std::sys::env::environ is causing linking problems on FreeBSD

[arrowd]

On FreeBSD the extern char** environ symbol is defined in the CRT rather than libc. This is known to cause linking problems for shared libraries when the linker is passed --no-undefined. The usual workaround for this issue is to resolve environ dynamically as suggested in https://reviews.freebsd.org/D30842#840642 I already pushed such a fix into LLVM and some other projects.

I've put up a minimal reproduction code at https://github.com/arrowd/rust-environ-problem Simply run make to get the linking error.

CC @asomers

[asomers]

@arrowd I have a patch that works. At least, your test case compiles. Can you extend the test case to do something at runtime?

[eggyal]

@rustbot label +A-dynamic-library +A-linkage +A-process +O-freebsd +T-libs -needs-triage

[arrowd]

@arrowd I have a patch that works. At least, your test case compiles. Can you extend the test case to do something at runtime?

Like this? arrowd/rust-environ-problem@3d19614

[asomers]

@arrowd this change works for me. It passes your test case, and it does not cause any regressions on a cdylib project of mine. Could you please test it?
https://github.com/asomers/rust/pull/new/environ-freebsd

[arrowd]

I patched our Rust port with this change and can confirm that it fixes the initial issue I had on the KDE FreeBSD CI builders. Thanks Alan!