It's used at build time in 103 crates (of which 16 optionally, 23 directly). It's used only as a dev dependency in 2 crates.

Depender (with downloads and own rev deps) metadeps version
950 6 urcu2-sys build ^1
700 1 urcu2-bp-sys build ^1
650 1 urcu2-mb-sys build ^1
550 1 urcu2-memb-sys build ^1
550 1 urcu2-qsbr-sys build ^1
180 1 urcu2-cds-sys build ^1
1 ffms2-sys build ^1.1
1 speexdsp-sys build ^1.1
avformat-sys build ^1.1.2
sofia-sip build ^1.1.2
matio-sys build ^1.1
1 uhd-sys build ^1.1.2
intel-mediasdk-sys build ^1.1
libplacebo-sys build ^1.1
svt-av1-sys build ^1.1.2
1 e2p-sys build ^1.1.2
1 zmq-pw-sys build ^1
1 tmq-zmq-sys build ^1
1 libass-sys build ^1.1
urcu-sys build ^1.1.2
zbar-rs build ^1.1.2
zimg-sys build ^1.1
1 chromaprint_sys optional build ^1.1.2