gh-110819: Fix ‘kind’ may be used uninitialized warning in longobject

[sobolevn]

I've also added an assert to make sure that both parameters writer and bytes_writer cannot be passed at the same time.

• Issue: "warning: ‘kind’ may be used uninitialized" in longobject.c #116592

• Issue: maybe-uninitialized compiler warnings on long_format_binary and long_to_decimal_string_internal #110819

[erlend-aasland]

@FFY00 has a similar PR up:

• GH-110819: fix maybe-uninitialized warnings on longobject.c #110821

[sobolevn]

Sorry, I've missed it! Differences:

• I'm using 0 as default, @FFY00 uses -1, both work in quite the same way
• I added assert for writer and bytes_writer params, @FFY00 added an assert for kind var

I am happy to close my PR and help @FFY00 finish the first PR if that works :)

[erlend-aasland]

This is a larger diff, but it avoids the initialisation:

Details

diff --git a/Objects/longobject.c b/Objects/longobject.c
index 2d1c6ad788..a631dc05b2 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -2197 +2196,0 @@ long_format_binary(PyObject *aa, int base, int alternate,
-    int kind;
@@ -2249 +2247,0 @@ long_format_binary(PyObject *aa, int base, int alternate,
-        kind = writer->kind;
@@ -2260 +2257,0 @@ long_format_binary(PyObject *aa, int base, int alternate,
-        kind = PyUnicode_KIND(v);
@@ -2321,8 +2317,0 @@ long_format_binary(PyObject *aa, int base, int alternate,
-    else if (kind == PyUnicode_1BYTE_KIND) {
-        Py_UCS1 *p;
-        WRITE_UNICODE_DIGITS(Py_UCS1);
-    }
-    else if (kind == PyUnicode_2BYTE_KIND) {
-        Py_UCS2 *p;
-        WRITE_UNICODE_DIGITS(Py_UCS2);
-    }
@@ -2330,3 +2319,14 @@ long_format_binary(PyObject *aa, int base, int alternate,
-        Py_UCS4 *p;
-        assert (kind == PyUnicode_4BYTE_KIND);
-        WRITE_UNICODE_DIGITS(Py_UCS4);
+        int kind = writer ? writer->kind : PyUnicode_KIND(v);
+        if (kind == PyUnicode_1BYTE_KIND) {
+            Py_UCS1 *p;
+            WRITE_UNICODE_DIGITS(Py_UCS1);
+        }
+        else if (kind == PyUnicode_2BYTE_KIND) {
+            Py_UCS2 *p;
+            WRITE_UNICODE_DIGITS(Py_UCS2);
+        }
+        else {
+            Py_UCS4 *p;
+            assert (kind == PyUnicode_4BYTE_KIND);
+            WRITE_UNICODE_DIGITS(Py_UCS4);
+        }

[FFY00]

I am happy to close my PR and help @FFY00 finish the first PR if that works :)

I don't have much bandwidth right now, we can close mine in favor of this PR.

[sobolevn]

@erlend-aasland yes, I liked your idea. I've implemented the change. Thank you!
@FFY00 thanks for working on this ❤️

[vstinner]

LGTM

[sobolevn]

Thanks everyone involved 👍

[bedevere-app]

GH-116648 is a backport of this pull request to the 3.12 branch.

[bedevere-app]

GH-116650 is a backport of this pull request to the 3.11 branch.