gh-146092: Raise MemoryError on allocation failure in _zoneinfo

[vstinner]

• Issue: Missing PyErr_NoMemory in _zoneinfo load_data and ts_to_local #146092

[StanFromIreland]

Please also fix:

https://github.com/python/cpython/blob/main/Modules/_zoneinfo.c#L1872-L1875

[vstinner]

Please also fix: https://github.com/python/cpython/blob/main/Modules/_zoneinfo.c#L1872-L1875

parse_transition_rule() is only used in parse_tz_str() and parse_tz_str() raises ValueError on parse_transition_rule() failure. Other parse_transition_rule() error paths don't set an exception. So I didn't add PyErr_NoMemory() in parse_transition_rule().

[StanFromIreland]

So I didn't add PyErr_NoMemory() in parse_transition_rule().

Can you please clarify why? The ValueError message may be misleading: "Malformed transition rule in TZ string"
I would update the check to only raise the ValueError if no other exception is already set.

[vstinner]

I would update the check to only raise the ValueError if no other exception is already set.

I tried that but I ended up with strange exceptions from a subfunction.

[StanFromIreland]

Oh yes, I see, I was able to reproduce that. Instead we could do:

         if (parse_transition_rule(&p, transitions[i])) {
-            PyErr_Format(PyExc_ValueError,
-                         "Malformed transition rule in TZ string: %R",
-                         tz_str_obj);
+            if (!PyErr_ExceptionMatches(PyExc_MemoryError)) {
+                PyErr_Format(PyExc_ValueError,
+                             "Malformed transition rule in TZ string: %R",
+                             tz_str_obj);
+            }
             goto error;
         }
     }

Since {day,calendar}rule_new (the subfunctions) only raise ValueErrors.

[vstinner]

Ok, I updated parse_transition_rule() to raise MemoryError and use if (!PyErr_ExceptionMatches(PyExc_MemoryError)) { in its caller.

[vstinner]

@StanFromIreland: Please review the updated PR.

[StanFromIreland]

LGTM, thanks Victor!

[miss-islington-app]

Thanks @vstinner for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-146223 is a backport of this pull request to the 3.14 branch.

[vstinner]

Merged, thanks for your reviews!

[bedevere-app]

GH-146224 is a backport of this pull request to the 3.13 branch.