From 94e54dcce75508c498478761b2e63d0ba9ff9657 Mon Sep 17 00:00:00 2001
From: Vladimir Prus <ghost@cs.msu.su>
Date: Sat, 27 Oct 2007 09:55:58 +0000
Subject: [PATCH] New Python rule -- 'backtrace'.

[SVN r40497]
---
 historic/jam/src/builtins.c | 26 ++++++++++++++++++++++++++
 historic/jam/src/compile.c  |  3 +++
 historic/jam/src/frames.c   |  1 -
 historic/jam/src/frames.h   |  8 ++++++++
 historic/jam/src/jam.c      |  5 +++++
 5 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/historic/jam/src/builtins.c b/historic/jam/src/builtins.c
index 4435fac24..802baf4fe 100644
--- a/historic/jam/src/builtins.c
+++ b/historic/jam/src/builtins.c
@@ -1775,6 +1775,32 @@ bjam_variable(PyObject* self, PyObject* args)
     return result;
 }
 
+PyObject*
+bjam_backtrace(PyObject* self, PyObject *args)
+{
+    PyObject *result = PyList_New(0);
+    struct frame *f = frame_before_python_call;
+
+    for(; f = f->prev;)
+    {
+        PyObject *tuple = PyTuple_New(4);
+        char* file;
+        int line;
+        char buf[32];
+        get_source_line( f->procedure, &file, &line );
+        sprintf( buf, "%d", line );
+        
+        /* PyTuple_SetItem steals reference. */
+        PyTuple_SetItem(tuple, 0, PyString_FromString(file));
+        PyTuple_SetItem(tuple, 1, PyString_FromString(buf));
+        PyTuple_SetItem(tuple, 2, PyString_FromString(f->module->name));
+        PyTuple_SetItem(tuple, 3, PyString_FromString(f->rulename));
+
+        PyList_Append(result, tuple);
+        Py_DECREF(tuple);
+    }
+    return result;
+}
 
 #endif
 
diff --git a/historic/jam/src/compile.c b/historic/jam/src/compile.c
index cd5a91941..4d64bb987 100644
--- a/historic/jam/src/compile.c
+++ b/historic/jam/src/compile.c
@@ -94,6 +94,8 @@ void backtrace_line( FRAME *frame );
 void print_source_line( PARSE* p );
 
 
+struct frame *frame_before_python_call;
+
 void frame_init( FRAME* frame )
 {
     frame->prev = 0;
@@ -827,6 +829,7 @@ call_python_function(RULE* r, FRAME* frame)
         PyTuple_SetItem(arguments, i, arg);
     }
 
+    frame_before_python_call = frame;
     py_result = PyObject_CallObject(r->python_function, arguments);
     Py_DECREF(arguments);
     if (py_result != NULL) {
diff --git a/historic/jam/src/frames.c b/historic/jam/src/frames.c
index c1bc1a03a..80b7197ed 100644
--- a/historic/jam/src/frames.c
+++ b/historic/jam/src/frames.c
@@ -7,7 +7,6 @@
 # include "frames.h"
 # include "lists.h"
 
-
 void frame_init( FRAME* frame )
 {
     frame->prev = 0;
diff --git a/historic/jam/src/frames.h b/historic/jam/src/frames.h
index 4921ac395..535784141 100644
--- a/historic/jam/src/frames.h
+++ b/historic/jam/src/frames.h
@@ -24,6 +24,14 @@ struct frame
     char*  rulename;
 };
 
+/* When call into Python is in progress, this
+   variable points to the bjam frame that
+   was current at the moment of call.  When the call
+   completes, the variable is not defined.  Further,
+   if Jam calls Python which calls Jam and so on,
+   this variable only keeps the most recent Jam frame.  */
+extern struct frame *frame_before_python_call;
+
 void frame_init( FRAME* ); /* implemented in compile.c */
 void frame_free( FRAME* ); /* implemented in compile.c */
 
diff --git a/historic/jam/src/jam.c b/historic/jam/src/jam.c
index 1533bfe57..d98b099c7 100644
--- a/historic/jam/src/jam.c
+++ b/historic/jam/src/jam.c
@@ -212,6 +212,9 @@ static void run_unit_tests()
 
     extern PyObject*
     bjam_variable(PyObject* self, PyObject* args);
+
+    extern PyObject*
+    bjam_backtrace(PyObject* self, PyObject *args);
 #endif
 
 int  main( int argc, char **argv, char **arg_environ )
@@ -349,6 +352,8 @@ int  main( int argc, char **argv, char **arg_environ )
                  "Defines a command line action."},
                 {"variable", bjam_variable, METH_VARARGS,
                  "Obtains a variable from bjam's global module."},
+                {"backtrace", bjam_backtrace, METH_VARARGS,
+                 "Returns bjam backtrace from the last call into Python."},
                 {NULL, NULL, 0, NULL}
             };