[pizlonator]

Lots of reasons why it is. I'll give you two.

1) It can't be that replacing 20 C/C++ shared objects with 20 Rust shared objects results in 20 copies of the Rust standard library and other dependencies that those Rust libraries pull in. But, today, that is what happens. For some situations, this is too much of a memory usage regression to be tolerable.

2) If you really have 20 libraries calling into one another using C ABI, then you end up with manual memory management and manual buffer offset management everywhere even if you rewrite the innards in Rust. So long as Rust doesn't have a safe ABI, the upside of a Rust rewrite might be too low in terms of safety/security gained to be worth doing

[zozbot234]

Many Rust core/standard library functions are trivial and inlining them is not really a concern. For those that do involve significant amount of code, C ABI-compatible code could be exported from some .so dynamic object, with only a small safe wrapper being statically linked.