manifest.c needs an eyeball or two

[Augie Fackler]

I clearly have a case of the dumb. I tried to fix this, and all I can do is get segfaults out the other end. Here’s what I’ve got after some beating my head against the wall:

diff --git a/mercurial/manifest.c b/mercurial/manifest.c
--- a/mercurial/manifest.c
+++ b/mercurial/manifest.c
@@ -704,9 +704,19 @@ static lazymanifest *lazymanifest_filter
 	copy->pydata = self->pydata;
 	Py_INCREF(self->pydata);
 	for (i = 0; i < self->numlines; i++) {
-		PyObject *arg = PyString_FromString(self->lines[i].start);
-		PyObject *arglist = PyTuple_Pack(1, arg);
-		PyObject *result = PyObject_CallObject(matchfn, arglist);
+		PyObject *arg = NULL, *arglist = NULL, *result = NULL;
+		arg = PyString_FromString(self->lines[i].start);
+		if (!arg) {
+			PyErr_SetString(PyExc_TypeError,
+					"couldn't pack filename");
+			return NULL;
+		}
+		arglist = PyTuple_Pack(1, arg);
+		Py_DECREF(arg);
+		if (!arglist) {
+			return NULL;
+		}
+		result = PyObject_CallObject(matchfn, arglist);
 		Py_DECREF(arglist);
 		Py_DECREF(arg);
 		/* if the callback raised an exception, just let it

(I found a handful of other non-checked error returns, but this one is causing problems if I try and fix it.)

> On Dec 12, 2015, at 11:07 PM, Bryan O'Sullivan <bos at serpentine.com> wrote:
> 
> Looking at use of some Python/C API functions, there are a few return values unchecked.
> 
> For instance, the first call to PyString_FromString in lazymanifest_filtercopy.

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