Update gcc crate to 0.3.54

Import subrepo gcc/:gcc at dc329205d54b53a45ab66368aed265b68fe7f261

1 files changed, 682 insertions, 209 deletions

diff --git a/gcc/src/lib.rs b/gcc/src/lib.rs
index 7d19e13..4c5e724 100644
--- a/gcc/src/lib.rs
+++ b/gcc/src/lib.rs
@@ -10,35 +10,30 @@
 //!
 //! The purpose of this crate is to provide the utility functions necessary to
 //! compile C code into a static archive which is then linked into a Rust crate.
-//! The top-level `compile_library` function serves as a convenience and more
-//! advanced configuration is available through the `Config` builder.
+//! Configuration is available through the `Build` struct.
 //!
 //! This crate will automatically detect situations such as cross compilation or
 //! other environment variables set by Cargo and will build code appropriately.
 //!
-//! # Examples
-//!
-//! Use the default configuration:
+//! The crate is not limited to C code, it can accept any source code that can
+//! be passed to a C or C++ compiler. As such, assembly files with extensions
+//! `.s` (gcc/clang) and `.asm` (MSVC) can also be compiled.
 //!
-//! ```no_run
-//! extern crate gcc;
+//! [`Build`]: struct.Build.html
 //!
-//! fn main() {
-//!     gcc::compile_library("libfoo.a", &["src/foo.c"]);
-//! }
-//! ```
+//! # Examples
 //!
-//! Use more advanced configuration:
+//! Use the `Build` struct to compile `src/foo.c`:
 //!
 //! ```no_run
 //! extern crate gcc;
 //!
 //! fn main() {
-//!     gcc::Config::new()
-//!                 .file("src/foo.c")
-//!                 .define("FOO", Some("bar"))
-//!                 .include("src")
-//!                 .compile("libfoo.a");
+//!     gcc::Build::new()
+//!                .file("src/foo.c")
+//!                .define("FOO", Some("bar"))
+//!                .include("src")
+//!                .compile("foo");
 //! }
 //! ```
 
@@ -57,6 +52,13 @@ use std::process::{Command, Stdio, Child};
 use std::io::{self, BufReader, BufRead, Read, Write};
 use std::thread::{self, JoinHandle};
 
+#[doc(hidden)]
+#[deprecated(since="0.3.51", note="gcc::Config has been renamed to gcc::Build")]
+pub type Config = Build;
+
+#[cfg(feature = "parallel")]
+use std::sync::Mutex;
+
 // These modules are all glue to support reading the MSVC version from
 // the registry and from COM interfaces
 #[cfg(windows)]
@@ -72,11 +74,13 @@ mod setup_config;
 pub mod windows_registry;
 
 /// Extra configuration to pass to gcc.
-pub struct Config {
+#[derive(Clone, Debug)]
+pub struct Build {
     include_directories: Vec<PathBuf>,
     definitions: Vec<(String, Option<String>)>,
     objects: Vec<PathBuf>,
     flags: Vec<String>,
+    flags_supported: Vec<String>,
     files: Vec<PathBuf>,
     cpp: bool,
     cpp_link_stdlib: Option<Option<String>>,
@@ -92,6 +96,46 @@ pub struct Config {
     cargo_metadata: bool,
     pic: Option<bool>,
     static_crt: Option<bool>,
+    shared_flag: Option<bool>,
+    static_flag: Option<bool>,
+    warnings_into_errors: bool,
+    warnings: bool,
+}
+
+/// Represents the types of errors that may occur while using gcc-rs.
+#[derive(Clone, Debug)]
+enum ErrorKind {
+    /// Error occurred while performing I/O.
+    IOError,
+    /// Invalid architecture supplied.
+    ArchitectureInvalid,
+    /// Environment variable not found, with the var in question as extra info.
+    EnvVarNotFound,
+    /// Error occurred while using external tools (ie: invocation of compiler).
+    ToolExecError,
+    /// Error occurred due to missing external tools.
+    ToolNotFound,
+}
+
+/// Represents an internal error that occurred, with an explaination.
+#[derive(Clone, Debug)]
+pub struct Error {
+    /// Describes the kind of error that occurred.
+    kind: ErrorKind,
+    /// More explaination of error that occurred.
+    message: String,
+}
+
+impl Error {
+    fn new(kind: ErrorKind, message: &str) -> Error {
+        Error { kind: kind, message: message.to_owned() }
+    }
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Error {
+        Error::new(ErrorKind::IOError, &format!("{}", e))
+    }
 }
 
 /// Configuration used to represent an invocation of a C compiler.
@@ -101,6 +145,7 @@ pub struct Config {
 /// This can be used to further configure other build systems (e.g. forward
 /// along CC and/or CFLAGS) or the `to_command` method can be used to run the
 /// compiler itself.
+#[derive(Clone, Debug)]
 pub struct Tool {
     path: PathBuf,
     args: Vec<OsString>,
@@ -113,7 +158,7 @@ pub struct Tool {
 /// Each family of tools differs in how and what arguments they accept.
 ///
 /// Detection of a family is done on best-effort basis and may not accurately reflect the tool.
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 enum ToolFamily {
     /// Tool is GNU Compiler Collection-like.
     Gnu,
@@ -151,6 +196,27 @@ impl ToolFamily {
             ToolFamily::Clang => "-E",
         }
     }
+
+    /// What the flags to enable all warnings
+    fn warnings_flags(&self) -> &'static [&'static str] {
+        static MSVC_FLAGS: &'static [&'static str] = &["/W4"];
+        static GNU_CLANG_FLAGS: &'static [&'static str] = &["-Wall", "-Wextra"];
+
+        match *self {
+            ToolFamily::Msvc => &MSVC_FLAGS,
+            ToolFamily::Gnu |
+            ToolFamily::Clang => &GNU_CLANG_FLAGS,
+        }
+    }
+
+    /// What the flag to turn warning into errors
+    fn warnings_to_errors_flag(&self) -> &'static str {
+        match *self {
+            ToolFamily::Msvc => "/WX",
+            ToolFamily::Gnu |
+            ToolFamily::Clang => "-Werror"
+        }
+    }
 }
 
 /// Compile a library from the given set of input C files.
@@ -164,27 +230,34 @@ impl ToolFamily {
 /// # Example
 ///
 /// ```no_run
-/// gcc::compile_library("libfoo.a", &["foo.c", "bar.c"]);
+/// gcc::compile_library("foo", &["foo.c", "bar.c"]);
 /// ```
+#[deprecated]
+#[doc(hidden)]
 pub fn compile_library(output: &str, files: &[&str]) {
-    let mut c = Config::new();
+    let mut c = Build::new();
     for f in files.iter() {
         c.file(*f);
     }
     c.compile(output);
 }
 
-impl Config {
+impl Build {
     /// Construct a new instance of a blank set of configuration.
     ///
-    /// This builder is finished with the `compile` function.
-    pub fn new() -> Config {
-        Config {
+    /// This builder is finished with the [`compile`] function.
+    ///
+    /// [`compile`]: struct.Build.html#method.compile
+    pub fn new() -> Build {
+        Build {
             include_directories: Vec::new(),
             definitions: Vec::new(),
             objects: Vec::new(),
             flags: Vec::new(),
+            flags_supported: Vec::new(),
             files: Vec::new(),
+            shared_flag: None,
+            static_flag: None,
             cpp: false,
             cpp_link_stdlib: None,
             cpp_set_stdlib: None,
@@ -199,48 +272,229 @@ impl Config {
             cargo_metadata: true,
             pic: None,
             static_crt: None,
+            warnings: true,
+            warnings_into_errors: false,
         }
     }
 
     /// Add a directory to the `-I` or include path for headers
-    pub fn include<P: AsRef<Path>>(&mut self, dir: P) -> &mut Config {
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// use std::path::Path;
+    ///
+    /// let library_path = Path::new("/path/to/library");
+    ///
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .include(library_path)
+    ///            .include("src")
+    ///            .compile("foo");
+    /// ```
+    pub fn include<P: AsRef<Path>>(&mut self, dir: P) -> &mut Build {
         self.include_directories.push(dir.as_ref().to_path_buf());
         self
     }
 
     /// Specify a `-D` variable with an optional value.
-    pub fn define(&mut self, var: &str, val: Option<&str>) -> &mut Config {
-        self.definitions.push((var.to_string(), val.map(|s| s.to_string())));
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .define("FOO", "BAR")
+    ///            .define("BAZ", None)
+    ///            .compile("foo");
+    /// ```
+    pub fn define<'a, V: Into<Option<&'a str>>>(&mut self, var: &str, val: V) -> &mut Build {
+        self.definitions.push((var.to_string(), val.into().map(|s| s.to_string())));
         self
     }
 
     /// Add an arbitrary object file to link in
-    pub fn object<P: AsRef<Path>>(&mut self, obj: P) -> &mut Config {
+    pub fn object<P: AsRef<Path>>(&mut self, obj: P) -> &mut Build {
         self.objects.push(obj.as_ref().to_path_buf());
         self
     }
 
     /// Add an arbitrary flag to the invocation of the compiler
-    pub fn flag(&mut self, flag: &str) -> &mut Config {
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .flag("-ffunction-sections")
+    ///            .compile("foo");
+    /// ```
+    pub fn flag(&mut self, flag: &str) -> &mut Build {
         self.flags.push(flag.to_string());
         self
     }
 
+    fn ensure_check_file(&self) -> Result<PathBuf, Error> {
+        let out_dir = self.get_out_dir()?;
+        let src = if self.cpp {
+            out_dir.join("flag_check.cpp")
+        } else {
+            out_dir.join("flag_check.c")
+        };
+
+        if !src.exists() {
+            let mut f = fs::File::create(&src)?;
+            write!(f, "int main(void) {{ return 0; }}")?;
+        }
+
+        Ok(src)
+    }
+
+    fn is_flag_supported(&self, flag: &str) -> Result<bool, Error> {
+        let out_dir = self.get_out_dir()?;
+        let src = self.ensure_check_file()?;
+        let obj = out_dir.join("flag_check");
+        let target = self.get_target()?;
+        let mut cfg = Build::new();
+        cfg.flag(flag)
+           .target(&target)
+           .opt_level(0)
+           .host(&target)
+           .debug(false)
+           .cpp(self.cpp);
+        let compiler = cfg.try_get_compiler()?;
+        let mut cmd = compiler.to_command();
+        command_add_output_file(&mut cmd, &obj, target.contains("msvc"), false);
+        cmd.arg(&src);
+
+        let output = cmd.output()?;
+        Ok(output.stderr.is_empty())
+    }
+
+    /// Add an arbitrary flag to the invocation of the compiler if it supports it
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .flag_if_supported("-Wlogical-op") // only supported by GCC
+    ///            .flag_if_supported("-Wunreachable-code") // only supported by clang
+    ///            .compile("foo");
+    /// ```
+    pub fn flag_if_supported(&mut self, flag: &str) -> &mut Build {
+        self.flags_supported.push(flag.to_string());
+        self
+    }
+
+    /// Set the `-shared` flag.
+    ///
+    /// When enabled, the compiler will produce a shared object which can
+    /// then be linked with other objects to form an executable.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .shared_flag(true)
+    ///            .compile("libfoo.so");
+    /// ```
+
+    pub fn shared_flag(&mut self, shared_flag: bool) -> &mut Build {
+        self.shared_flag = Some(shared_flag);
+        self
+    }
+
+    /// Set the `-static` flag.
+    ///
+    /// When enabled on systems that support dynamic linking, this prevents
+    /// linking with the shared libraries.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .shared_flag(true)
+    ///            .static_flag(true)
+    ///            .compile("foo");
+    /// ```
+    pub fn static_flag(&mut self, static_flag: bool) -> &mut Build {
+        self.static_flag = Some(static_flag);
+        self
+    }
+
     /// Add a file which will be compiled
-    pub fn file<P: AsRef<Path>>(&mut self, p: P) -> &mut Config {
+    pub fn file<P: AsRef<Path>>(&mut self, p: P) -> &mut Build {
         self.files.push(p.as_ref().to_path_buf());
         self
     }
 
+    /// Add files which will be compiled
+    pub fn files<P>(&mut self, p: P) -> &mut Build
+        where P: IntoIterator,
+              P::Item: AsRef<Path> {
+        for file in p.into_iter() {
+            self.file(file);
+        }
+        self
+    }
+
     /// Set C++ support.
     ///
     /// The other `cpp_*` options will only become active if this is set to
     /// `true`.
-    pub fn cpp(&mut self, cpp: bool) -> &mut Config {
+    pub fn cpp(&mut self, cpp: bool) -> &mut Build {
         self.cpp = cpp;
         self
     }
 
+    /// Set warnings into errors flag.
+    ///
+    /// Disabled by default.
+    ///
+    /// Warning: turning warnings into errors only make sense
+    /// if you are a developer of the crate using gcc-rs.
+    /// Some warnings only appear on some architecture or
+    /// specific version of the compiler. Any user of this crate,
+    /// or any other crate depending on it, could fail during
+    /// compile time.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .warnings_into_errors(true)
+    ///            .compile("libfoo.a");
+    /// ```
+    pub fn warnings_into_errors(&mut self, warnings_into_errors: bool) -> &mut Build {
+        self.warnings_into_errors = warnings_into_errors;
+        self
+    }
+
+    /// Set warnings flags.
+    ///
+    /// Adds some flags:
+    /// - "/Wall" for MSVC.
+    /// - "-Wall", "-Wextra" for GNU and Clang.
+    ///
+    /// Enabled by default.
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .warnings(false)
+    ///            .compile("libfoo.a");
+    /// ```
+    pub fn warnings(&mut self, warnings: bool) -> &mut Build {
+        self.warnings = warnings;
+        self
+    }
+
     /// Set the standard library to link against when compiling with C++
     /// support.
     ///
@@ -252,8 +506,22 @@ impl Config {
     /// otherwise cargo will link against the specified library.
     ///
     /// The given library name must not contain the `lib` prefix.
-    pub fn cpp_link_stdlib(&mut self, cpp_link_stdlib: Option<&str>) -> &mut Config {
-        self.cpp_link_stdlib = Some(cpp_link_stdlib.map(|s| s.into()));
+    ///
+    /// Common values:
+    /// - `stdc++` for GNU
+    /// - `c++` for Clang
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .shared_flag(true)
+    ///            .cpp_link_stdlib("stdc++")
+    ///            .compile("libfoo.so");
+    /// ```
+    pub fn cpp_link_stdlib<'a, V: Into<Option<&'a str>>>(&mut self, cpp_link_stdlib: V) -> &mut Build {
+        self.cpp_link_stdlib = Some(cpp_link_stdlib.into().map(|s| s.into()));
         self
     }
 
@@ -277,7 +545,21 @@ impl Config {
     /// be used, otherwise `-stdlib` is added to the compile invocation.
     ///
     /// The given library name must not contain the `lib` prefix.
-    pub fn cpp_set_stdlib(&mut self, cpp_set_stdlib: Option<&str>) -> &mut Config {
+    ///
+    /// Common values:
+    /// - `stdc++` for GNU
+    /// - `c++` for Clang
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .cpp_set_stdlib("c++")
+    ///            .compile("libfoo.a");
+    /// ```
+    pub fn cpp_set_stdlib<'a, V: Into<Option<&'a str>>>(&mut self, cpp_set_stdlib: V) -> &mut Build {
+        let cpp_set_stdlib = cpp_set_stdlib.into();
         self.cpp_set_stdlib = cpp_set_stdlib.map(|s| s.into());
         self.cpp_link_stdlib(cpp_set_stdlib);
         self
@@ -287,7 +569,16 @@ impl Config {
     ///
     /// This option is automatically scraped from the `TARGET` environment
     /// variable by build scripts, so it's not required to call this function.
-    pub fn target(&mut self, target: &str) -> &mut Config {
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .target("aarch64-linux-android")
+    ///            .compile("foo");
+    /// ```
+    pub fn target(&mut self, target: &str) -> &mut Build {
         self.target = Some(target.to_string());
         self
     }
@@ -296,7 +587,16 @@ impl Config {
     ///
     /// This option is automatically scraped from the `HOST` environment
     /// variable by build scripts, so it's not required to call this function.
-    pub fn host(&mut self, host: &str) -> &mut Config {
+    ///
+    /// # Example
+    ///
+    /// ```no_run
+    /// gcc::Build::new()
+    ///            .file("src/foo.c")
+    ///            .host("arm-linux-gnueabihf")
+    ///            .compile("foo");
+    /// ```
+    pub fn host(&mut self, host: &str) -> &mut Build {
         self.host = Some(host.to_string());
         self
     }
@@ -305,7 +605,7 @@ impl Config {
     ///
     /// This option is automatically scraped from the `OPT_LEVEL` environment
     /// variable by build scripts, so it's not required to call this function.
-    pub fn opt_level(&mut self, opt_level: u32) -> &mut Config {
+    pub fn opt_level(&mut self, opt_level: u32) -> &mut Build {
         self.opt_level = Some(opt_level.to_string());
         self
     }
@@ -314,7 +614,7 @@ impl Config {
     ///
     /// This option is automatically scraped from the `OPT_LEVEL` environment
     /// variable by build scripts, so it's not required to call this function.
-    pub fn opt_level_str(&mut self, opt_level: &str) -> &mut Config {
+    pub fn opt_level_str(&mut self, opt_level: &str) -> &mut Build {
         self.opt_level = Some(opt_level.to_string());
         self
     }
@@ -325,7 +625,7 @@ impl Config {
     /// This option is automatically scraped from the `PROFILE` environment
     /// variable by build scripts (only enabled when the profile is "debug"), so
     /// it's not required to call this function.
-    pub fn debug(&mut self, debug: bool) -> &mut Config {
+    pub fn debug(&mut self, debug: bool) -> &mut Build {
         self.debug = Some(debug);
         self
     }
@@ -335,7 +635,7 @@ impl Config {
     ///
     /// This option is automatically scraped from the `OUT_DIR` environment
     /// variable by build scripts, so it's not required to call this function.
-    pub fn out_dir<P: AsRef<Path>>(&mut self, out_dir: P) -> &mut Config {
+    pub fn out_dir<P: AsRef<Path>>(&mut self, out_dir: P) -> &mut Build {
         self.out_dir = Some(out_dir.as_ref().to_owned());
         self
     }
@@ -345,7 +645,7 @@ impl Config {
     /// This option is automatically determined from the target platform or a
     /// number of environment variables, so it's not required to call this
     /// function.
-    pub fn compiler<P: AsRef<Path>>(&mut self, compiler: P) -> &mut Config {
+    pub fn compiler<P: AsRef<Path>>(&mut self, compiler: P) -> &mut Build {
         self.compiler = Some(compiler.as_ref().to_owned());
         self
     }
@@ -355,13 +655,21 @@ impl Config {
     /// This option is automatically determined from the target platform or a
     /// number of environment variables, so it's not required to call this
     /// function.
-    pub fn archiver<P: AsRef<Path>>(&mut self, archiver: P) -> &mut Config {
+    pub fn archiver<P: AsRef<Path>>(&mut self, archiver: P) -> &mut Build {
         self.archiver = Some(archiver.as_ref().to_owned());
         self
     }
     /// Define whether metadata should be emitted for cargo allowing it to
     /// automatically link the binary. Defaults to `true`.
-    pub fn cargo_metadata(&mut self, cargo_metadata: bool) -> &mut Config {
+    ///
+    /// The emitted metadata is:
+    ///
+    ///  - `rustc-link-lib=static=`*compiled lib*
+    ///  - `rustc-link-search=native=`*target folder*
+    ///  - When target is MSVC, the ATL-MFC libs are added via `rustc-link-search=native=`
+    ///  - When C++ is enabled, the C++ stdlib is added via `rustc-link-lib`
+    ///
+    pub fn cargo_metadata(&mut self, cargo_metadata: bool) -> &mut Build {
         self.cargo_metadata = cargo_metadata;
         self
     }
@@ -370,7 +678,7 @@ impl Config {
     ///
     /// This option defaults to `false` for `windows-gnu` targets and
     /// to `true` for all other targets.
-    pub fn pic(&mut self, pic: bool) -> &mut Config {
+    pub fn pic(&mut self, pic: bool) -> &mut Build {
         self.pic = Some(pic);
         self
     }
@@ -378,14 +686,13 @@ impl Config {
     /// Configures whether the /MT flag or the /MD flag will be passed to msvc build tools.
     ///
     /// This option defaults to `false`, and affect only msvc targets.
-    pub fn static_crt(&mut self, static_crt: bool) -> &mut Config {
+    pub fn static_crt(&mut self, static_crt: bool) -> &mut Build {
         self.static_crt = Some(static_crt);
         self
     }
 
-
     #[doc(hidden)]
-    pub fn __set_env<A, B>(&mut self, a: A, b: B) -> &mut Config
+    pub fn __set_env<A, B>(&mut self, a: A, b: B) -> &mut Build
         where A: AsRef<OsStr>,
               B: AsRef<OsStr>
     {
@@ -395,31 +702,42 @@ impl Config {
 
     /// Run the compiler, generating the file `output`
     ///
-    /// The name `output` must begin with `lib` and end with `.a`
-    pub fn compile(&self, output: &str) {
-        assert!(output.starts_with("lib"));
-        assert!(output.ends_with(".a"));
-        let lib_name = &output[3..output.len() - 2];
-        let dst = self.get_out_dir();
+    /// This will return a result instead of panicing; see compile() for the complete description.
+    pub fn try_compile(&self, output: &str) -> Result<(), Error> {
+        let (lib_name, gnu_lib_name) = if output.starts_with("lib") && output.ends_with(".a") {
+                (&output[3..output.len() - 2], output.to_owned())
+            } else {
+                let mut gnu = String::with_capacity(5 + output.len());
+                gnu.push_str("lib");
+                gnu.push_str(&output);
+                gnu.push_str(".a");
+                (output, gnu)
+            };
+        let dst = self.get_out_dir()?;
 
         let mut objects = Vec::new();
         let mut src_dst = Vec::new();
         for file in self.files.iter() {
             let obj = dst.join(file).with_extension("o");
             let obj = if !obj.starts_with(&dst) {
-                dst.join(obj.file_name().unwrap())
+                dst.join(obj.file_name().ok_or_else(|| Error::new(ErrorKind::IOError, "Getting object file details failed."))?)
             } else {
                 obj
             };
-            fs::create_dir_all(&obj.parent().unwrap()).unwrap();
+
+            match obj.parent() {
+                Some(s) => fs::create_dir_all(s)?,
+                None => return Err(Error::new(ErrorKind::IOError, "Getting object file details failed.")),
+            };
+
             src_dst.push((file.to_path_buf(), obj.clone()));
             objects.push(obj);
         }
-        self.compile_objects(&src_dst);
-        self.assemble(lib_name, &dst.join(output), &objects);
+        self.compile_objects(&src_dst)?;
+        self.assemble(lib_name, &dst.join(gnu_lib_name), &objects)?;
 
-        if self.get_target().contains("msvc") {
-            let compiler = self.get_base_compiler();
+        if self.get_target()?.contains("msvc") {
+            let compiler = self.get_base_compiler()?;
             let atlmfc_lib = compiler.env()
                 .iter()
                 .find(|&&(ref var, _)| var.as_os_str() == OsStr::new("LIB"))
@@ -435,20 +753,39 @@ impl Config {
             }
         }
 
-        self.print(&format!("cargo:rustc-link-lib=static={}",
-                            &output[3..output.len() - 2]));
+        self.print(&format!("cargo:rustc-link-lib=static={}", lib_name));
         self.print(&format!("cargo:rustc-link-search=native={}", dst.display()));
 
         // Add specific C++ libraries, if enabled.
         if self.cpp {
-            if let Some(stdlib) = self.get_cpp_link_stdlib() {
+            if let Some(stdlib) = self.get_cpp_link_stdlib()? {
                 self.print(&format!("cargo:rustc-link-lib={}", stdlib));
             }
         }
+
+        Ok(())
+    }
+
+    /// Run the compiler, generating the file `output`
+    ///
+    /// The name `output` should be the name of the library.  For backwards compatibility,
+    /// the `output` may start with `lib` and end with `.a`.  The Rust compilier will create
+    /// the assembly with the lib prefix and .a extension.  MSVC will create a file without prefix,
+    /// ending with `.lib`.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `output` is not formatted correctly or if one of the underlying
+    /// compiler commands fails. It can also panic if it fails reading file names
+    /// or creating directories.
+    pub fn compile(&self, output: &str) {
+        if let Err(e) = self.try_compile(output) {
+            fail(&e.message);
+        }
     }
 
     #[cfg(feature = "parallel")]
-    fn compile_objects(&self, objs: &[(PathBuf, PathBuf)]) {
+    fn compile_objects(&self, objs: &[(PathBuf, PathBuf)]) -> Result<(), Error> {
         use self::rayon::prelude::*;
 
         let mut cfg = rayon::Configuration::new();
@@ -459,24 +796,36 @@ impl Config {
         }
         drop(rayon::initialize(cfg));
 
+        let results: Mutex<Vec<Result<(), Error>>> = Mutex::new(Vec::new());
+
         objs.par_iter().with_max_len(1)
-            .for_each(|&(ref src, ref dst)| self.compile_object(src, dst));
+            .for_each(|&(ref src, ref dst)| results.lock().unwrap().push(self.compile_object(src, dst)));
+
+        // Check for any errors and return the first one found.
+        for result in results.into_inner().unwrap().iter() {
+            if result.is_err() {
+                return result.clone();
+            }
+        }
+
+        Ok(())
     }
 
     #[cfg(not(feature = "parallel"))]
-    fn compile_objects(&self, objs: &[(PathBuf, PathBuf)]) {
+    fn compile_objects(&self, objs: &[(PathBuf, PathBuf)]) -> Result<(), Error> {
         for &(ref src, ref dst) in objs {
-            self.compile_object(src, dst);
+            self.compile_object(src, dst)?;
         }
+        Ok(())
     }
 
-    fn compile_object(&self, file: &Path, dst: &Path) {
+    fn compile_object(&self, file: &Path, dst: &Path) -> Result<(), Error> {
         let is_asm = file.extension().and_then(|s| s.to_str()) == Some("asm");
-        let msvc = self.get_target().contains("msvc");
+        let msvc = self.get_target()?.contains("msvc");
         let (mut cmd, name) = if msvc && is_asm {
-            self.msvc_macro_assembler()
+            self.msvc_macro_assembler()?
         } else {
-            let compiler = self.get_compiler();
+            let compiler = self.try_get_compiler()?;
             let mut cmd = compiler.to_command();
             for &(ref a, ref b) in self.env.iter() {
                 cmd.env(a, b);
@@ -484,46 +833,62 @@ impl Config {
             (cmd,
              compiler.path
                  .file_name()
-                 .unwrap()
+                 .ok_or_else(|| Error::new(ErrorKind::IOError, "Failed to get compiler path."))?
                  .to_string_lossy()
                  .into_owned())
         };
-        if msvc && is_asm {
-            cmd.arg("/Fo").arg(dst);
-        } else if msvc {
-            let mut s = OsString::from("/Fo");
-            s.push(&dst);
-            cmd.arg(s);
-        } else {
-            cmd.arg("-o").arg(&dst);
-        }
+        command_add_output_file(&mut cmd, dst, msvc, is_asm);
         cmd.arg(if msvc { "/c" } else { "-c" });
         cmd.arg(file);
 
-        run(&mut cmd, &name);
+        run(&mut cmd, &name)?;
+        Ok(())
     }
 
-    /// Run the compiler, returning the macro-expanded version of the input files.
-    ///
-    /// This is only relevant for C and C++ files.
-    pub fn expand(&self) -> Vec<u8> {
-        let compiler = self.get_compiler();
+    /// This will return a result instead of panicing; see expand() for the complete description.
+    pub fn try_expand(&self) -> Result<Vec<u8>, Error> {
+        let compiler = self.try_get_compiler()?;
         let mut cmd = compiler.to_command();
         for &(ref a, ref b) in self.env.iter() {
             cmd.env(a, b);
         }
         cmd.arg(compiler.family.expand_flag());
+
+        assert!(self.files.len() <= 1,
+                "Expand may only be called for a single file");
+
         for file in self.files.iter() {
             cmd.arg(file);
         }
 
         let name = compiler.path
             .file_name()
-            .unwrap()
+            .ok_or_else(|| Error::new(ErrorKind::IOError, "Failed to get compiler path."))?
             .to_string_lossy()
             .into_owned();
 
-        run_output(&mut cmd, &name)
+        Ok(run_output(&mut cmd, &name)?)
+    }
+
+    /// Run the compiler, returning the macro-expanded version of the input files.
+    ///
+    /// This is only relevant for C and C++ files.
+    ///
+    /// # Panics
+    /// Panics if more than one file is present in the config, or if compiler
+    /// path has an invalid file name.
+    ///
+    /// # Example
+    /// ```no_run
+    /// let out = gcc::Build::new()
+    ///                       .file("src/foo.c")
+    ///                       .expand();
+    /// ```
+    pub fn expand(&self) -> Vec<u8> {
+        match self.try_expand() {
+            Err(e) => fail(&e.message),
+            Ok(v) => v,
+        }
     }
 
     /// Get the compiler that's in use for this configuration.
@@ -540,11 +905,25 @@ impl Config {
     /// conventions for this path, e.g. looking at the explicitly set compiler,
     /// environment variables (a number of which are inspected here), and then
     /// falling back to the default configuration.
+    ///
+    /// # Panics
+    ///
+    /// Panics if an error occurred while determining the architecture.
     pub fn get_compiler(&self) -> Tool {
-        let opt_level = self.get_opt_level();
-        let target = self.get_target();
+        match self.try_get_compiler() {
+            Ok(tool) => tool,
+            Err(e) => fail(&e.message),
+        }
+    }
 
-        let mut cmd = self.get_base_compiler();
+    /// Get the compiler that's in use for this configuration.
+    ///
+    /// This will return a result instead of panicing; see get_compiler() for the complete description.
+    pub fn try_get_compiler(&self) -> Result<Tool, Error> {
+        let opt_level = self.get_opt_level()?;
+        let target = self.get_target()?;
+
+        let mut cmd = self.get_base_compiler()?;
         let nvcc = cmd.path.file_name()
             .and_then(|p| p.to_str()).map(|p| p.contains("nvcc"))
             .unwrap_or(false);
@@ -580,7 +959,14 @@ impl Config {
             }
             ToolFamily::Gnu |
             ToolFamily::Clang => {
-                cmd.args.push(format!("-O{}", opt_level).into());
+                // arm-linux-androideabi-gcc 4.8 shipped with Android NDK does
+                // not support '-Oz'
+                if opt_level == "z" && cmd.family != ToolFamily::Clang {
+                    cmd.args.push("-Os".into());
+                } else {
+                    cmd.args.push(format!("-O{}", opt_level).into());
+                }
+
                 if !nvcc {
                     cmd.args.push("-ffunction-sections".into());
                     cmd.args.push("-fdata-sections".into());
@@ -618,7 +1004,7 @@ impl Config {
                     cmd.args.push("-m64".into());
                 }
 
-                if target.contains("musl") {
+                if self.static_flag.is_none() && target.contains("musl") {
                     cmd.args.push("-static".into());
                 }
 
@@ -695,7 +1081,14 @@ impl Config {
         if target.contains("-ios") {
             // FIXME: potential bug. iOS is always compiled with Clang, but Gcc compiler may be
             // detected instead.
-            self.ios_flags(&mut cmd);
+            self.ios_flags(&mut cmd)?;
+        }
+
+        if self.static_flag.unwrap_or(false) {
+            cmd.args.push("-static".into());
+        }
+        if self.shared_flag.unwrap_or(false) {
+            cmd.args.push("-shared".into());
         }
 
         if self.cpp {
@@ -721,6 +1114,12 @@ impl Config {
             cmd.args.push(flag.into());
         }
 
+        for flag in self.flags_supported.iter() {
+            if self.is_flag_supported(flag).unwrap_or(false) {
+                cmd.args.push(flag.into());
+            }
+        }
+
         for &(ref key, ref value) in self.definitions.iter() {
             let lead = if let ToolFamily::Msvc = cmd.family {"/"} else {"-"};
             if let Some(ref value) = *value {
@@ -729,11 +1128,22 @@ impl Config {
                 cmd.args.push(format!("{}D{}", lead, key).into());
             }
         }
-        cmd
+
+        if self.warnings {
+            for flag in cmd.family.warnings_flags().iter() {
+                cmd.args.push(flag.into());
+            }
+        }
+
+        if self.warnings_into_errors {
+            cmd.args.push(cmd.family.warnings_to_errors_flag().into());
+        }
+
+        Ok(cmd)
     }
 
-    fn msvc_macro_assembler(&self) -> (Command, String) {
-        let target = self.get_target();
+    fn msvc_macro_assembler(&self) -> Result<(Command, String), Error> {
+        let target = self.get_target()?;
         let tool = if target.contains("x86_64") {
             "ml64.exe"
         } else {
@@ -758,15 +1168,15 @@ impl Config {
             cmd.arg(flag);
         }
 
-        (cmd, tool.to_string())
+        Ok((cmd, tool.to_string()))
     }
 
-    fn assemble(&self, lib_name: &str, dst: &Path, objects: &[PathBuf]) {
+    fn assemble(&self, lib_name: &str, dst: &Path, objects: &[PathBuf]) -> Result<(), Error> {
         // Delete the destination if it exists as the `ar` tool at least on Unix
         // appends to it, which we don't want.
         let _ = fs::remove_file(&dst);
 
-        let target = self.get_target();
+        let target = self.get_target()?;
         if target.contains("msvc") {
             let mut cmd = match self.archiver {
                 Some(ref s) => self.cmd(s),
@@ -778,46 +1188,52 @@ impl Config {
                     .arg("/nologo")
                     .args(objects)
                     .args(&self.objects),
-                "lib.exe");
+                "lib.exe")?;
 
             // The Rust compiler will look for libfoo.a and foo.lib, but the
             // MSVC linker will also be passed foo.lib, so be sure that both
             // exist for now.
             let lib_dst = dst.with_file_name(format!("{}.lib", lib_name));
             let _ = fs::remove_file(&lib_dst);
-            fs::hard_link(&dst, &lib_dst)
+            match fs::hard_link(&dst, &lib_dst)
                 .or_else(|_| {
                     // if hard-link fails, just copy (ignoring the number of bytes written)
                     fs::copy(&dst, &lib_dst).map(|_| ())
-                })
-                .expect("Copying from {:?} to {:?} failed.");;
+                }) {
+                Ok(_) => (),
+                Err(_) => return Err(Error::new(ErrorKind::IOError, "Could not copy or create a hard-link to the generated lib file.")),
+            };
         } else {
-            let ar = self.get_ar();
-            let cmd = ar.file_name().unwrap().to_string_lossy();
+            let ar = self.get_ar()?;
+            let cmd = ar.file_name()
+                .ok_or_else(|| Error::new(ErrorKind::IOError, "Failed to get archiver (ar) path."))?
+                .to_string_lossy();
             run(self.cmd(&ar)
                     .arg("crs")
                     .arg(dst)
                     .args(objects)
                     .args(&self.objects),
-                &cmd);
+                &cmd)?;
         }
+
+        Ok(())
     }
 
-    fn ios_flags(&self, cmd: &mut Tool) {
+    fn ios_flags(&self, cmd: &mut Tool) -> Result<(), Error> {
         enum ArchSpec {
             Device(&'static str),
             Simulator(&'static str),
         }
 
-        let target = self.get_target();
-        let arch = target.split('-').nth(0).unwrap();
+        let target = self.get_target()?;
+        let arch = target.split('-').nth(0).ok_or_else(|| Error::new(ErrorKind::ArchitectureInvalid, "Unknown architecture for iOS target."))?;
         let arch = match arch {
             "arm" | "armv7" | "thumbv7" => ArchSpec::Device("armv7"),
             "armv7s" | "thumbv7s" => ArchSpec::Device("armv7s"),
             "arm64" | "aarch64" => ArchSpec::Device("arm64"),
             "i386" | "i686" => ArchSpec::Simulator("-m32"),
             "x86_64" => ArchSpec::Simulator("-m64"),
-            _ => fail("Unknown arch for iOS target"),
+            _ => return Err(Error::new(ErrorKind::ArchitectureInvalid, "Unknown architecture for iOS target.")),
         };
 
         let sdk = match arch {
@@ -840,14 +1256,18 @@ impl Config {
             .arg("--sdk")
             .arg(sdk)
             .stderr(Stdio::inherit())
-            .output()
-            .unwrap()
+            .output()?
             .stdout;
 
-        let sdk_path = String::from_utf8(sdk_path).unwrap();
+        let sdk_path = match String::from_utf8(sdk_path) {
+            Ok(p) => p,
+            Err(_) => return Err(Error::new(ErrorKind::IOError, "Unable to determine iOS SDK path.")),
+        };
 
         cmd.args.push("-isysroot".into());
         cmd.args.push(sdk_path.trim().into());
+
+        Ok(())
     }
 
     fn cmd<P: AsRef<OsStr>>(&self, prog: P) -> Command {
@@ -858,12 +1278,12 @@ impl Config {
         cmd
     }
 
-    fn get_base_compiler(&self) -> Tool {
+    fn get_base_compiler(&self) -> Result<Tool, Error> {
         if let Some(ref c) = self.compiler {
-            return Tool::new(c.clone());
+            return Ok(Tool::new(c.clone()));
         }
-        let host = self.get_host();
-        let target = self.get_target();
+        let host = self.get_host()?;
+        let target = self.get_target()?;
         let (env, msvc, gnu) = if self.cpp {
             ("CXX", "cl.exe", "g++")
         } else {
@@ -879,7 +1299,7 @@ impl Config {
             "cc"
         };
 
-        self.env_tool(env)
+        let tool_opt: Option<Tool> = self.env_tool(env)
             .map(|(tool, args)| {
                 let mut t = Tool::new(PathBuf::from(tool));
                 for arg in args {
@@ -889,28 +1309,29 @@ impl Config {
             })
             .or_else(|| {
                 if target.contains("emscripten") {
-                    //Windows uses bat file so we have to be a bit more specific
                     let tool = if self.cpp {
-                        if cfg!(windows) {
-                            "em++.bat"
-                        } else {
-                            "em++"
-                        }
+                        "em++"
                     } else {
-                        if cfg!(windows) {
-                            "emcc.bat"
-                        } else {
-                            "emcc"
-                        }
+                        "emcc"
                     };
-
-                    Some(Tool::new(PathBuf::from(tool)))
+                    // Windows uses bat file so we have to be a bit more specific
+                    if cfg!(windows) {
+                        let mut t = Tool::new(PathBuf::from("cmd"));
+                        t.args.push("/c".into());
+                        t.args.push(format!("{}.bat", tool).into());
+                        Some(t)
+                    } else {
+                        Some(Tool::new(PathBuf::from(tool)))
+                    }
                 } else {
                     None
                 }
             })
-            .or_else(|| windows_registry::find_tool(&target, "cl.exe"))
-            .unwrap_or_else(|| {
+            .or_else(|| windows_registry::find_tool(&target, "cl.exe"));
+
+        let tool = match tool_opt {
+            Some(t) => t,
+            None => {
                 let compiler = if host.contains("windows") && target.contains("windows") {
                     if target.contains("msvc") {
                         msvc.to_string()
@@ -919,7 +1340,7 @@ impl Config {
                     }
                 } else if target.contains("android") {
                     format!("{}-{}", target.replace("armv7", "arm"), gnu)
-                } else if self.get_host() != target {
+                } else if self.get_host()? != target {
                     // CROSS_COMPILE is of the form: "arm-linux-gnueabi-"
                     let cc_env = self.getenv("CROSS_COMPILE");
                     let cross_compile = cc_env.as_ref().map(|s| s.trim_right_matches('-'));
@@ -930,14 +1351,14 @@ impl Config {
                         "arm-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
                         "arm-unknown-linux-musleabi" => Some("arm-linux-musleabi"),
                         "arm-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
-                        "arm-unknown-netbsdelf-eabi" => Some("arm--netbsdelf-eabi"),
-                        "armv6-unknown-netbsdelf-eabihf" => Some("armv6--netbsdelf-eabihf"),
+                        "arm-unknown-netbsd-eabi" => Some("arm--netbsdelf-eabi"),
+                        "armv6-unknown-netbsd-eabihf" => Some("armv6--netbsdelf-eabihf"),
                         "armv7-unknown-linux-gnueabihf" => Some("arm-linux-gnueabihf"),
                         "armv7-unknown-linux-musleabihf" => Some("arm-linux-musleabihf"),
-                        "armv7-unknown-netbsdelf-eabihf" => Some("armv7--netbsdelf-eabihf"),
+                        "armv7-unknown-netbsd-eabihf" => Some("armv7--netbsdelf-eabihf"),
                         "i686-pc-windows-gnu" => Some("i686-w64-mingw32"),
                         "i686-unknown-linux-musl" => Some("musl"),
-                        "i686-unknown-netbsdelf" => Some("i486--netbsdelf"),
+                        "i686-unknown-netbsd" => Some("i486--netbsdelf"),
                         "mips-unknown-linux-gnu" => Some("mips-linux-gnu"),
                         "mipsel-unknown-linux-gnu" => Some("mipsel-linux-gnu"),
                         "mips64-unknown-linux-gnuabi64" => Some("mips64-linux-gnuabi64"),
@@ -967,12 +1388,15 @@ impl Config {
                     default.to_string()
                 };
                 Tool::new(PathBuf::from(compiler))
-            })
+            }
+        };
+
+        Ok(tool)
     }
 
-    fn get_var(&self, var_base: &str) -> Result<String, String> {
-        let target = self.get_target();
-        let host = self.get_host();
+    fn get_var(&self, var_base: &str) -> Result<String, Error> {
+        let target = self.get_target()?;
+        let host = self.get_host()?;
         let kind = if host == target { "HOST" } else { "TARGET" };
         let target_u = target.replace("-", "_");
         let res = self.getenv(&format!("{}_{}", var_base, target))
@@ -982,7 +1406,7 @@ impl Config {
 
         match res {
             Some(res) => Ok(res),
-            None => Err("could not get environment variable".to_string()),
+            None => Err(Error::new(ErrorKind::EnvVarNotFound, &format!("Could not find environment variable {}.", var_base))),
         }
     }
 
@@ -997,7 +1421,7 @@ impl Config {
 
     fn env_tool(&self, name: &str) -> Option<(String, Vec<String>)> {
         self.get_var(name).ok().map(|tool| {
-            let whitelist = ["ccache", "distcc"];
+            let whitelist = ["ccache", "distcc", "sccache"];
             for t in whitelist.iter() {
                 if tool.starts_with(t) && tool[t.len()..].starts_with(' ') {
                     return (t.to_string(), vec![tool[t.len()..].trim_left().to_string()]);
@@ -1009,61 +1433,85 @@ impl Config {
 
     /// Returns the default C++ standard library for the current target: `libc++`
     /// for OS X and `libstdc++` for anything else.
-    fn get_cpp_link_stdlib(&self) -> Option<String> {
-        self.cpp_link_stdlib.clone().unwrap_or_else(|| {
-            let target = self.get_target();
-            if target.contains("msvc") {
-                None
-            } else if target.contains("darwin") {
-                Some("c++".to_string())
-            } else if target.contains("freebsd") {
-                Some("c++".to_string())
-            } else {
-                Some("stdc++".to_string())
-            }
-        })
+    fn get_cpp_link_stdlib(&self) -> Result<Option<String>, Error> {
+        match self.cpp_link_stdlib.clone() {
+            Some(s) => Ok(s),
+            None => {
+                let target = self.get_target()?;
+                if target.contains("msvc") {
+                    Ok(None)
+                } else if target.contains("darwin") {
+                    Ok(Some("c++".to_string()))
+                } else if target.contains("freebsd") {
+                    Ok(Some("c++".to_string()))
+                } else {
+                    Ok(Some("stdc++".to_string()))
+                }
+            },
+        }
     }
 
-    fn get_ar(&self) -> PathBuf {
-        self.archiver
+    fn get_ar(&self) -> Result<PathBuf, Error> {
+        match self.archiver
             .clone()
-            .or_else(|| self.get_var("AR").map(PathBuf::from).ok())
-            .unwrap_or_else(|| {
-                if self.get_target().contains("android") {
-                    PathBuf::from(format!("{}-ar", self.get_target().replace("armv7", "arm")))
-                } else if self.get_target().contains("emscripten") {
-                    //Windows use bat files so we have to be a bit more specific
-                    let tool = if cfg!(windows) {
-                        "emar.bat"
-                    } else {
-                        "emar"
-                    };
+            .or_else(|| self.get_var("AR").map(PathBuf::from).ok()) {
+                Some(p) => Ok(p),
+                None => {
+                    if self.get_target()?.contains("android") {
+                        Ok(PathBuf::from(format!("{}-ar", self.get_target()?.replace("armv7", "arm"))))
+                    } else if self.get_target()?.contains("emscripten") {
+                        //Windows use bat files so we have to be a bit more specific
+                        let tool = if cfg!(windows) {
+                            "emar.bat"
+                        } else {
+                            "emar"
+                        };
 
-                    PathBuf::from(tool)
-                } else {
-                    PathBuf::from("ar")
+                        Ok(PathBuf::from(tool))
+                    } else {
+                        Ok(PathBuf::from("ar"))
+                    }
                 }
-            })
+            }
     }
 
-    fn get_target(&self) -> String {
-        self.target.clone().unwrap_or_else(|| self.getenv_unwrap("TARGET"))
+    fn get_target(&self) -> Result<String, Error> {
+        match self.target.clone() {
+            Some(t) => Ok(t),
+            None => Ok(self.getenv_unwrap("TARGET")?),
+        }
     }
 
-    fn get_host(&self) -> String {
-        self.host.clone().unwrap_or_else(|| self.getenv_unwrap("HOST"))
+    fn get_host(&self) -> Result<String, Error> {
+        match self.host.clone() {
+            Some(h) => Ok(h),
+            None => Ok(self.getenv_unwrap("HOST")?),
+        }
     }
 
-    fn get_opt_level(&self) -> String {
-        self.opt_level.as_ref().cloned().unwrap_or_else(|| self.getenv_unwrap("OPT_LEVEL"))
+    fn get_opt_level(&self) -> Result<String, Error> {
+        match self.opt_level.as_ref().cloned() {
+            Some(ol) => Ok(ol),
+            None => Ok(self.getenv_unwrap("OPT_LEVEL")?),
+        }
     }
 
     fn get_debug(&self) -> bool {
-        self.debug.unwrap_or_else(|| self.getenv_unwrap("PROFILE") == "debug")
+        self.debug.unwrap_or_else(|| {
+            match self.getenv("DEBUG") {
+                Some(s) => s != "false",
+                None => false,
+            }
+        })
     }
 
-    fn get_out_dir(&self) -> PathBuf {
-        self.out_dir.clone().unwrap_or_else(|| env::var_os("OUT_DIR").map(PathBuf::from).unwrap())
+    fn get_out_dir(&self) -> Result<PathBuf, Error> {
+        match self.out_dir.clone() {
+            Some(p) => Ok(p),
+            None => Ok(env::var_os("OUT_DIR")
+                .map(PathBuf::from)
+                .ok_or_else(|| Error::new(ErrorKind::EnvVarNotFound, "Environment variable OUT_DIR not defined."))?),
+        }
     }
 
     fn getenv(&self, v: &str) -> Option<String> {
@@ -1072,10 +1520,10 @@ impl Config {
         r
     }
 
-    fn getenv_unwrap(&self, v: &str) -> String {
+    fn getenv_unwrap(&self, v: &str) -> Result<String, Error> {
         match self.getenv(v) {
-            Some(s) => s,
-            None => fail(&format!("environment variable `{}` not defined", v)),
+            Some(s) => Ok(s),
+            None => Err(Error::new(ErrorKind::EnvVarNotFound, &format!("Environment variable {} not defined.", v.to_string()))),
         }
     }
 
@@ -1086,6 +1534,12 @@ impl Config {
     }
 }
 
+impl Default for Build {
+    fn default() -> Build {
+        Build::new()
+    }
+}
+
 impl Tool {
     fn new(path: PathBuf) -> Tool {
         // Try to detect family of the tool from its name, falling back to Gnu.
@@ -1145,31 +1599,42 @@ impl Tool {
     }
 }
 
-fn run(cmd: &mut Command, program: &str) {
-    let (mut child, print) = spawn(cmd, program);
-    let status = child.wait().expect("failed to wait on child process");
+fn run(cmd: &mut Command, program: &str) -> Result<(), Error> {
+    let (mut child, print) = spawn(cmd, program)?;
+    let status = match child.wait() {
+        Ok(s) => s,
+        Err(_) => return Err(Error::new(ErrorKind::ToolExecError, &format!("Failed to wait on spawned child process, command {:?} with args {:?}.", cmd, program))),
+    };
     print.join().unwrap();
     println!("{}", status);
-    if !status.success() {
-        fail(&format!("command did not execute successfully, got: {}", status));
+
+    if status.success() {
+        Ok(())
+    } else {
+        Err(Error::new(ErrorKind::ToolExecError, &format!("Command {:?} with args {:?} did not execute successfully (status code {}).", cmd, program, status)))
     }
 }
 
-fn run_output(cmd: &mut Command, program: &str) -> Vec<u8> {
+fn run_output(cmd: &mut Command, program: &str) -> Result<Vec<u8>, Error> {
     cmd.stdout(Stdio::piped());
-    let (mut child, print) = spawn(cmd, program);
+    let (mut child, print) = spawn(cmd, program)?;
     let mut stdout = vec![];
     child.stdout.take().unwrap().read_to_end(&mut stdout).unwrap();
-    let status = child.wait().expect("failed to wait on child process");
+    let status = match child.wait() {
+        Ok(s) => s,
+        Err(_) => return Err(Error::new(ErrorKind::ToolExecError, &format!("Failed to wait on spawned child process, command {:?} with args {:?}.", cmd, program))),
+    };
     print.join().unwrap();
     println!("{}", status);
-    if !status.success() {
-        fail(&format!("command did not execute successfully, got: {}", status));
+
+    if status.success() {
+        Ok(stdout)
+    } else {
+        Err(Error::new(ErrorKind::ToolExecError, &format!("Command {:?} with args {:?} did not execute successfully (status code {}).", cmd, program, status)))
     }
-    stdout
 }
 
-fn spawn(cmd: &mut Command, program: &str) -> (Child, JoinHandle<()>) {
+fn spawn(cmd: &mut Command, program: &str) -> Result<(Child, JoinHandle<()>), Error> {
     println!("running: {:?}", cmd);
 
     // Capture the standard error coming from these programs, and write it out
@@ -1186,7 +1651,7 @@ fn spawn(cmd: &mut Command, program: &str) -> (Child, JoinHandle<()>) {
                     println!("");
                 }
             });
-            (child, print)
+            Ok((child, print))
         }
         Err(ref e) if e.kind() == io::ErrorKind::NotFound => {
             let extra = if cfg!(windows) {
@@ -1195,17 +1660,25 @@ fn spawn(cmd: &mut Command, program: &str) -> (Child, JoinHandle<()>) {
             } else {
                 ""
             };
-            fail(&format!("failed to execute command: {}\nIs `{}` \
-                           not installed?{}",
-                          e,
-                          program,
-                          extra));
+            Err(Error::new(ErrorKind::ToolNotFound, &format!("Failed to find tool. Is `{}` installed?{}", program, extra)))
         }
-        Err(e) => fail(&format!("failed to execute command: {}", e)),
+        Err(_) => Err(Error::new(ErrorKind::ToolExecError, &format!("Command {:?} with args {:?} failed to start.", cmd, program))),
     }
 }
 
 fn fail(s: &str) -> ! {
-    println!("\n\n{}\n\n", s);
-    panic!()
+    panic!("\n\nInternal error occurred: {}\n\n", s)
+}
+
+
+fn command_add_output_file(cmd: &mut Command, dst: &Path, msvc: bool, is_asm: bool) {
+    if msvc && is_asm {
+        cmd.arg("/Fo").arg(dst);
+    } else if msvc {
+        let mut s = OsString::from("/Fo");
+        s.push(&dst);
+        cmd.arg(s);
+    } else {
+        cmd.arg("-o").arg(&dst);
+    }
 }