From 786ea6bc23c26a0ec98d5cbc80633615f9fa8cb1 Mon Sep 17 00:00:00 2001
From: Skip Montanaro <skip@pobox.com>
Date: Mon, 1 Mar 2004 15:44:05 +0000
Subject: [PATCH] Add pystack definition to Misc/gdbinit with some explanation
 of its behavior and add flag comments to ceval.c and main.c alerting people
 to the coupling between pystack and the layout of those files.

---
 Misc/gdbinit   | 23 +++++++++++++++++++++++
 Modules/main.c |  3 +++
 Python/ceval.c |  4 ++++
 3 files changed, 30 insertions(+)

diff --git a/Misc/gdbinit b/Misc/gdbinit
index 05f6a9151c5..4790adae54c 100644
--- a/Misc/gdbinit
+++ b/Misc/gdbinit
@@ -34,3 +34,26 @@ x/s ((PyStringObject*)f->f_code->co_filename)->ob_sval
 x/s ((PyStringObject*)f->f_code->co_name)->ob_sval
 p f->f_lineno
 end
+
+# Here's a somewhat fragile way to print the entire Python stack from gdb.
+# It's fragile because the tests for the value of $pc depend on the layout
+# of specific functions in the C source code.
+
+# Explanation of while and if tests: We want to pop up the stack until we
+# land in Py_Main (this is probably an incorrect assumption in an embedded
+# interpreter, but the test can be extended by an interested party).  If
+# Py_Main <= $pc <= Py_GetArgcArv is true $pc is in Py_Main(), so the while
+# tests succeeds as long as it's not true.  In a similar fashion the if
+# statement tests to see if we are in eval_frame().
+
+define pystack
+    while $pc < Py_Main || $pc > Py_GetArgcArgv
+        if $pc > eval_frame && $pc < PyEval_EvalCodeEx
+            set $__fn = PyString_AsString(co->co_filename)
+            set $__n = PyString_AsString(co->co_name)
+            printf "%s (%d): %s\n",  $__fn, f->f_lineno, $__n
+        end
+        up-silently 1
+    end
+    select-frame 0
+end
diff --git a/Modules/main.c b/Modules/main.c
index 68a82c7be37..fc5773c07fb 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -452,6 +452,9 @@ Py_Main(int argc, char **argv)
 	return sts;
 }
 
+/* this is gonna seem *real weird*, but if you put some other code between
+   Py_Main() and Py_GetArgcArgv() you will need to adjust the test in the
+   while statement in Misc/gdbinit:ppystack */
 
 /* Make the *original* argc/argv available to other modules.
    This is rare, but it is needed by the secureware extension. */
diff --git a/Python/ceval.c b/Python/ceval.c
index c6fb0bf7e54..337184464f1 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -2445,6 +2445,10 @@ fast_yield:
 	return retval;
 }
 
+/* this is gonna seem *real weird*, but if you put some other code between
+   eval_frame() and PyEval_EvalCodeEx() you will need to adjust the test in
+   the if statement in Misc/gdbinit:ppystack */
+
 PyObject *
 PyEval_EvalCodeEx(PyCodeObject *co, PyObject *globals, PyObject *locals,
 	   PyObject **args, int argcount, PyObject **kws, int kwcount,