Determine CFG_COMPILER_HOST_TRIPLE in build.rs

Author: luca-barbieri

src/librustc_session/build.rs

@@ -1,3 +1,146 @@
+use std::error::Error;
+use std::process::Command;
+
+fn output(cmd: &mut Command) -> Result<String, Box<dyn Error>> {
+    Ok(String::from_utf8(cmd.output()?.stdout)?.trim().into())
+}
+
+fn default_build_triple() -> Result<String, Box<dyn Error>> {
+    let ostype = output(Command::new("uname").arg("-s"));
+    let cputype = output(Command::new("uname").arg("-m"));
+    let (ostype, cputype) = match (ostype, cputype) {
+        (Ok(ostype), Ok(cputype)) => (ostype, cputype),
+        (ostype, cputype) => {
+            if cfg!(windows) {
+                return Ok("x86_64-pc-windows-msvc".into());
+            } else {
+                return ostype.and(cputype);
+            }
+        }
+    };
+
+    let mut cputype = cputype;
+    let ostype = match ostype.as_str() {
+        "Darwin" => "apple-darwin",
+        "DragonFly" => "unknown-dragonfly",
+        "FreeBSD" => "unknown-freebsd",
+        "Haiku" => "unknown-haiku",
+        "NetBSD" => "unknown-netbsd",
+        "OpenBSD" => "unknown-openbsd",
+        "Linux" => match output(Command::new("uname").arg("-o"))?.as_str() {
+            "Android" => "linux-android",
+            _ => "unknown-linux-gnu",
+        },
+        "SunOS" => {
+            cputype = output(Command::new("isainfo").arg("-k"))?;
+            "sun-solaris"
+        }
+        ostype if ostype.starts_with("MINGW") => {
+            cputype = if std::env::var("MSYSTEM").map(|x| x == "MINGW64").unwrap_or_default() {
+                "x86_64"
+            } else {
+                "i686"
+            }
+            .into();
+            "pc-windows-gnu"
+        }
+        ostype if ostype.starts_with("MSYS") => "pc-windows-gnu",
+        ostype if ostype.starts_with("CYGWIN_NT") => {
+            cputype = if ostype.ends_with("WOW64") { "x86_64" } else { "i686" }.into();
+            "pc-windows-gnu"
+        }
+        _ => {
+            return Err(format!("unknown OS type: {}", ostype).into());
+        }
+    };
+
+    if cputype == "powerpc" && ostype == "unknown-freebsd" {
+        cputype = output(Command::new("uname").arg("-p"))?;
+    }
+
+    let mut ostype: String = ostype.into();
+    let mut set_cputype_from_uname_p = false;
+    match cputype.as_str() {
+        "BePC" => "i686",
+        "aarch64" => "aarch64",
+        "amd64" => "x86_64",
+        "arm64" => "aarch64",
+        "i386" => "i686",
+        "i486" => "i686",
+        "i686" => "i686",
+        "i786" => "i686",
+        "powerpc" => "powerpc",
+        "powerpc64" => "powerpc64",
+        "powerpc64le" => "powerpc64le",
+        "ppc" => "powerpc",
+        "ppc64" => "powerpc64",
+        "ppc64le" => "powerpc64le",
+        "s390x" => "s390x",
+        "x64" => "x86_64",
+        "x86" => "i686",
+        "x86-64" => "x86_64",
+        "x86_64" => "x86_64",
+        "xscale" | "arm" => match ostype.as_str() {
+            "linux-android" => {
+                ostype = "linux-androideabi".into();
+                "arm"
+            }
+            "unknown-freebsd" => {
+                ostype = "unknown-freebsd".into();
+                set_cputype_from_uname_p = true;
+                ""
+            }
+            _ => cputype.as_str(),
+        },
+        "armv6l" => {
+            match ostype.as_str() {
+                "linux-android" => {
+                    ostype = "linux-androideabi".into();
+                }
+                _ => {
+                    ostype += "eabihf";
+                }
+            };
+            "arm"
+        }
+        "armv7l" | "armv8l" => {
+            match ostype.as_str() {
+                "linux-android" => {
+                    ostype = "linux-androideabi".into();
+                }
+                _ => {
+                    ostype += "eabihf";
+                }
+            };
+            "armv7"
+        }
+        "mips" => {
+            if cfg!(target_endian = "big") {
+                "mips"
+            } else {
+                "mipsel"
+            }
+        }
+        "mips64" => {
+            ostype += "abi64";
+            if cfg!(target_endian = "big") { "mips64" } else { "mips64el" }
+        }
+        "sparc" => "sparc",
+        "sparcv9" => "sparcv9",
+        "sparc64" => "sparc64",
+        _ => {
+            return Err(format!("unknown cpu type: {}", cputype).into());
+        }
+    };
+    let cputype = if set_cputype_from_uname_p {
+        output(Command::new("uname").arg("-p"))?
+    } else {
+        cputype.into()
+    };
+
+    Ok(format!("{}-{}", cputype, ostype))
+}
+
 fn main() {
     println!("cargo:rerun-if-changed=build.rs");
     println!("cargo:rerun-if-env-changed=CFG_RELEASE");
@@ -9,4 +152,11 @@ fn main() {
     println!("cargo:rerun-if-env-changed=CFG_VIRTUAL_RUST_SOURCE_BASE_DIR");
     println!("cargo:rerun-if-env-changed=CFG_COMPILER_HOST_TRIPLE");
     println!("cargo:rerun-if-env-changed=CFG_LIBDIR_RELATIVE");
+
+    if std::env::var_os("CFG_COMPILER_HOST_TRIPLE").is_none() {
+        println!(
+            "cargo:rustc-env=CFG_COMPILER_HOST_TRIPLE={}",
+            default_build_triple().expect("Unable to determine build triple not found")
+        )
+    };
 }