zipfiles.ZipFile's internal ZipInfo entry cache has no internal bounds

Bug report

Bug description:

ZIP files with substantially many entries will exhaust memory when initialized using the zipfile module. As far as I know, there is no way to prevent this using the zipfile.ZipFile API.

The following code produces a ZIP file of 427 MB:

import zipfile
import tracemalloc

N = 5_000_000

tracemalloc.start()
try:
    with zipfile.ZipFile("test.zip", "w") as zf:
        for i in range(N):
            zf.writestr(str(i), "")
finally:
    m, _ = tracemalloc.get_traced_memory()
    print(f"{m >> 20} MB")

The following code on the produced ZIP file outputs 2408 MB on my machine:

import zipfile
import tracemalloc

tracemalloc.start()
try:
    with zipfile.ZipFile("test.zip", "r") as zf:
        pass
finally:
    m, _ = tracemalloc.get_traced_memory()
    print(f"{m >> 20} MB")

CPython versions tested on:

CPython main branch, 3.14

Operating systems tested on:

Linux

Linked PRs

• gh-153465

從 zipfile.ZipFile 進入點開始，針對包含大量項目的 ZIP 執行報告中的 tracemalloc 重現程式。開始前請檢視連結的 PR gh-153465，因為相關工作可能已經在進行中。完成的標準是：初始化不再允許內部 ZipInfo 項目快取耗盡記憶體，並且為報告中的大量項目案例加入測試涵蓋。