introduce operating system version ranges as part of the target

 * re-introduce `std.build.Target` which is distinct from `std.Target`.
   `std.build.Target` wraps `std.Target` so that it can be annotated as
   "the native target" or an explicitly specified target.
 * `std.Target.Os` is moved to `std.Target.Os.Tag`. The former is now a
   struct which has the tag as well as version range information.
 * `std.elf` gains some more ELF header constants.
 * `std.Target.parse` gains the ability to parse operating system
   version ranges as well as glibc version.
 * Added `std.Target.isGnuLibC()`.
 * self-hosted dynamic linker detection and glibc version detection.
   This also adds the improved logic using `/usr/bin/env` rather than
   invoking the system C compiler to find the dynamic linker when zig
   is statically linked. Related: #2084
   Note: this `/usr/bin/env` code is work-in-progress.
 * `-target-glibc` CLI option is removed in favor of the new `-target`
   syntax. Example: `-target x86_64-linux-gnu.2.27`

closes #1907

1 files changed, 7 insertions, 6 deletions

diff --git a/lib/std/special/compiler_rt.zig b/lib/std/special/compiler_rt.zig
index 8d49fdbd2a..3126e81b9d 100644
--- a/lib/std/special/compiler_rt.zig
+++ b/lib/std/special/compiler_rt.zig
@@ -1,11 +1,12 @@
-const builtin = @import("builtin");
+const std = @import("std");
+const builtin = std.builtin;
 const is_test = builtin.is_test;
 
 const is_gnu = switch (builtin.abi) {
     .gnu, .gnuabin32, .gnuabi64, .gnueabi, .gnueabihf, .gnux32 => true,
     else => false,
 };
-const is_mingw = builtin.os == .windows and is_gnu;
+const is_mingw = builtin.os.tag == .windows and is_gnu;
 
 comptime {
     const linkage = if (is_test) builtin.GlobalLinkage.Internal else builtin.GlobalLinkage.Weak;
@@ -180,7 +181,7 @@ comptime {
         @export(@import("compiler_rt/arm.zig").__aeabi_memclr, .{ .name = "__aeabi_memclr4", .linkage = linkage });
         @export(@import("compiler_rt/arm.zig").__aeabi_memclr, .{ .name = "__aeabi_memclr8", .linkage = linkage });
 
-        if (builtin.os == .linux) {
+        if (builtin.os.tag == .linux) {
             @export(@import("compiler_rt/arm.zig").__aeabi_read_tp, .{ .name = "__aeabi_read_tp", .linkage = linkage });
         }
 
@@ -250,7 +251,7 @@ comptime {
         @export(@import("compiler_rt/aullrem.zig")._aullrem, .{ .name = "\x01__aullrem", .linkage = strong_linkage });
     }
 
-    if (builtin.os == .windows) {
+    if (builtin.os.tag == .windows) {
         // Default stack-probe functions emitted by LLVM
         if (is_mingw) {
             @export(@import("compiler_rt/stack_probe.zig")._chkstk, .{ .name = "_alloca", .linkage = strong_linkage });
@@ -288,7 +289,7 @@ comptime {
             else => {},
         }
     } else {
-        if (builtin.glibc_version != null) {
+        if (std.Target.current.isGnuLibC()) {
             @export(__stack_chk_guard, .{ .name = "__stack_chk_guard", .linkage = linkage });
         }
         @export(@import("compiler_rt/divti3.zig").__divti3, .{ .name = "__divti3", .linkage = linkage });
@@ -307,7 +308,7 @@ comptime {
 pub fn panic(msg: []const u8, error_return_trace: ?*builtin.StackTrace) noreturn {
     @setCold(true);
     if (is_test) {
-        @import("std").debug.panic("{}", .{msg});
+        std.debug.panic("{}", .{msg});
     } else {
         unreachable;
     }