Can you give a case it fails? How it fixes the issue? I tried setting small page sizes and it all works.

Also I don't see the bug here. The idea is following if it is a long string allocate a separate page for it, otherwise use paged pool.

I also rerun some cases with small buffer size with valgrind to see if anythonig shows up and it does not.

Can you please explain the fix and what it fixes.

The reason for size * 2 - is to prevent wasting too much memory for large strings.

The problem is the case were the size is between page size and 2 * page size.

It's too small to allocate an own page with the correct size ( > 2 * page size case).

Then depending on the size it allocates a new page or uses an existing page. But since the size is > page size it always writes the string out of bounds because a page has a maximum size of page_size and that is smaller than size.

Note that I don't know why it worked with CppCMS 1.2.1 (same code in string_map.h). But with CppCMS 2.0.1 we started experiencing problems in only one of our applications. I found the origin of the problem with Valgrind's memcheck.