Use pkg-config

Cargo.toml

@@ -49,6 +49,7 @@ v5-38 = ["v5-35"]
 v5-40 = ["v5-38"]
 
 [build-dependencies]
+pkg-config = "0.3.27"
 vcpkg = "0.2.15"
 
 [package.metadata.vcpkg]

README.md

@@ -21,44 +21,52 @@ The `rustdoc` is available on [docs.rs](https://docs.rs/magic-sys).
 
 # Requirements
 
-This crate requires the `libmagic` C library in version 5.
+This crate requires the `libmagic` C library in version 5.39 or newer.
 
-You need to specify your `libmagic` version by activating the matching `magic-sys` feature.  
-Each API version has a crate feature like "v5-38" (v5.38 is also the default), see [Cargo.toml](Cargo.toml)  
-If you use a different version of `libmagic`, adjust your configuration:
-```toml
-[dependencies.magic-sys]
-version = "0.3"
-default-features = false
-features = ["v5-41"]
-```
-Note that those version features are additive, so "v5-41" implies "v5-40" and other previous versions.
+## libmagic
 
-`libmagic` needs to be installed in a standard location (also see [issue #1](https://github.com/robo9k/rust-magic-sys/issues/1)).
+If you don't want to configure the build, `libmagic` has to be available in a standard location
+for either `pkg-config` or `vcpkg`, see [Building](#Building).
 
-On a Debian based Linux system this can be achieved like this:
+On a Debian based Linux system such as Ubuntu this can be achieved like this:
 ```sh
 sudo apt-get install libmagic1 libmagic-dev
 ```
 
 On RHEL/Cent OS, Gentoo and others you will need to install the `file` package.
 
-
 On Mac OS X you can use [Homebrew](https://brew.sh/):
 ```sh
 brew install libmagic
 ```
 
 Feedback for Windows ([issue #2](https://github.com/robo9k/rust-magic-sys/issues/2)) support is appreciated!
 
-You can use Microsoft's [`vcpkg`](https://vcpkg.io) via [`vcpkg-rs`](https://docs.rs/vcpkg) and [`cargo-vcpkg`](https://crates.io/crates/cargo-vcpkg).
-If you choose the latter, that means you'll have to:
+You can use Microsoft's [`vcpkg`](https://vcpkg.io) via [`cargo-vcpkg`](https://crates.io/crates/cargo-vcpkg):
 ```sh
 cargo install cargo-vcpkg
 cargo vcpkg build
 ```
 Afterwards, you can `cargo build` etc. your crate as usual.
 
+## Version features
+
+The `libmagic` API is extended with new backwards-compatible features every now and then.\
+To use newly added `libmagic` functionality, you need to use a corresponding `libmagic` version.
+
+You need to specify your `libmagic` version by activating the matching `magic-sys` feature.\
+Each API version has a crate feature like "v5-38" (v5.38 is also the default), see [Cargo.toml](Cargo.toml)\
+If you use a different version of `libmagic`, adjust your configuration:
+```toml
+[dependencies.magic-sys]
+version = "0.3"
+default-features = false
+features = ["v5-41"]
+```
+Note that those version features are additive, so "v5-41" implies "v5-40" and other previous versions.
+
+If you want to use a newer/different `libmagic` version, you will have to [link it](#Building) accordingly.
+
 # MSRV
 
 The Minimum Supported Rust Version (MSRV) is Rust 1.54 or higher.
@@ -67,22 +75,55 @@ This version might be changed in the future, but it will be done with a crate ve
 
 # Building
 
-By default `libmagic` will be searched in the system library paths. If you need to use a different library or are cross-compiling, you can set the `MAGIC_DIR` and `MAGIC_STATIC` environment variables.
+To determine which `libmagic` to link against, this crate uses
+[`pkg-config`](https://www.freedesktop.org/wiki/Software/pkg-config/)
+and [`vcpkg`](https://vcpkg.io/).
+
+In general you can link statically or dynamically against `libmagic`.
+
+With static linkage your binary/library includes the `libmagic` code and _does not_ have a run-time dependency.
 
-## `MAGIC_DIR`, `<TARGET>_MAGIC_DIR`
-Tells `rustc` where to find `libmagic.so` / `libmagic.a`. Can have a target-specific prefix like `X86_64_UNKNOWN_LINUX_MUSL_MAGIC_DIR`
+With dynamic linkage your binary/library _does not_ include the `libmagic` code and _does_ have a run-time dependency on a `libmagic.dll` / `libmagic.so` / `libmagic.dylib` depending on your platform (Windows / Linux / macOS).\
+You might have to ship this `libmagic` shared library with your binary/library if you do not expect your users to have a compatible version installed on their system.
 
-## `MAGIC_STATIC`, `<TARGET>_MAGIC_STATIC`
-Controls static linking with `libmagic`. Enabled automatically if there's only a `libmagic.a` in the (provided) search path or if explicitly enabled like `MAGIC_STATIC=true`. Can have a target-specific prefix like `X86_64_UNKNOWN_LINUX_MUSL_MAGIC_STATIC`
+You might want to ship a copy of the default `libmagic` / `file` database with your binary/library if you do not expect your users to have a compatible `libmagic` installed on their system.
 
-Similarly `MAGIC_STATIC=false` can be used to choose to link `libmagic` dynamically.
-If unset but both libraries are available, the build will bail out with an error and you have to set one option explicitly.
+## pkg-config
+
+This uses the [`pkg-config` crate](https://docs.rs/pkg-config), so check its documentation for details.
+
+You can use e.g. the following environment variables:
+- `LIBMAGIC_NO_PKG_CONFIG` if set, will skip `pkg-config`
+- `LIBMAGIC_STATIC` if set, instructs `pkg-config` to link statically
+- `LIBMAGIC_DYNAMIC` if set, instructs `pkg-config` to link dynamically
+
+By default dynamic linkage is used.
 
 ## vcpkg
-The optional `vcpkg` integration has its own set of environment variables, see [`vcpkg` crate docs](https://docs.rs/vcpkg/#environment-variables).
-If you do not use `cargo vcpkg build`, you will have to either
-* `vcpkg install libmagic` and set the environment variables for your `vcpkg` root directory
-* `vcpkg integrate install` your `vcpkg` root user-wide
+
+This uses the [`vcpkg` crate](https://docs.rs/vcpkg), so check its documentation for details.
+
+You can use e.g. the following environment variables:
+- `VCPKGRS_NO_LIBMAGIC` if set, will skip `vcpkg`
+- `VCPKGRS_DYNAMIC` if set, instructs `vcpkg` to link dynamically
+
+By default static linkage is used.
+
+You can use `vcpkg` standalone or by using [`cargo-vcpkg`](https://crates.io/crates/cargo-vcpkg).
+
+If you do _not_ use `cargo vcpkg build`, you will have to either
+- `vcpkg install libmagic` and set the `VCPKG_ROOT` environment variable for your `vcpkg` root directory
+- `vcpkg integrate install` your `vcpkg` root user-wide
+
+## Custom
+
+If you skip both `pkg-config` and `vcpkg` the `magic-sys` build script will fail.\
+Especially linking statically to `libmagic` requires additional libraries that depend on your version and system.
+
+You can skip the `magic-sys` build script entirely by [overriding it](https://doc.rust-lang.org/cargo/reference/build-scripts.html#overriding-build-scripts).\
+This is an option if you want to use neither `pkg-config` nor `vcpkg`.
+
+The `magic-sys` crate does not offer to link a against a bundled `libmagic` version.
 
 # License
 

build.rs

@@ -1,63 +1,41 @@
-fn env(name: &str) -> Option<std::ffi::OsString> {
-    let target = std::env::var("TARGET").expect("Cargo didn't provide `TARGET` environment var");
-    let target = target.to_uppercase().replace("-", "_");
-    let prefixed_name = format!("{}_{}", target, name);
-    println!("cargo:rerun-if-env-changed={}", prefixed_name);
-    match std::env::var_os(prefixed_name) {
-        Some(v) => Some(v),
-        None => {
-            println!("cargo:rerun-if-env-changed={}", name);
-            std::env::var_os(name)
-        }
-    }
-}
+// SPDX-FileCopyrightText: © The `magic-sys` Rust crate authors
+// SPDX-License-Identifier: MIT OR Apache-2.0
 
 fn main() {
-    if let Some(magic_dir) = env("MAGIC_DIR").map(std::path::PathBuf::from) {
-        if !std::path::Path::new(&magic_dir).exists() {
-            panic!("Magic library directory {:?} does not exist", magic_dir);
-        }
-        println!(
-            "cargo:rustc-link-search=native={}",
-            magic_dir.to_string_lossy()
-        );
-
-        let static_lib = magic_dir.join("libmagic.a");
-        let shared_lib = magic_dir.join("libmagic.so");
-        match env("MAGIC_STATIC").as_ref().and_then(|s| s.to_str()) {
-            Some("false") | Some("FALSE") | Some("0") => {
-                if !shared_lib.exists() {
-                    panic!("No libmagic.so found in {:?}", magic_dir);
-                }
-                println!("cargo:rustc-link-lib=dylib=magic");
-            }
-            Some(_) => {
-                if !static_lib.exists() {
-                    panic!("No libmagic.a found in {:?}", magic_dir);
-                }
-                println!("cargo:rustc-link-lib=static=magic");
+    let lib = pkg_config::Config::new()
+        .atleast_version("5.39")
+        .probe("libmagic");
+    match lib {
+        Err(err) => match err {
+            pkg_config::Error::EnvNoPkgConfig(_) => {
+                println!("pkg-config skipped: {}", err);
             }
-            None => {
-                match (static_lib.exists(), shared_lib.exists()) {
-                    (false, false) => panic!("Neither libmagic.so, nor libmagic.a was found in {:?}", magic_dir),
-                    (true, false) => println!("cargo:rustc-link-lib=static=magic"),
-                    (false, true) => println!("cargo:rustc-link-lib=dylib=magic"),
-                    (true, true) => panic!("Both a static and a shared library were found in {:?}\nspecify a choice with `MAGIC_STATIC=true|false`", magic_dir),
-                }
+            _ => {
+                println!("cargo:warning=pkg-config failed: {}", err);
             }
+        },
+        Ok(lib) => {
+            println!("pkg-config success: {:?}", lib);
+            return;
         }
-    } else {
-        if let Err(err) = vcpkg::find_package("libmagic") {
-            println!("Could not find vcpkg package: {}", err);
-        } else if cfg!(windows) {
-            // workaround, see https://github.com/robo9k/rust-magic-sys/pull/16#issuecomment-949094327
-            println!("cargo:rustc-link-lib=shlwapi");
+    }
 
-            // vcpkg was successful, don't print anything else
+    let lib = vcpkg::find_package("libmagic");
+    match lib {
+        Err(err) => match err {
+            vcpkg::Error::DisabledByEnv(_) => {
+                println!("vcpkg skipped: {}", err);
+            }
+            _ => {
+                println!("cargo:warning=vcpkg failed: {}", err);
+            }
+        },
+        Ok(lib) => {
+            println!("vcpkg success: {:?}", lib);
             return;
         }
-
-        // default fall through: try linking dynamically to just `libmagic` without further config
-        println!("cargo:rustc-link-lib=dylib=magic");
     }
+
+    // if we're reach here, this means that either both pkg-config and vcpkg got skipped or both failed
+    panic!("could not link to `libmagic` with neither `pkg-config` nor `vcpkg`");
 }