Memory leak in `extractBLOCKS` (`_as_blocks`): text object reference never released

[idlefella]

Description of the bug

Description

The extractBLOCKS code path leaks a Python object for every text, image, and vector block on every call. Since extractBLOCKS (a.k.a. page.get_text("blocks")) is commonly called once per page in bulk-processing loops, the leak accumulates quickly across large/multi-page documents.

Location

src/extra.i, in the recursive helper _as_blocks (around line 3501).

Root cause

The block tuple is populated like this:

PyObject *litem = PyTuple_New(7);
...
PyTuple_SET_ITEM(litem, 4, Py_BuildValue("O", text));   // <-- leak
...

text is created as a new reference, via either:

• JM_EscapeStrFromBuffer(res) (text blocks), or
• PyUnicode_FromFormat(...) (image / vector blocks).

The "O" format code in Py_BuildValue increments the refcount of text and returns a separate new object. That separate object is the one stolen into the tuple by PyTuple_SET_ITEM. The original text reference is then discarded on the next iteration:

text = NULL;

…without ever being decref'd. Net effect: text is leaked once per block.

The other six PyTuple_SET_ITEM calls in the same block are correct — Py_BuildValue("f"/"i", ...) creates a fresh object the tuple legitimately owns.

Fix

Hand the original text reference to the tuple instead of creating an extra one. Since PyTuple_SET_ITEM steals a reference, set it directly:

PyTuple_SET_ITEM(litem, 4, text);

(Equivalently, Py_BuildValue("N", text), where "N" steals rather than increments.)

Environment

• PyMuPDF: <fill in version, e.g. output of fitz.__doc__>
• OS / Python: <fill in>

How to reproduce the bug

Reproduction

import pymupdf, os, psutil
doc = pymupdf.open("some_multipage.pdf")
p = psutil.Process(os.getpid())
for i in range(200):
    for page in doc:
        page.get_text("blocks")
    rss_mb = p.memory_info().rss / (1024 * 1024)  # Convert to MiB
    print(f"Iteration {i + 1}: {rss_mb:.2f} MiB")  # grows steadily

PyMuPDF version

1.27.2.2

Operating system

Linux

Python version

3.12

[jatanb]

you can Locate the _as_blocks helper function

PyObject *litem = PyTuple_New(7);
...
PyTuple_SET_ITEM(litem, 4, Py_BuildValue("O", text));
...
text = NULL;