Changeset 60400

Timestamp:

07/01/2025 03:59:12 PM (8 months ago)

Author:

dmsnell

Message:

do_blocks(): Document transient-memory-leak optimization.

Adds explanatory comment indicating why the optimization was added
and guarding against accidental removal.

This is a documentation-only change and should include no functional
or visual changes.

Props audrasjb, dmsnell, joemcgill, sirlouen, westonruter, zunaid321.
Follow-up to [60316].
Fixes #63588.

File:

• trunk/src/wp-includes/blocks.php (modified) (1 diff)

trunk/src/wp-includes/blocks.php

@@ -2409 +2409 @@
     $output                = '';
 
+    /**
+     * Parsed blocks consist of a list of top-level blocks. Those top-level
+     * blocks may themselves contain nested inner blocks. However, every
+     * top-level block is rendered independently, meaning there are no data
+     * dependencies between them.
+     *
+     * Ideally, therefore, the parser would only need to parse one complete
+     * top-level block at a time, render it, and move on. Unfortunately, this
+     * is not possible with {@see \parse_blocks()} because it must parse the
+     * entire given document at once.
+     *
+     * While the current implementation prevents this optimization, it’s still
+     * possible to reduce the peak memory use when calls to `render_block()`
+     * on those top-level blocks are memory-heavy (which many of them are).
+     * By setting each parsed block to `NULL` after rendering it, any memory
+     * allocated during the render will be freed and reused for the next block.
+     * Before making this change, that memory was retained and would lead to
+     * out-of-memory crashes for certain posts that now run with this change.
+     */
     for ( $i = 0; $i < $top_level_block_count; $i++ ) {
         $output .= render_block( $blocks[ $i ] );