Don't require two different MinGW environments to build the *_gnu imp…

…ort libraries

And at the same time, allow to use MinGW tools on any OS.

crates/tools/gnu/readme.md

@@ -1,21 +1,8 @@
 The Windows umbrella lib (targeting GNU tooling) is generated using the following steps:
 
 0. Ensure MSYS2 MinGW environment is installed (https://www.mingw-w64.org/downloads/)
-1. Ensure `~\.cargo\config` has the following blocks to override toolchain defaults (customize paths as needed):
-
-    ```toml
-    [target.i686-pc-windows-gnu]
-    linker = "C:\\msys64\\mingw32\\bin\\i686-w64-mingw32-gcc.exe"
-    ar = "C:\\msys64\\mingw32\\bin\\ar.exe"
-
-    [target.x86_64-pc-windows-gnu]
-    linker = "C:\\msys64\\mingw64\\bin\\x86_64-w64-mingw32-gcc.exe"
-    ar = "C:\\msys64\\mingw64\\bin\\ar.exe"
-    ```
-
-1. Open `MSYS2 MinGW 32-bit`
+1. Open `MSYS2 MinGW 64-bit`
 2. Execute: `pacman -Syuu --noconfirm` (repeat until no further updates available)
 3. Repeat step 1 if needed
 4. Navigate to crate root
-5. Execute: `PATH=$USERPROFILE/.cargo/bin:$PATH cargo run -p tool_gnu --target i686-pc-windows-gnu`
-6. Repeat steps 1-5, using the `MSYS MinGW 64-bit` environment and `x86_64-pc-windows-gnu` target
+5. Execute: `PATH=$USERPROFILE/.cargo/bin:$PATH cargo run -p tool_gnu -- all`

crates/tools/gnu/src/main.rs

@@ -1,28 +1,38 @@
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
+use std::process::{Command, Stdio};
 use std::io::prelude::*;
 
 fn main() {
-    let mut cmd = std::process::Command::new("where");
-    cmd.arg("dlltool.exe");
-
-    let output = cmd.output().unwrap();
-
-    if !output.status.success() {
-        println!("dlltool.exe not found");
-        return;
+    for cmd in ["dlltool", "ar", "objcopy"] {
+        if Command::new(cmd).stdout(Stdio::null()).stderr(Stdio::null()).spawn().is_err() {
+            eprintln!("Could not find {}. Is it in your $PATH?", cmd);
+            return;
+        }
+     }
+
+    const ALL_PLATFORMS: [&str; 2] = ["x86_64_gnu", "i686_gnu"];
+    let mut platforms = BTreeSet::new();
+    for platform in std::env::args().skip(1) {
+        if ALL_PLATFORMS.contains(&&*platform) {
+            platforms.insert(platform);
+        } else if platform == "all" {
+            platforms.extend(ALL_PLATFORMS.iter().map(|s| s.to_string()));
+        } else {
+            eprintln!("Unknown platform: {}", platform);
+            return;
+        }
     }
-
-    let output = unsafe { core::str::from_utf8_unchecked(&output.stdout) };
-
-    let platform = if output.contains("mingw64") {
-        "x86_64_gnu"
-    } else if output.contains("mingw32") {
-        "i686_gnu"
-    } else {
-        println!("mingw not found");
+    if platforms.is_empty() {
+        eprintln!("Please specify at least one platform or use 'all' argument");
         return;
     };
 
+    for platform in platforms {
+        build_platform(&platform);
+    }
+}
+
+fn build_platform(platform: &str) {
     println!("Platform: {}", platform);
 
     let libraries = lib::libraries();
@@ -70,7 +80,7 @@ EXPORTS
 
     drop(def);
 
-    let mut cmd = std::process::Command::new("dlltool");
+    let mut cmd = Command::new("dlltool");
     cmd.current_dir(output);
 
     if platform.eq("i686_gnu") {
@@ -81,6 +91,19 @@ EXPORTS
     cmd.arg(format!("{}.def", library));
     cmd.arg("-l");
     cmd.arg(format!("lib{}.a", library));
+    cmd.arg("-m");
+    cmd.arg(match platform {
+        "i686_gnu" => "i386",
+        "x86_64_gnu" => "i386:x86-64",
+        _ => unreachable!(),
+    });
+    // Work around https://sourceware.org/bugzilla/show_bug.cgi?id=29497
+    cmd.arg("-f");
+    cmd.arg(match platform {
+        "i686_gnu" => "--32",
+        "x86_64_gnu" => "--64",
+        _ => unreachable!(),
+    });
     // Ensure consistency in the prefixes used by dlltool.
     cmd.arg("-t");
     if library.contains('.') {
@@ -93,7 +116,7 @@ EXPORTS
     // Work around lack of determinism in dlltool output, and at the same time remove
     // unnecessary sections and symbols.
     std::fs::rename(output.join(format!("lib{}.a", library)), output.join("tmp.a")).unwrap();
-    let mut cmd = std::process::Command::new("objcopy");
+    let mut cmd = Command::new("objcopy");
     cmd.current_dir(output);
     cmd.arg("--remove-section=.bss");
     cmd.arg("--remove-section=.data");
@@ -127,7 +150,7 @@ fn build_mri(output: &std::path::Path, libraries: &BTreeMap<String, BTreeMap<Str
 
     mri.write_all(b"SAVE\nEND\n").unwrap();
 
-    let mut cmd = std::process::Command::new("ar");
+    let mut cmd = Command::new("ar");
     cmd.current_dir(output);
     cmd.arg("-M");
     cmd.stdin(std::fs::File::open(&mri_path).unwrap());