Thanks for the PR! I'm fine with merging in these changes as they don't conflict with anything else - but as we don't have any of these machines (neither ourselves nor in the CI) there's a good chance this will be broken again in the future. I also noticed you are making several changes in third party libraries we have inlined (moodycamel's concurrentqueue, httplib, fast_float). You may want to upstream these changes - otherwise once we update to a newer version the fixes will be lost.

Machine access - Yup, that can be a long journey, especially for zOS.
IBM Cloud has emulated zOS, but going for them isn't worth it just yet.
They're bare-bones VMs; some work will be required to set up the compilers etc.
https://community.ibm.com/community/user/ibmz-and-linuxone/blogs/sherri-hanna1/2022/09/22/i-can-do-it-mysef-wazi-as-a-service

Thank you! I'll submit PRs for those too..

@Mytherin, thanks again for accepting these changes.

but as we don't have any of these machines (neither ourselves nor in the CI) there's a good chance this will be broken again in the future.

Yes, I'll try to keep it in a working state. Do tag me in case anything gets broken because of this.
If it's something urgent, don't even hesitate to yank it out :)

Upstream PRs for reference. If you have time, could you see if these look ok?
yhirose/cpp-httplib#1581
cameron314/concurrentqueue#346
fastfloat/fast_float#207

Hi @Mytherin, could you pull this in please?

Thank you very much, apologies if I was rushing it.
I'm pretty new to contributing to the open source world 😅