Epic bug: pyexpat fiddles incorrectly with the systrace function. This is a hack to make it behave correctly with coverage.py. Fixes bug #10.

1 files changed, 19 insertions, 0 deletions

diff --git a/coverage/tracer.c b/coverage/tracer.c
index 50a25be2..15a17b2d 100644
--- a/coverage/tracer.c
+++ b/coverage/tracer.c
@@ -198,6 +198,25 @@ Tracer_trace(Tracer *self, PyFrameObject *frame, int what, PyObject *arg)
         break;

     }

 

+    /* UGLY HACK: for some reason, pyexpat invokes the systrace function directly.

+       It uses "pyexpat.c" as the filename, which is strange enough, but it calls

+       it incorrectly: when an exception passes through the C code, it calls trace

+       with an EXCEPTION, but never calls RETURN.  This throws off our bookkeeping.

+       To make things right, if this is an EXCEPTION from pyexpat.c, then inject

+       a RETURN event also.  If the bug in pyexpat.c gets fixed someday, we'll 

+       either have to put a version check here, or do something more sophisticated

+       to detect the EXCEPTION-without-RETURN case that has to be fixed up.

+    */

+    if (what == PyTrace_EXCEPTION) {

+        if (strstr(PyString_AS_STRING(frame->f_code->co_filename), "pyexpat.c")) {

+            /* Stupid pyexpat: pretend it gave us the RETURN it should have. */

+            SHOWLOG(self->depth, frame->f_lineno, frame->f_code->co_filename, "wrongexc");

+            if (Tracer_trace(self, frame, PyTrace_RETURN, arg) < 0) {

+                return -1;

+            }

+        }

+    }

+

     return 0;

 }