Complex features usually necessitate modularization, which is against the idea of the single file library. Modularization in c and c++ is very poor and based on having multiple files, some of which represent the interface and others that represent the implementation. I at least partly think this is his objection.
> > I've decided to write the whole µUBSan runtime as a single self-contained .c soure-code file, as it makes it easier for it to be reused by every interested party.
> I don't really get why people do this. Linking is one of the easiest and most broadly supported features of C environments on every platform.
Sure, this is true, and users already have to know how to link, unless they are #include'ing this, but still, a single file is much easier to share/distribute and use, and in any case, splitting up such a small file (by the standards of.. a number of open source projects I looked at, it's small) seems unnecessary.
I was just trying to explain what I thought his argument was against them, since I don't think he really explicitly stated it outside of generally speaking of maintenance issues. He just said he would prefer to contribute patches to a project that had multiple files and a makefile based build system.
I was assuming his argument was about the future directions the project could go, which I can see as being a valid criticism. As I said the main issue with a single file implementation is that potential users may end up using parts of the implementation instead of just the public facing interface you would like them to use.