zig/std/special/bootstrap.zig
Andrew Kelley 21767144fc linux: support VDSO for clock_gettime
also fix a compiler crash when using cmpxchg with nullable pointer
2018-04-22 18:11:50 -04:00

110 lines
3.6 KiB
Zig

// This file is in a package which has the root source file exposed as "@root".
// It is included in the compilation unit when exporting an executable.
const root = @import("@root");
const std = @import("std");
const builtin = @import("builtin");
var argc_ptr: &usize = undefined;
comptime {
const strong_linkage = builtin.GlobalLinkage.Strong;
if (builtin.link_libc) {
@export("main", main, strong_linkage);
} else if (builtin.os == builtin.Os.windows) {
@export("WinMainCRTStartup", WinMainCRTStartup, strong_linkage);
} else if (builtin.os == builtin.Os.zen) {
@export("_start", zen_start, strong_linkage);
} else {
@export("_start", _start, strong_linkage);
}
}
extern fn zen_start() noreturn {
std.os.posix.exit(@inlineCall(callMain));
}
nakedcc fn _start() noreturn {
switch (builtin.arch) {
builtin.Arch.x86_64 => {
argc_ptr = asm("lea (%%rsp), %[argc]": [argc] "=r" (-> &usize));
},
builtin.Arch.i386 => {
argc_ptr = asm("lea (%%esp), %[argc]": [argc] "=r" (-> &usize));
},
else => @compileError("unsupported arch"),
}
// If LLVM inlines stack variables into _start, they will overwrite
// the command line argument data.
@noInlineCall(posixCallMainAndExit);
}
extern fn WinMainCRTStartup() noreturn {
@setAlignStack(16);
std.os.windows.ExitProcess(callMain());
}
fn posixCallMainAndExit() noreturn {
const argc = *argc_ptr;
const argv = @ptrCast(&&u8, &argc_ptr[1]);
const envp_nullable = @ptrCast(&?&u8, &argv[argc + 1]);
var envp_count: usize = 0;
while (envp_nullable[envp_count]) |_| : (envp_count += 1) {}
const envp = @ptrCast(&&u8, envp_nullable)[0..envp_count];
if (builtin.os == builtin.Os.linux) {
const auxv = &@ptrCast(&usize, envp.ptr)[envp_count + 1];
var i: usize = 0;
while (auxv[i] != 0) : (i += 2) {
if (auxv[i] < std.os.linux_aux_raw.len) std.os.linux_aux_raw[auxv[i]] = auxv[i+1];
}
std.debug.assert(std.os.linux_aux_raw[std.elf.AT_PAGESZ] == std.os.page_size);
}
std.os.posix.exit(callMainWithArgs(argc, argv, envp));
}
fn callMainWithArgs(argc: usize, argv: &&u8, envp: []&u8) u8 {
std.os.ArgIteratorPosix.raw = argv[0..argc];
std.os.posix_environ_raw = envp;
return callMain();
}
extern fn main(c_argc: i32, c_argv: &&u8, c_envp: &?&u8) i32 {
var env_count: usize = 0;
while (c_envp[env_count] != null) : (env_count += 1) {}
const envp = @ptrCast(&&u8, c_envp)[0..env_count];
return callMainWithArgs(usize(c_argc), c_argv, envp);
}
fn callMain() u8 {
switch (@typeId(@typeOf(root.main).ReturnType)) {
builtin.TypeId.NoReturn => {
root.main();
},
builtin.TypeId.Void => {
root.main();
return 0;
},
builtin.TypeId.Int => {
if (@typeOf(root.main).ReturnType.bit_count != 8) {
@compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'");
}
return root.main();
},
builtin.TypeId.ErrorUnion => {
root.main() catch |err| {
std.debug.warn("error: {}\n", @errorName(err));
if (builtin.os != builtin.Os.zen) {
if (@errorReturnTrace()) |trace| {
std.debug.dumpStackTrace(trace);
}
}
return 1;
};
return 0;
},
else => @compileError("expected return type of main to be 'u8', 'noreturn', 'void', or '!void'"),
}
}