secp256k1-sys 0.10.1

FFI for Pieter Wuille's `libsecp256k1` library.
Documentation 
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// SPDX-License-Identifier: CC0-1.0

//! # Build script

// Coding conventions
#![deny(non_upper_case_globals)]
#![deny(non_camel_case_types)]
#![deny(non_snake_case)]
#![deny(unused_mut)]
#![warn(missing_docs)]

extern crate cc;

use std::env;

fn main() {
    // Actual build
    let mut base_config = cc::Build::new();
    base_config.include("depend/secp256k1/")
               .include("depend/secp256k1/include")
               .include("depend/secp256k1/src")
               .flag_if_supported("-Wno-unused-function") // some ecmult stuff is defined but not used upstream
               .flag_if_supported("-Wno-unused-parameter") // patching out printf causes this warning
               .define("SECP256K1_API", Some(""))
               .define("ENABLE_MODULE_ECDH", Some("1"))
               .define("ENABLE_MODULE_SCHNORRSIG", Some("1"))
               .define("ENABLE_MODULE_EXTRAKEYS", Some("1"))
               .define("ENABLE_MODULE_ELLSWIFT", Some("1"))
               // upstream sometimes introduces calls to printf, which we cannot compile
               // with WASM due to its lack of libc. printf is never necessary and we can
               // just #define it away.
               .define("printf(...)", Some(""));

    if cfg!(feature = "lowmemory") {
        base_config.define("ECMULT_WINDOW_SIZE", Some("4")); // A low-enough value to consume negligible memory
        base_config.define("ECMULT_GEN_PREC_BITS", Some("2"));
    } else {
        base_config.define("ECMULT_GEN_PREC_BITS", Some("4"));
        base_config.define("ECMULT_WINDOW_SIZE", Some("15")); // This is the default in the configure file (`auto`)
    }
    base_config.define("USE_EXTERNAL_DEFAULT_CALLBACKS", Some("1"));
    #[cfg(feature = "recovery")]
    base_config.define("ENABLE_MODULE_RECOVERY", Some("1"));

    // WASM headers and size/align defines.
    if env::var("CARGO_CFG_TARGET_ARCH").unwrap() == "wasm32" {
        base_config.include("wasm/wasm-sysroot")
                   .file("wasm/wasm.c");
    }

    // secp256k1
    base_config.file("depend/secp256k1/contrib/lax_der_parsing.c")
               .file("depend/secp256k1/src/precomputed_ecmult_gen.c")
               .file("depend/secp256k1/src/precomputed_ecmult.c")
               .file("depend/secp256k1/src/secp256k1.c");

    if base_config.try_compile("libsecp256k1.a").is_err() {
        // Some embedded platforms may not have, eg, string.h available, so if the build fails
        // simply try again with the wasm sysroot (but without the wasm type sizes) in the hopes
        // that it works.
        base_config.include("wasm/wasm-sysroot");
        base_config.compile("libsecp256k1.a");
    }
}