflush(stderr);
+            _Py_DumpTraceback(fd, tstate);
+        }
+    }
+
 #ifdef MS_WINDOWS
     {
         size_t len = strlen(msg);
diff --git a/Python/traceback.c b/Python/traceback.c
index 59bb3f0d15..37673d93e0 100644
--- a/Python/traceback.c
+++ b/Python/traceback.c
@@ -13,6 +13,11 @@
 
 #define OFF(x) offsetof(PyTracebackObject, x)
 
+#define PUTS(fd, str) write(fd, str, strlen(str))
+#define MAX_STRING_LENGTH 100
+#define MAX_FRAME_DEPTH 100
+#define MAX_NTHREADS 100
+
 /* Method from Parser/tokenizer.c */
 extern char * PyTokenizer_FindEncoding(int);
 
@@ -402,3 +407,233 @@ PyTraceBack_Print(PyObject *v, PyObject *f)
         err = tb_printinternal((PyTracebackObject *)v, f, limit);
     return err;
 }
+
+/* Reverse a string. For example, "abcd" becomes "dcba".
+
+   This function is signal safe. */
+
+static void
+reverse_string(char *text, const size_t len)
+{
+    char tmp;
+    size_t i, j;
+    if (len == 0)
+        return;
+    for (i=0, j=len-1; i < j; i++, j--) {
+        tmp = text[i];
+        text[i] = text[j];
+        text[j] = tmp;
+    }
+}
+
+/* Format an integer in range [0; 999999] to decimal,
+   and write it into the file fd.
+
+   This function is signal safe. */
+
+static void
+dump_decimal(int fd, int value)
+{
+    char buffer[7];
+    int len;
+    if (value < 0 || 999999 < value)
+        return;
+    len = 0;
+    do {
+        buffer[len] = '0' + (value % 10);
+        value /= 10;
+        len++;
+    } while (value);
+    reverse_string(buffer, len);
+    write(fd, buffer, len);
+}
+
+/* Format an integer in range [0; 0xffffffff] to hexdecimal of 'width' digits,
+   and write it into the file fd.
+
+   This function is signal safe. */
+
+static void
+dump_hexadecimal(int width, unsigned long value, int fd)
+{
+    const char *hexdigits = "0123456789abcdef";
+    int len;
+    char buffer[sizeof(unsigned long) * 2 + 1];
+    len = 0;
+    do {
+        buffer[len] = hexdigits[value & 15];
+        value >>= 4;
+        len++;
+    } while (len < width || value);
+    reverse_string(buffer, len);
+    write(fd, buffer, len);
+}
+
+/* Write an unicode object into the file fd using ascii+backslashreplace.
+
+   This function is signal safe. */
+
+static void
+dump_ascii(int fd, PyObject *text)
+{
+    Py_ssize_t i, size;
+    int truncated;
+    Py_UNICODE *u;
+    char c;
+
+    size = PyUnicode_GET_SIZE(text);
+    u = PyUnicode_AS_UNICODE(text);
+
+    if (MAX_STRING_LENGTH < size) {
+        size = MAX_STRING_LENGTH;
+        truncated = 1;
+    }
+    else
+        truncated = 0;
+
+    for (i=0; i < size; i++, u++) {
+        if (*u < 128) {
+            c = (char)*u;
+            write(fd, &c, 1);
+        }
+        else if (*u < 256) {
+            PUTS(fd, "\\x");
+            dump_hexadecimal(2, *u, fd);
+        }
+        else
+#ifdef Py_UNICODE_WIDE
+        if (*u < 65536)
+#endif
+        {
+            PUTS(fd, "\\u");
+            dump_hexadecimal(4, *u, fd);
+#ifdef Py_UNICODE_WIDE
+        }
+        else {
+            PUTS(fd, "\\U");
+            dump_hexadecimal(8, *u, fd);
+#endif
+        }
+    }
+    if (truncated)
+        PUTS(fd, "...");
+}
+
+/* Write a frame into the file fd: "File "xxx", line xxx in xxx".
+
+   This function is signal safe. */
+
+static void
+dump_frame(int fd, PyFrameObject *frame)
+{
+    PyCodeObject *code;
+    int lineno;
+
+    code = frame->f_code;
+    PUTS(fd, "  File ");
+    if (code != NULL && code->co_filename != NULL
+        && PyUnicode_Check(code->co_filename))
+    {
+        write(fd, "\"", 1);
+        dump_ascii(fd, code->co_filename);
+        write(fd, "\"", 1);
+    } else {
+        PUTS(fd, "???");
+    }
+
+    /* PyFrame_GetLineNumber() was introduced in Python 2.7.0 and 3.2.0 */
+    lineno = PyCode_Addr2Line(frame->f_code, frame->f_lasti);
+    PUTS(fd, ", line ");
+    dump_decimal(fd, lineno);
+    PUTS(fd, " in ");
+
+    if (code != NULL && code->co_name != NULL
+        && PyUnicode_Check(code->co_name))
+        dump_ascii(fd, code->co_name);
+    else
+        PUTS(fd, "???");
+
+    write(fd, "\n", 1);
+}
+
+static int
+dump_traceback(int fd, PyThreadState *tstate, int write_header)
+{
+    PyFrameObject *frame;
+    unsigned int depth;
+
+    frame = _PyThreadState_GetFrame(tstate);
+    if (frame == NULL)
+        return -1;
+
+    if (write_header)
+        PUTS(fd, "Traceback (most recent call first):\n");
+    depth = 0;
+    while (frame != NULL) {
+        if (MAX_FRAME_DEPTH <= depth) {
+            PUTS(fd, "  ...\n");
+            break;
+        }
+        if (!PyFrame_Check(frame))
+            break;
+        dump_frame(fd, frame);
+        frame = frame->f_back;
+        depth++;
+    }
+    return 0;
+}
+
+int
+_Py_DumpTraceback(int fd, PyThreadState *tstate)
+{
+    return dump_traceback(fd, tstate, 1);
+}
+
+/* Write the thread identifier into the file 'fd': "Current thread 0xHHHH:\" if
+   is_current is true, "Thread 0xHHHH:\n" otherwise.
+
+   This function is signal safe. */
+
+static void
+write_thread_id(int fd, PyThreadState *tstate, int is_current)
+{
+    if (is_current)
+        PUTS(fd, "Current thread 0x");
+    else
+        PUTS(fd, "Thread 0x");
+    dump_hexadecimal(sizeof(long)*2, (unsigned long)tstate->thread_id, fd);
+    PUTS(fd, ":\n");
+}
+
+const char*
+_Py_DumpTracebackThreads(int fd, PyInterpreterState *interp,
+                         PyThreadState *current_thread)
+{
+    PyThreadState *tstate;
+    unsigned int nthreads;
+
+    /* Get the current interpreter from the current thread */
+    tstate = PyInterpreterState_ThreadHead(interp);
+    if (tstate == NULL)
+        return "unable to get the thread head state";
+
+    /* Dump the traceback of each thread */
+    tstate = PyInterpreterState_ThreadHead(interp);
+    nthreads = 0;
+    do
+    {
+        if (nthreads != 0)
+            write(fd, "\n", 1);
+        if (nthreads >= MAX_NTHREADS) {
+            PUTS(fd, "...\n");
+            break;
+        }
+        write_thread_id(fd, tstate, tstate == current_thread);
+        dump_traceback(fd, tstate, 0);
+        tstate = PyThreadState_Next(tstate);
+        nthreads++;
+    } while (tstate != NULL);
+
+    return NULL;
+}
+