proof of concept build system

see #204

std/build.zig

@@ -57,9 +57,8 @@ pub const Builder = struct {
             %return zig_args.append(exe.name);
 
             printInvocation(self.zig_exe, zig_args);
-            const TODO_env: []const []const u8 = undefined; // TODO
-            var child = %return os.ChildProcess.spawn(self.zig_exe, zig_args.toSliceConst(), TODO_env,
-                StdIo.Ignore, StdIo.Inherit, StdIo.Inherit);
+            var child = %return os.ChildProcess.spawn(self.zig_exe, zig_args.toSliceConst(), os.environ,
+                StdIo.Ignore, StdIo.Inherit, StdIo.Inherit, self.allocator);
             const term = %return child.wait();
             switch (term) {
                 Term.Clean => |code| {

std/os/index.zig

@@ -83,7 +83,7 @@ pub coldcc fn abort() -> noreturn {
         c.abort();
     }
     switch (@compileVar("os")) {
-        Os.linux => {
+        Os.linux, Os.darwin, Os.macosx, Os.ios => {
             _ = posix.raise(posix.SIGABRT);
             _ = posix.raise(posix.SIGKILL);
             while (true) {}
@@ -234,12 +234,12 @@ pub const ChildProcess = struct {
         Close,
     };
 
-    pub fn spawn(exe_path: []const u8, args: []const []const u8, env: []const []const u8,
-        stdin: StdIo, stdout: StdIo, stderr: StdIo) -> %ChildProcess
+    pub fn spawn(exe_path: []const u8, args: []const []const u8, env: []const EnvPair,
+        stdin: StdIo, stdout: StdIo, stderr: StdIo, allocator: &Allocator) -> %ChildProcess
     {
         switch (@compileVar("os")) {
             Os.linux, Os.macosx, Os.ios, Os.darwin => {
-                return spawnPosix(exe_path, args, env, stdin, stdout, stderr);
+                return spawnPosix(exe_path, args, env, stdin, stdout, stderr, allocator);
             },
             else => @compileError("Unsupported OS"),
         }
@@ -301,8 +301,8 @@ pub const ChildProcess = struct {
         };
     }
 
-    fn spawnPosix(exe_path: []const u8, args: []const []const u8, env: []const []const u8,
-        stdin: StdIo, stdout: StdIo, stderr: StdIo) -> %ChildProcess
+    fn spawnPosix(exe_path: []const u8, args: []const []const u8, env: []const EnvPair,
+        stdin: StdIo, stdout: StdIo, stderr: StdIo, allocator: &Allocator) -> %ChildProcess
     {
         // TODO issue #295
         //const stdin_pipe = if (stdin == StdIo.Pipe) %return makePipe() else undefined;
@@ -358,7 +358,7 @@ pub const ChildProcess = struct {
             setUpChildIo(stderr, stderr_pipe[1], posix.STDERR_FILENO, dev_null_fd) %%
                 |err| forkChildErrReport(err_pipe[1], err);
 
-            const err = posix.getErrno(posix.execve(exe_path, args, env));
+            const err = posix.getErrno(%return execve(exe_path, args, env, allocator));
             assert(err > 0);
             forkChildErrReport(err_pipe[1], switch (err) {
                 errno.EFAULT => unreachable,
@@ -419,6 +419,65 @@ pub const ChildProcess = struct {
     }
 };
 
+/// This function must allocate memory to add a null terminating bytes on path and each arg.
+/// It must also convert to KEY=VALUE\0 format for environment variables, and include null
+/// pointers after the args and after the environment variables.
+/// Also make the first arg equal to path.
+fn execve(path: []const u8, argv: []const []const u8, envp: []const EnvPair, allocator: &Allocator) -> %usize {
+    const path_buf = %return allocator.alloc(u8, path.len + 1);
+    defer allocator.free(path_buf);
+    @memcpy(&path_buf[0], &path[0], path.len);
+    path_buf[path.len] = 0;
+
+    const argv_buf = %return allocator.alloc(?&const u8, argv.len + 2);
+    mem.set(?&const u8, argv_buf, null);
+    defer {
+        for (argv_buf) |arg, i| {
+            const arg_buf = if (const ptr ?= arg) ptr[0...argv[i].len + 1] else break;
+            allocator.free(arg_buf);
+        }
+        allocator.free(argv_buf);
+    }
+    {
+        // Add path to the first argument.
+        const arg_buf = %return allocator.alloc(u8, path.len + 1);
+        @memcpy(&arg_buf[0], path.ptr, path.len);
+        arg_buf[path.len] = 0;
+
+        argv_buf[0] = arg_buf.ptr;
+    }
+    for (argv) |arg, i| {
+        const arg_buf = %return allocator.alloc(u8, arg.len + 1);
+        @memcpy(&arg_buf[0], arg.ptr, arg.len);
+        arg_buf[arg.len] = 0;
+
+        argv_buf[i + 1] = arg_buf.ptr;
+    }
+    argv_buf[argv.len + 1] = null;
+
+    const envp_buf = %return allocator.alloc(?&const u8, envp.len + 1);
+    mem.set(?&const u8, envp_buf, null);
+    defer {
+        for (envp_buf) |env, i| {
+            const env_buf = if (const ptr ?= env) ptr[0...envp[i].key.len + envp[i].value.len + 2] else break;
+            allocator.free(env_buf);
+        }
+        allocator.free(envp_buf);
+    }
+    for (envp) |pair, i| {
+        const env_buf = %return allocator.alloc(u8, pair.key.len + pair.value.len + 2);
+        @memcpy(&env_buf[0], pair.key.ptr, pair.key.len);
+        env_buf[pair.key.len] = '=';
+        @memcpy(&env_buf[pair.key.len + 1], pair.value.ptr, pair.value.len);
+        env_buf[env_buf.len - 1] = 0;
+
+        envp_buf[i] = env_buf.ptr;
+    }
+    envp_buf[envp.len] = null;
+
+    return posix.execve(path_buf.ptr, argv_buf.ptr, envp_buf.ptr);
+}
+
 pub const EnvPair = struct {
     key: []const u8,
     value: []const u8,

std/os/linux.zig

@@ -261,40 +261,8 @@ pub fn dup2(old: i32, new: i32) -> usize {
     arch.syscall2(arch.SYS_dup2, usize(old), usize(new))
 }
 
-pub fn execve_c(path: &const u8, argv: &const ?&const u8, envp: &const ?&const u8) -> usize {
-    arch.syscall3(arch.SYS_execve, path, argv, envp)
-}
-
-/// This function must allocate memory to add a null terminating bytes on path, each arg,
-/// and each environment variable line, as well as a null pointer after the arg list and
-/// environment variable list. We allocate stack memory since the process is about to get
-/// wiped anyway.
-pub fn execve(path: []const u8, argv: []const []const u8, envp: []const []const u8) -> usize {
-    const path_buf = @alloca(u8, path.len + 1);
-    @memcpy(&path_buf[0], &path[0], path.len);
-    path_buf[path.len] = 0;
-
-    const argv_buf = @alloca([]const ?&const u8, argv.len + 1);
-    for (argv) |arg, i| {
-        const arg_buf = @alloca(u8, arg.len + 1);
-        @memcpy(&arg_buf[0], &arg[0], arg.len);
-        arg_buf[arg.len] = 0;
-
-        argv[i] = arg_buf;
-    }
-    argv_buf[argv.len] = null;
-
-    const envp_buf = @alloca([]const ?&const u8, envp.len + 1);
-    for (envp) |env, i| {
-        const env_buf = @alloca(u8, env.len + 1);
-        @memcpy(&env_buf[0], &env[0], env.len);
-        env_buf[env.len] = 0;
-
-        envp[i] = env_buf;
-    }
-    envp_buf[envp.len] = null;
-
-    return execve_c(path_buf.ptr, argv_buf.ptr, envp_buf.ptr);
+pub fn execve(path: &const u8, argv: &const ?&const u8, envp: &const ?&const u8) -> usize {
+    arch.syscall3(arch.SYS_execve, usize(path), usize(argv), usize(envp))
 }
 
 pub fn fork() -> usize {

std/special/build_runner.zig

@@ -4,7 +4,13 @@ const io = std.io;
 const Builder = std.build.Builder;
 const mem = std.mem;
 
+error InvalidArgs;
+
 pub fn main(args: [][]u8) -> %void {
+    if (args.len < 2) {
+        %%io.stderr.printf("Expected first argument to be path to zig compiler\n");
+        return error.InvalidArgs;
+    }
     const zig_exe = args[1];
     const leftover_args = args[2...];