From bca2b4cfeb3a98b150099a9d4ad488ba1b982ae0 Mon Sep 17 00:00:00 2001
From: Thomas Kowalski <thom.kowa@gmail.com>
Date: Wed, 27 May 2026 22:27:07 +0200
Subject: [PATCH 1/2] fix: eliminate memory leak in readline.c

---
 Modules/readline.c | 56 ++++++++++++++++++++++++++++------------------
 1 file changed, 34 insertions(+), 22 deletions(-)

diff --git a/Modules/readline.c b/Modules/readline.c
index 2cc3d40baa3aba1..11f14828de3466b 100644
--- a/Modules/readline.c
+++ b/Modules/readline.c
@@ -1357,29 +1357,41 @@ setup_readline(readlinestate *mod_state)
     if (using_libedit_emulation)
         rl_initialize();
 
-    /* Detect if libedit's readline emulation uses 0-based
-     * indexing or 1-based indexing.
-     */
-    add_history("1");
-    if (history_get(1) == NULL) {
-        libedit_history_start = 0;
-    } else {
-        libedit_history_start = 1;
-    }
-    /* Some libedit implementations use 1 based indexing on
-     * replace_history_entry where libreadline uses 0 based.
-     * The API our module presents is supposed to be 0 based.
-     * It's a mad mad mad mad world.
-     */
-    {
-        add_history("2");
-        HIST_ENTRY *old_entry = replace_history_entry(1, "X", NULL);
-        _py_free_history_entry_lock_held(old_entry);
-        HIST_ENTRY *item = history_get(libedit_history_start);
-        if (item && item->line && strcmp(item->line, "X")) {
-            libedit_append_replace_history_offset = 0;
+    if (using_libedit_emulation) {
+        /* Detect if libedit's readline emulation uses 0-based
+         * indexing or 1-based indexing.
+         */
+        add_history("1");
+        if (history_get(1) == NULL) {
+            libedit_history_start = 0;
         } else {
-            libedit_append_replace_history_offset = 1;
+            libedit_history_start = 1;
+        }
+        /* Some libedit implementations use 1 based indexing on
+         * replace_history_entry where libreadline uses 0 based.
+         * The API our module presents is supposed to be 0 based.
+         * It's a mad mad mad mad world.
+         */
+        {
+            add_history("2");
+            HIST_ENTRY *old_entry = replace_history_entry(1, "X", NULL);
+            _py_free_history_entry_lock_held(old_entry);
+            HIST_ENTRY *item = history_get(libedit_history_start);
+            if (item && item->line && strcmp(item->line, "X")) {
+                libedit_append_replace_history_offset = 0;
+            } else {
+                libedit_append_replace_history_offset = 1;
+            }
+        }
+        /* Use remove_history instead of clear_history to explicitly free
+         * each probe entry: some libedit builds do not free the strdup'd line
+         * strings inside clear_history, causing a small leak per process. */
+        while (history_length > 0) {
+            HIST_ENTRY *entry = remove_history(libedit_history_start);
+            if (entry == NULL) {
+                break;
+            }
+            _py_free_history_entry_lock_held(entry);
         }
     }
     clear_history();

From e1fafd06fa0958556530424c501466e6c897d498 Mon Sep 17 00:00:00 2001
From: Thomas Kowalski <thom.kowa@gmail.com>
Date: Wed, 27 May 2026 22:33:49 +0200
Subject: [PATCH 2/2] misc: add news entry

---
 .../Library/2026-05-27-22-33-25.gh-issue-150536.j0KkObbz.rst     | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-05-27-22-33-25.gh-issue-150536.j0KkObbz.rst

diff --git a/Misc/NEWS.d/next/Library/2026-05-27-22-33-25.gh-issue-150536.j0KkObbz.rst b/Misc/NEWS.d/next/Library/2026-05-27-22-33-25.gh-issue-150536.j0KkObbz.rst
new file mode 100644
index 000000000000000..041ccc2f5fe69de
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-27-22-33-25.gh-issue-150536.j0KkObbz.rst
@@ -0,0 +1 @@
+Fix a memory leak in the :mod:`readline` module on macOS.