use std::env; fn main() { // OpenSSL >= 1.1.0 can be initialized concurrently and is initialized correctly by libcurl. // <= 1.0.2 need locking callbacks, which are provided by openssl_sys::init(). let use_openssl = match env::var("DEP_OPENSSL_VERSION_NUMBER") { Ok(version) => { let version = u64::from_str_radix(&version, 16).unwrap(); if version < 0x1_01_00_00_0 { println!("cargo:rustc-cfg=need_openssl_init"); } true } Err(_) => false, }; if use_openssl { // The system libcurl should have the default certificate paths configured. if env::var_os("DEP_CURL_STATIC").is_some() { println!("cargo:rustc-cfg=need_openssl_probe"); } } }