Use env::var instead of cfg in some cases in build.rs (#961)

Co-authored-by: Thom Chiovoloni <chiovolonit@gmail.com>

libsqlite3-sys/Cargo.toml

@@ -40,6 +40,4 @@ winsqlite3 = ["min_sqlite_version_3_7_16"]
 bindgen = { version = "0.58", optional = true, default-features = false, features = ["runtime"] }
 pkg-config = { version = "0.3.19", optional = true }
 cc = { version = "1.0", optional = true }
-
-[target.'cfg(target_env = "msvc")'.build-dependencies]
 vcpkg = { version = "0.2", optional = true }

libsqlite3-sys/build.rs

@@ -1,6 +1,31 @@
 use std::env;
 use std::path::Path;
 
+/// Tells whether we're building for Windows. This is more suitable than a plain
+/// `cfg!(windows)`, since the latter does not properly handle cross-compilation
+///
+/// Note that there is no way to know at compile-time which system we'll be
+/// targetting, and this test must be made at run-time (of the build script) See
+/// https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts
+fn win_target() -> bool {
+    std::env::var("CARGO_CFG_WINDOWS").is_ok()
+}
+
+/// Tells whether we're building for Android.
+/// See [`win_target`]
+#[cfg(any(feature = "bundled", feature = "bundled-windows"))]
+fn android_target() -> bool {
+    std::env::var("CARGO_CFG_TARGET_OS").map_or(false, |v| v == "android")
+}
+
+/// Tells whether a given compiler will be used `compiler_name` is compared to
+/// the content of `CARGO_CFG_TARGET_ENV` (and is always lowercase)
+///
+/// See [`win_target`]
+fn is_compiler(compiler_name: &str) -> bool {
+    std::env::var("CARGO_CFG_TARGET_ENV").map_or(false, |v| v == compiler_name)
+}
+
 fn main() {
     let out_dir = env::var("OUT_DIR").unwrap();
     let out_path = Path::new(&out_dir).join("bindgen.rs");
@@ -12,40 +37,40 @@ fn main() {
         return;
     }
     if cfg!(feature = "sqlcipher") {
-        if cfg!(any(
+        if cfg!(feature = "bundled") || (win_target() && cfg!(feature = "bundled-windows")) {
-            feature = "bundled",
-            all(windows, feature = "bundled-windows")
-        )) {
             println!(
                 "cargo:warning=Builds with bundled SQLCipher are not supported. Searching for SQLCipher to link against. \
                  This can lead to issues if your version of SQLCipher is not up to date!");
         }
         build_linked::main(&out_dir, &out_path)
+    } else if cfg!(feature = "bundled") || (win_target() && cfg!(feature = "bundled-windows")) {
+        #[cfg(any(feature = "bundled", feature = "bundled-windows"))]
+        build_bundled::main(&out_dir, &out_path);
+        #[cfg(not(any(feature = "bundled", feature = "bundled-windows")))]
+        panic!("The runtime test should not run this branch, which has not compiled any logic.")
     } else {
-        // This can't be `cfg!` without always requiring our `mod build_bundled` (and
-        // thus `cc`)
-        #[cfg(any(feature = "bundled", all(windows, feature = "bundled-windows")))]
-        {
-            build_bundled::main(&out_dir, &out_path)
-        }
-        #[cfg(not(any(feature = "bundled", all(windows, feature = "bundled-windows"))))]
-        {
         build_linked::main(&out_dir, &out_path)
     }
-    }
 }
 
-#[cfg(any(feature = "bundled", all(windows, feature = "bundled-windows")))]
+#[cfg(any(feature = "bundled", feature = "bundled-windows"))]
 mod build_bundled {
     use std::env;
     use std::path::Path;
 
+    use super::{is_compiler, win_target};
+
     pub fn main(out_dir: &str, out_path: &Path) {
         if cfg!(feature = "sqlcipher") {
             // This is just a sanity check, the top level `main` should ensure this.
             panic!("Builds with bundled SQLCipher are not supported");
         }
 
+        if cfg!(feature = "bundled-windows") && !cfg!(feature = "bundled") && !win_target() {
+            // This is just a sanity check, the top level `main` should ensure this.
+            panic!("This module should not be used: we're not on Windows and the bundled feature has not been enabled");
+        }
+
         #[cfg(feature = "buildtime_bindgen")]
         {
             use super::{bindings, HeaderLocation};
@@ -86,7 +111,7 @@ mod build_bundled {
         // on android sqlite can't figure out where to put the temp files.
         // the bundled sqlite on android also uses `SQLITE_TEMP_STORE=3`.
         // https://android.googlesource.com/platform/external/sqlite/+/2c8c9ae3b7e6f340a19a0001c2a889a211c9d8b2/dist/Android.mk
-        if cfg!(target_os = "android") {
+        if super::android_target() {
             cfg.flag("-DSQLITE_TEMP_STORE=3");
         }
 
@@ -101,7 +126,7 @@ mod build_bundled {
         //
         // There may be other platforms that don't support `isnan`, they should be
         // tested for here.
-        if cfg!(target_env = "msvc") {
+        if is_compiler("msvc") {
             use cc::windows_registry::{find_vs_version, VsVers};
             let vs_has_nan = match find_vs_version() {
                 Ok(ver) => ver != VsVers::Vs12,
@@ -113,11 +138,11 @@ mod build_bundled {
         } else {
             cfg.flag("-DHAVE_ISNAN");
         }
-        if cfg!(not(target_os = "windows")) {
+        if !win_target() {
             cfg.flag("-DHAVE_LOCALTIME_R");
         }
         // Target wasm32-wasi can't compile the default VFS
-        if env::var("TARGET") == Ok("wasm32-wasi".to_string()) {
+        if is_compiler("wasm32-wasi") {
             cfg.flag("-DSQLITE_OS_OTHER")
                 // https://github.com/rust-lang/rust/issues/74393
                 .flag("-DLONGDOUBLE_TYPE=double");
@@ -199,20 +224,18 @@ impl From<HeaderLocation> for String {
 }
 
 mod build_linked {
-    #[cfg(all(feature = "vcpkg", target_env = "msvc"))]
+    #[cfg(feature = "vcpkg")]
     extern crate vcpkg;
 
-    use super::{bindings, env_prefix, HeaderLocation};
+    use super::{bindings, env_prefix, is_compiler, win_target, HeaderLocation};
     use std::env;
     use std::path::Path;
 
     pub fn main(_out_dir: &str, out_path: &Path) {
         let header = find_sqlite();
-        if cfg!(any(
+        if (cfg!(any(feature = "bundled_bindings", feature = "bundled"))
-            feature = "bundled_bindings",
+            || (win_target() && cfg!(feature = "bundled-windows")))
-            feature = "bundled",
+            && !cfg!(feature = "buildtime_bindgen")
-            all(windows, feature = "bundled-windows")
-        )) && !cfg!(feature = "buildtime_bindgen")
         {
             // Generally means the `bundled_bindings` feature is enabled
             // (there's also an edge case where we get here involving
@@ -242,7 +265,7 @@ mod build_linked {
         println!("cargo:rerun-if-env-changed={}_INCLUDE_DIR", env_prefix());
         println!("cargo:rerun-if-env-changed={}_LIB_DIR", env_prefix());
         println!("cargo:rerun-if-env-changed={}_STATIC", env_prefix());
-        if cfg!(all(feature = "vcpkg", target_env = "msvc")) {
+        if cfg!(feature = "vcpkg") && is_compiler("msvc") {
             println!("cargo:rerun-if-env-changed=VCPKGRS_DYNAMIC");
         }
 
@@ -252,7 +275,7 @@ mod build_linked {
         // on is available, for example.
         println!("cargo:link-target={}", link_lib);
 
-        if cfg!(all(windows, feature = "winsqlite3")) {
+        if win_target() && cfg!(feature = "winsqlite3") {
             println!("cargo:rustc-link-lib=dylib={}", link_lib);
             return HeaderLocation::Wrapper;
         }
@@ -298,8 +321,8 @@ mod build_linked {
         }
     }
 
-    #[cfg(all(feature = "vcpkg", target_env = "msvc"))]
     fn try_vcpkg() -> Option<HeaderLocation> {
+        if cfg!(feature = "vcpkg") && is_compiler("msvc") {
             // See if vcpkg can find it.
             if let Ok(mut lib) = vcpkg::Config::new().probe(link_lib()) {
                 if let Some(mut header) = lib.include_paths.pop() {
@@ -308,17 +331,15 @@ mod build_linked {
                 }
             }
             None
-    }
+        } else {
-
-    #[cfg(not(all(feature = "vcpkg", target_env = "msvc")))]
-    fn try_vcpkg() -> Option<HeaderLocation> {
             None
         }
+    }
 
     fn link_lib() -> &'static str {
         if cfg!(feature = "sqlcipher") {
             "sqlcipher"
-        } else if cfg!(all(windows, feature = "winsqlite3")) {
+        } else if win_target() && cfg!(feature = "winsqlite3") {
             "winsqlite3"
         } else {
             "sqlite3"
@@ -358,6 +379,8 @@ mod bindings {
     use std::io::Write;
     use std::path::Path;
 
+    use super::win_target;
+
     #[derive(Debug)]
     struct SqliteTypeChooser;
 
@@ -400,7 +423,7 @@ mod bindings {
         if cfg!(feature = "session") {
             bindings = bindings.clang_arg("-DSQLITE_ENABLE_SESSION");
         }
-        if cfg!(all(windows, feature = "winsqlite3")) {
+        if win_target() && cfg!(feature = "winsqlite3") {
             bindings = bindings
                 .clang_arg("-DBINDGEN_USE_WINSQLITE3")
                 .blocklist_item("NTDDI_.+")