Backport Tim's checkin 2.199:

Fix buglet reported on c.l.py:  map(fnc, file.xreadlines()) blows up.
Took away map()'s insistence that sequences support __len__, and cleaned
up the convoluted code that made it *look* like it really cared about
__len__ (in fact the old ->len field was only *used* as a flag bit, as
the main loop only looked at its sign bit, setting the field to -1 when
IndexError got raised; renamed the field to ->saw_IndexError instead).

diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 576447cabc83427e6f7f70c1883cc7eb36428e25..8814ff5a9fffa2182c7ff1d242d99b20d1b0fde1 100644 (file)
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -816,10 +816,10 @@ builtin_execfile(PyObject *self, PyObject *args)
        if (PyEval_GetNestedScopes()) {
                PyCompilerFlags cf;
                cf.cf_nested_scopes = 1;
-               res = PyRun_FileExFlags(fp, filename, Py_file_input, globals, 
+               res = PyRun_FileExFlags(fp, filename, Py_file_input, globals,
                                   locals, 1, &cf);
-       } else 
-               res = PyRun_FileEx(fp, filename, Py_file_input, globals, 
+       } else
+               res = PyRun_FileEx(fp, filename, Py_file_input, globals,
                                   locals, 1);
        return res;
 }
@@ -924,7 +924,7 @@ builtin_map(PyObject *self, PyObject *args)
        typedef struct {
                PyObject *seq;
                PySequenceMethods *sqf;
-               int len;
+               int saw_IndexError;
        } sequence;
 
        PyObject *func, *result;
@@ -952,6 +952,10 @@ builtin_map(PyObject *self, PyObject *args)
                goto Fail_2;
        }
 
+       /* Do a first pass to (a) verify the args are sequences; (b) set
+        * len to the largest of their lengths; (c) initialize the seqs
+        * descriptor vector.
+        */
        for (len = 0, i = 0, sqp = seqs; i < n; ++i, ++sqp) {
                int curlen;
                PySequenceMethods *sqf;
@@ -959,9 +963,10 @@ builtin_map(PyObject *self, PyObject *args)
                if ((sqp->seq = PyTuple_GetItem(args, i + 1)) == NULL)
                        goto Fail_2;
 
+               sqp->saw_IndexError = 0;
+
                sqp->sqf = sqf = sqp->seq->ob_type->tp_as_sequence;
                if (sqf == NULL ||
-                   sqf->sq_length == NULL ||
                    sqf->sq_item == NULL)
                {
                        static char errmsg[] =
@@ -973,9 +978,13 @@ builtin_map(PyObject *self, PyObject *args)
                        goto Fail_2;
                }
 
-               if ((curlen = sqp->len = (*sqp->sqf->sq_length)(sqp->seq)) < 0)
+               if (sqf->sq_length == NULL)
+                       /* doesn't matter -- make something up */
+                       curlen = 8;
+               else
+                       curlen = (*sqf->sq_length)(sqp->seq);
+               if (curlen < 0)
                        goto Fail_2;
-
                if (curlen > len)
                        len = curlen;
        }
@@ -983,6 +992,7 @@ builtin_map(PyObject *self, PyObject *args)
        if ((result = (PyObject *) PyList_New(len)) == NULL)
                goto Fail_2;
 
+       /* Iterate over the sequences until all have raised IndexError. */
        for (i = 0; ; ++i) {
                PyObject *alist, *item=NULL, *value;
                int any = 0;
@@ -995,7 +1005,7 @@ builtin_map(PyObject *self, PyObject *args)
                }
 
                for (j = 0, sqp = seqs; j < n; ++j, ++sqp) {
-                       if (sqp->len < 0) {
+                       if (sqp->saw_IndexError) {
                                Py_INCREF(Py_None);
                                item = Py_None;
                        }
@@ -1008,7 +1018,7 @@ builtin_map(PyObject *self, PyObject *args)
                                                PyErr_Clear();
                                                Py_INCREF(Py_None);
                                                item = Py_None;
-                                               sqp->len = -1;
+                                               sqp->saw_IndexError = 1;
                                        }
                                        else {
                                                goto Fail_0;