Workspace dylib with missing shared object dependencies

[nickbabcock]

On latest stable / nightlies on linux:

Creating a new project and the modifying the generated Cargo.toml:

[lib]
crate-type = ["dylib"]

Produces an .so with the following shared objects dependencies

ldd target/debug/lib*.so
        linux-vdso.so.1 =>  (0x00007ffd3d1e6000)
        libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007f21e02f1000)
        librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007f21e00e9000)
        libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f21dfecb000)
        libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007f21dfcb4000)
        libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f21df8ed000)
        /lib64/ld-linux-x86-64.so.2 (0x00005638697ba000)

I expected that if we added a workspace member that also is a dylib, both would have the same shared object dependencies

However, if you add a workspace member (we'll create an inner project that is also a dylib and neither crate depends on each other). A cargo clean && cargo build --all later and the shared object dependencies for both change:

ldd target/debug/lib*.so
target/debug/libinner.so:
        linux-vdso.so.1 =>  (0x00007fff0cc8a000)
        libstd-29fb1fb52cf57377.so => not found
target/debug/libtemp.so:
        linux-vdso.so.1 =>  (0x00007fff38950000)
        libstd-29fb1fb52cf57377.so => not found

This issue came up when searching for previous issues: #39487 but seems somewhat windows and $PATH related, so didn't seem relevant.

*cargo clean was a necessary step as the library wouldn't be rebuilt otherwise.

[nickbabcock]

Ah, for single crate repos dylib will link against posted objects, but this is only for backwards compatibility. Cargo workspaces assume that it's a sign to renege compatibility. Crates that will be opened by dlopen or the like need to have a crate type of cdylib. So no bug anywhere 😆