I see the point in theory, but it works incredibly well in practice. The specific technology has been used in production by major companies for years. It even carefully works around buggy software that makes incorrect assumptions for undefined behaviour.
(COI disclaimer: I used to work on this product; but I no longer have any stakes in it, financial or otherwise. I do still use the product, because it’s vastly superior to the alternatives.)
I actually did similar in production at Google, which i suspect is one of the companies you are referring to.
I'm even overall a fan of using JITted code in production for normally "static" languages.
But - i've never seen this sort of thing break through the significant resistance/feeling of taboo that often exists around doing that kind of thing in production, long term.
You will find companies here and there willing, sure. But writ large? It eventually goes away, even at companies willing to try it.
I do hope they get past all that, i just ... am skeptical.
Yes we have many large companies (Fortune Global 500) down to small organisations using our software with this kind of interception (see for example https://cuno.io/about-us/). It took us a decent sized team a lot of years to get right, because it is so very hard a problem to crack. But we think it is worth it. And for those who don't want to use such interception, we do offer a FUSE layer as well that still offers much higher performance than alternatives.
Just to clarify: no, I was referring to companies which are using products from the company behind cunoFS, and which share the actual code base of the functional interposition. My point is that while this technique is complex and brittle in general, this specific code-base is incredibly battle-tested and has proved itself even in fairly arcane configurations.
You’re definitely right about there being some amount of resistance, but functional interposition offers some compelling advantages over all alternative solutions in terms of ease of use and unparalleled performance.