Binary dependencies allow programs to use precompiled libraries instead of compiling source code directly. This is common when calling C libraries from languages like Python, JavaScript, or Rust. An example is Python’s NumPy, which relies on the C library OpenBLAS for computations. These dependencies often go unnoticed because they aren't recorded in package manifests, leading to potential security risks and sustainability challenges for open-source projects. The article outlines how to call functions from a precompiled dynamic library, focusing on three methods: dynamic linking, dynamic loading, and dynamic linking with extension modules. It explains that dynamic linking simplifies the process by letting the operating system’s kernel handle function calls at runtime. When a program is compiled with a call to a function like `curl_easy_init` from `libcurl.so`, the linker doesn’t specify which library contains the symbol. Instead, it relies on the kernel to find the required function during execution. To illustrate these concepts, the article provides examples in Rust. Rust uses an attribute to link to a C library and requires the definition of C types for function calls. It emphasizes the importance of matching data types between languages, particularly when passing strings or other complex data structures. Overall, the article highlights the intricacies of managing binary dependencies across different programming languages and the need for careful handling of types and calls to ensure everything works seamlessly.