Spurious "error: could not find native static library `objc`, perhaps an -L flag is missing?" on macOS Big Sur

[adaszko]

Hi 👋

I'm experiencing this issue on macOS Big Sur when libusb1-sys crate's build.rs invokes pkg-config and gets this:

$ pkg-config --static --libs /usr/local/Cellar/libusb/1.0.26/lib/pkgconfig/libusb-1.0.pc
-L/usr/local/Cellar/libusb/1.0.26/lib -lusb-1.0 -lobjc -Wl,-framework,IOKit -Wl,-framework,CoreFoundation -Wl,-framework,Security

rustc seems then proceed to try to link libobjc:

$ [...] cargo build
   Compiling libusb1-sys v0.6.2 (/Users/adaszko/repos/rusb/libusb1-sys)
   Compiling rusb v0.9.1
error: could not find native static library `objc`, perhaps an -L flag is missing?

This issue is preventing me from building a statically linked libusb1-sys. Linking itself should still work, it's just that rustc's erroring out prevents the pipeline from getting to the linking step AFAICT.

EDIT: Sorry, I've removed a misleading points about dynamic linking stemming from my misunderstanding of the issue.

[madsmtm]

I suspect this may have been caused by not properly passing the macOS SDK to the linker, which will be fixed by #131477.

In the meantime, could you try doing xcrun cargo build, to ensure that SDKROOT is set?

[adaszko]

Sorry, I'm no longer working on this (it's been a while) so won't be able to test it. Unless someone else is affected I think the issue can be closed.