Fix issue #1689458 by teaching frame_setlineno how to jump to the first line of

a code object.

diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index a8f51638399194aadb98e80623ef8259db48e124..f5b8dbffb457088d866ec47c527678b66123adce 100644 (file)
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -740,6 +740,27 @@ class JumpTestCase(unittest.TestCase):
     def test_19_no_jump_without_trace_function(self):
         no_jump_without_trace_function()
 
+    def test_jump_to_firstlineno(self):
+        # This tests that PDB can jump back to the first line in a
+        # file.  See issue #1689458.  It can only be triggered in a
+        # function call if the function is defined on a single line.
+        code = compile("""
+# Comments don't count.
+output.append(2)  # firstlineno is here.
+output.append(3)
+output.append(4)
+""", "<fake module>", "exec")
+        class fake_function:
+            func_code = code
+            jump = (2, 0)
+        tracer = JumpTracer(fake_function)
+        sys.settrace(tracer.trace)
+        namespace = {"output": []}
+        exec code in namespace
+        sys.settrace(None)
+        self.compare_jump_output([2, 3, 2, 3, 4], namespace["output"])
+
+
 def test_main():
     test_support.run_unittest(
         TraceTestCase,

diff --git a/Objects/frameobject.c b/Objects/frameobject.c
index 5e54585f67bc2828fb73a60cc0c65dc93bca486d..ad31fc5dd49116afccf3c92302721d6019f37fa9 100644 (file)
--- a/Objects/frameobject.c
+++ b/Objects/frameobject.c
@@ -140,20 +140,26 @@ frame_setlineno(PyFrameObject *f, PyObject* p_new_lineno)
                             new_lineno);
                return -1;
        }
-
-       /* Find the bytecode offset for the start of the given line, or the
-        * first code-owning line after it. */
-       PyString_AsStringAndSize(f->f_code->co_lnotab, &lnotab, &lnotab_len);
-       addr = 0;
-       line = f->f_code->co_firstlineno;
-       new_lasti = -1;
-       for (offset = 0; offset < lnotab_len; offset += 2) {
-               addr += lnotab[offset];
-               line += lnotab[offset+1];
-               if (line >= new_lineno) {
-                       new_lasti = addr;
-                       new_lineno = line;
-                       break;
+       else if (new_lineno == f->f_code->co_firstlineno) {
+               new_lasti = 0;
+               new_lineno = f->f_code->co_firstlineno;
+       }
+       else {
+               /* Find the bytecode offset for the start of the given
+                * line, or the first code-owning line after it. */
+               PyString_AsStringAndSize(f->f_code->co_lnotab,
+                                        &lnotab, &lnotab_len);
+               addr = 0;
+               line = f->f_code->co_firstlineno;
+               new_lasti = -1;
+               for (offset = 0; offset < lnotab_len; offset += 2) {
+                       addr += lnotab[offset];
+                       line += lnotab[offset+1];
+                       if (line >= new_lineno) {
+                               new_lasti = addr;
+                               new_lineno = line;
+                               break;
+                       }
                }
        }