parse json OOM

[ddxxsx]

Description

I have a string, which is about 10MB in memory. However, when I use json::parse(), the memory cost is 1.6GB. I wonder if it's a bug?

Reproduction steps

A long string with chinese charater encoded with utf-8. call json j = json::parse(str); can trigger this bug.

Expected vs. actual results

lower memory cost.

Minimal code example

No response

Error messages

No response

Compiler and operating system

windows

Library version

branch: develop, commit hash: ee32bfc

Validation

• [X] The bug also occurs if the latest version from the develop branch is used.
• [X] I can successfully compile and run the unit tests.