libvlc-sys: import libvlc via raw-dylib on Windows
Windows has no import library to link against: the VLC installer and .zip ship libvlc.dll but no .lib. Previous workaround was to use vswhom + dumpbin + lib.exe to synthesise one at build time from the DLL's exports. rustc's `raw-dylib` linkage removes the need entirely, it generates the imports straight from the DLL name.master
Alaric Senat
parent
832a715d79
commit
f508cf7daf
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@ -2,22 +2,6 @@
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# It is not intended for manual editing.
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version = 3
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[[package]]
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name = "cc"
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version = "1.4.3"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "509591b7bcd67f4ef775afad7662703b4935daaa6ec0e5605cfb1090b32a2b6d"
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dependencies = [
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"find-msvc-tools",
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"shlex",
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]
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[[package]]
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name = "find-msvc-tools"
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version = "0.1.11"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "d45db016d36b838f563236e9193d0ee6ce38f3f68b6c94e914b4929c96bbb890"
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[[package]]
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name = "libc"
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version = "0.2.189"
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@ -30,7 +14,6 @@ version = "0.2.0"
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dependencies = [
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"libc",
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"pkg-config",
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"vswhom",
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]
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[[package]]
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@ -39,12 +22,6 @@ version = "0.3.34"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "f6b464fbc74e149a392436b17d523f769e057cb6877f6a5c4618bc6f11800548"
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[[package]]
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name = "shlex"
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version = "2.0.1"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "f8fadd59c855ef2080decdef8ff161eb6661b86933c9d82e5ba29dc602a55aba"
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[[package]]
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name = "vlc-rs"
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version = "0.3.0"
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@ -52,23 +29,3 @@ dependencies = [
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"libc",
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"libvlc-sys",
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]
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[[package]]
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name = "vswhom"
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version = "0.1.0"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "be979b7f07507105799e854203b470ff7c78a1639e330a58f183b5fea574608b"
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dependencies = [
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"libc",
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"vswhom-sys",
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]
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[[package]]
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name = "vswhom-sys"
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version = "0.1.3"
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source = "registry+https://github.com/rust-lang/crates.io-index"
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checksum = "fb067e4cbd1ff067d1df46c9194b5de0e98efd2810bbc95c5d5e5f25a3231150"
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dependencies = [
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"cc",
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"libc",
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]
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@ -23,6 +23,3 @@ libc = "0.2"
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[build-dependencies]
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pkg-config = "0.3"
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[target.'cfg(target_os = "windows")'.build-dependencies]
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vswhom = "0.1.0"
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@ -1610,6 +1610,7 @@ const _: () = {
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["Offset of field: libvlc_log_message_t::psz_message"]
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[::core::mem::offset_of!(libvlc_log_message_t, psz_message) - 32usize];
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};
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#[cfg_attr(windows, link(name = "libvlc", kind = "raw-dylib"))]
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unsafe extern "C" {
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pub fn libvlc_errmsg() -> *const libc::c_char;
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pub fn libvlc_clearerr();
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@ -1,5 +1,7 @@
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//! Build script for `libvlc-sys`, locates and links libvlc.
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use std::env;
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/// Minimum supported libvlc version.
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const MIN_LIBVLC_VERSION: &str = "3.0.0";
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@ -10,126 +12,21 @@ fn probe_libvlc() -> Result<pkg_config::Library, pkg_config::Error> {
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.probe("libvlc")
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}
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#[cfg(target_os = "windows")]
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mod windows {
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#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
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compile_error!("Only x86 and x86_64 are supported at the moment. Adding support for other architectures should be trivial.");
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use std::env;
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use std::ffi::OsString;
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use std::fs;
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use std::path::{Path, PathBuf};
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use std::process::Command;
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use vswhom::VsFindResult;
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pub fn link_vlc() {
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let vlc_path = vlc_path();
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let out_dir = PathBuf::from(env::var_os("OUT_DIR").unwrap());
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let vs = VsFindResult::search().expect("Could not locate Visual Studio");
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let vs_exe_path = PathBuf::from(
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vs.vs_exe_path
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.expect("Could not retrieve executable path for Visual Studio"),
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);
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generate_lib_from_dll(&out_dir, &vs_exe_path, &vlc_path);
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println!("cargo:rustc-link-search=native={}", out_dir.display());
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// NOTE: Without this directive, linking fails with:
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// ```
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// error LNK2019: unresolved external symbol vsnprintf referenced in function _{MangledSymbolName}
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// msvcrt.lib(vsnprintf.obj) : error LNK2001: unresolved external symbol vsnprintf
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// msvcrt.lib(vsnprintf.obj) : error LNK2001: unresolved external symbol _vsnprintf
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// ```
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// https://stackoverflow.com/a/34230122
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fn main() {
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// vsnprintf is inlined by the UCRT headers, so MSVC needs this to resolve
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// the symbol src/lib.rs declares. https://stackoverflow.com/a/34230122
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if env::var("CARGO_CFG_TARGET_ENV").unwrap_or_default() == "msvc" {
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println!("cargo:rustc-link-lib=dylib=legacy_stdio_definitions");
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}
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fn generate_lib_from_dll(out_dir: &Path, vs_exe_path: &Path, vlc_path: &Path) {
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// https://wiki.videolan.org/GenerateLibFromDll/
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let vs_dumpbin = vs_exe_path.join("dumpbin.exe");
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let vs_lib = vs_exe_path.join("lib.exe");
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let vlc_def_path = out_dir.join("libvlc.def");
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let vlc_import_lib = out_dir.join("vlc.lib");
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let libvlc = vlc_path.join("libvlc.dll");
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let exports = Command::new(vs_dumpbin)
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.current_dir(out_dir)
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.arg("/EXPORTS")
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.arg(libvlc.display().to_string().trim_end_matches(r"\"))
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.output()
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.unwrap();
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let exports = String::from_utf8(exports.stdout).unwrap();
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let mut vlc_def = String::from("EXPORTS\n");
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for line in exports.lines() {
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if let Some(line) = line.get(26..) {
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if line.starts_with("libvlc_") {
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vlc_def.push_str(line);
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vlc_def.push_str("\r\n");
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}
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}
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}
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fs::write(&vlc_def_path, vlc_def.into_bytes()).unwrap();
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// FIXME: Handle paths with spaces in them.
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Command::new(vs_lib)
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.current_dir(out_dir)
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.arg("/NOLOGO")
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.args(&[
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format!(
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r#"/DEF:{}"#,
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vlc_def_path.display().to_string().trim_end_matches(r"\")
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),
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format!(
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r#"/OUT:{}"#,
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vlc_import_lib.display().to_string().trim_end_matches(r"\")
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),
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format!(
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"/MACHINE:{}",
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match target_arch().as_str() {
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"x86" => "x86",
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"x86_64" => "x64",
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_ => unreachable!(),
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}
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),
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])
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.status()
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.expect("Failed to run lib.exe")
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.success()
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.then_some(())
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.expect("lib.exe failed to generate the vlc import library");
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// The bindings import from libvlc.dll directly via `raw-dylib`, so
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// Windows needs neither an import library nor a search path,
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// only the DLL at runtime.
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if env::var("CARGO_CFG_TARGET_OS").unwrap() == "windows" {
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return;
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}
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fn vlc_path() -> PathBuf {
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#[allow(unused_assignments)]
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let arch_path: Option<OsString> = match target_arch().as_str() {
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"x86" => env::var_os("VLC_LIB_DIR_X86"),
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"x86_64" => env::var_os("VLC_LIB_DIR_X86_64"),
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_ => unreachable!(),
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};
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arch_path
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.or_else(|| env::var_os("VLC_LIB_DIR"))
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.map(PathBuf::from)
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.expect("VLC_LIB_DIR not set")
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}
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fn target_arch() -> String {
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env::var("CARGO_CFG_TARGET_ARCH").unwrap()
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}
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}
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fn main() {
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// On success pkg-config has already emitted the link directives; only the
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// failure path needs handling.
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if let Err(err) = probe_libvlc() {
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#[cfg(target_os = "windows")]
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windows::link_vlc();
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#[cfg(not(target_os = "windows"))]
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panic!("libvlc (>= {}) not found: {:?}", MIN_LIBVLC_VERSION, err);
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}
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}
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@ -73,6 +73,13 @@ fn generate_bindings() {
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"a va_list spelling we do not know about survived"
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);
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// On Windows rustc can synthesise the imports straight from the DLL, so no
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// import library is needed. bindgen cannot emit the attribute itself.
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let generated = generated.replace(
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"unsafe extern \"C\" {",
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"#[cfg_attr(windows, link(name = \"libvlc\", kind = \"raw-dylib\"))]\nunsafe extern \"C\" {",
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);
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std::fs::write(&output, generated).expect("couldn't write bindings");
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println!("wrote {}", output.display());
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}
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