stage2: add support for -fbuild-id,-fno-build-id

closes #3047

Author: andrewrk

build.zig

@@ -145,6 +145,7 @@ pub fn build(b: *Builder) !void {
 
     const exe = b.addExecutable("zig", main_file);
     exe.strip = strip;
+    exe.build_id = !strip;
     exe.install();
     exe.setBuildMode(mode);
     exe.setTarget(target);

lib/std/build.zig

@@ -1549,6 +1549,12 @@ pub const LibExeObjStep = struct {
 
     valgrind_support: ?bool = null,
     each_lib_rpath: ?bool = null,
+    /// On ELF targets, this will emit a link section called ".note.gnu.build-id"
+    /// which can be used to coordinate a stripped binary with its debug symbols.
+    /// As an example, the bloaty project refuses to work unless its inputs have
+    /// build ids, in order to prevent accidental mismatches.
+    /// The default is to not include this section because it slows down linking.
+    build_id: ?bool = null,
 
     /// Create a .eh_frame_hdr section and a PT_GNU_EH_FRAME segment in the ELF
     /// file.
@@ -2953,6 +2959,14 @@ pub const LibExeObjStep = struct {
             }
         }
 
+        if (self.build_id) |build_id| {
+            if (build_id) {
+                try zig_args.append("-fbuild-id");
+            } else {
+                try zig_args.append("-fno-build-id");
+            }
+        }
+
         if (self.override_lib_dir) |dir| {
             try zig_args.append("--zig-lib-dir");
             try zig_args.append(builder.pathFromRoot(dir));

src/Compilation.zig

@@ -757,6 +757,7 @@ pub const InitOptions = struct {
     linker_global_base: ?u64 = null,
     linker_export_symbol_names: []const []const u8 = &.{},
     each_lib_rpath: ?bool = null,
+    build_id: ?bool = null,
     disable_c_depfile: bool = false,
     linker_z_nodelete: bool = false,
     linker_z_notext: bool = false,
@@ -1640,6 +1641,7 @@ pub fn create(gpa: Allocator, options: InitOptions) !*Compilation {
             .skip_linker_dependencies = options.skip_linker_dependencies,
             .parent_compilation_link_libc = options.parent_compilation_link_libc,
             .each_lib_rpath = options.each_lib_rpath orelse options.is_native_os,
+            .build_id = options.build_id orelse false,
             .cache_mode = cache_mode,
             .disable_lld_caching = options.disable_lld_caching or cache_mode == .whole,
             .subsystem = options.subsystem,
@@ -2340,6 +2342,7 @@ fn addNonIncrementalStuffToCacheManifest(comp: *Compilation, man: *Cache.Manifes
     man.hash.addListOfBytes(comp.bin_file.options.lib_dirs);
     man.hash.addListOfBytes(comp.bin_file.options.rpath_list);
     man.hash.add(comp.bin_file.options.each_lib_rpath);
+    man.hash.add(comp.bin_file.options.build_id);
     man.hash.add(comp.bin_file.options.skip_linker_dependencies);
     man.hash.add(comp.bin_file.options.z_nodelete);
     man.hash.add(comp.bin_file.options.z_notext);

src/link.zig

@@ -146,6 +146,7 @@ pub const Options = struct {
     skip_linker_dependencies: bool,
     parent_compilation_link_libc: bool,
     each_lib_rpath: bool,
+    build_id: bool,
     disable_lld_caching: bool,
     is_test: bool,
     use_stage1: bool,

src/link/Elf.zig

@@ -1311,7 +1311,6 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
         // We can skip hashing libc and libc++ components that we are in charge of building from Zig
         // installation sources because they are always a product of the compiler version + target information.
         man.hash.addOptionalBytes(self.base.options.entry);
-        man.hash.add(stack_size);
         man.hash.addOptional(self.base.options.image_base_override);
         man.hash.add(gc_sections);
         man.hash.add(self.base.options.eh_frame_hdr);
@@ -1320,6 +1319,10 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
         man.hash.addListOfBytes(self.base.options.lib_dirs);
         man.hash.addListOfBytes(self.base.options.rpath_list);
         man.hash.add(self.base.options.each_lib_rpath);
+        if (self.base.options.output_mode == .Exe) {
+            man.hash.add(stack_size);
+            man.hash.add(self.base.options.build_id);
+        }
         man.hash.add(self.base.options.skip_linker_dependencies);
         man.hash.add(self.base.options.z_nodelete);
         man.hash.add(self.base.options.z_notext);
@@ -1450,6 +1453,10 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
         if (self.base.options.output_mode == .Exe) {
             try argv.append("-z");
             try argv.append(try std.fmt.allocPrint(arena, "stack-size={d}", .{stack_size}));
+
+            if (self.base.options.build_id) {
+                try argv.append("--build-id");
+            }
         }
 
         if (self.base.options.image_base_override) |image_base| {

src/main.zig

@@ -423,6 +423,8 @@ const usage_build_generic =
     \\  -fno-each-lib-rpath            Prevent adding rpath for each used dynamic library
     \\  -fallow-shlib-undefined        Allows undefined symbols in shared libraries
     \\  -fno-allow-shlib-undefined     Disallows undefined symbols in shared libraries
+    \\  -fbuild-id                     Helps coordinate stripped binaries with debug symbols
+    \\  -fno-build-id                  (default) Saves a bit of time linking
     \\  --eh-frame-hdr                 Enable C++ exception handling by passing --eh-frame-hdr to linker
     \\  --emit-relocs                  Enable output of relocation sections for post build tools
     \\  -z [arg]                       Set linker extension flags
@@ -671,6 +673,7 @@ fn buildOutputType(
     var link_eh_frame_hdr = false;
     var link_emit_relocs = false;
     var each_lib_rpath: ?bool = null;
+    var build_id: ?bool = null;
     var sysroot: ?[]const u8 = null;
     var libc_paths_file: ?[]const u8 = try optionalStringEnvVar(arena, "ZIG_LIBC");
     var machine_code_model: std.builtin.CodeModel = .default;
@@ -1030,6 +1033,10 @@ fn buildOutputType(
                         each_lib_rpath = true;
                     } else if (mem.eql(u8, arg, "-fno-each-lib-rpath")) {
                         each_lib_rpath = false;
+                    } else if (mem.eql(u8, arg, "-fbuild-id")) {
+                        build_id = true;
+                    } else if (mem.eql(u8, arg, "-fno-build-id")) {
+                        build_id = false;
                     } else if (mem.eql(u8, arg, "--enable-cache")) {
                         enable_cache = true;
                     } else if (mem.eql(u8, arg, "--test-cmd-bin")) {
@@ -1415,10 +1422,20 @@ fn buildOutputType(
                         while (split_it.next()) |linker_arg| {
                             // Handle nested-joined args like `-Wl,-rpath=foo`.
                             // Must be prefixed with 1 or 2 dashes.
-                            if (linker_arg.len >= 3 and linker_arg[0] == '-' and linker_arg[2] != '-') {
+                            if (linker_arg.len >= 3 and
+                                linker_arg[0] == '-' and
+                                linker_arg[2] != '-')
+                            {
                                 if (mem.indexOfScalar(u8, linker_arg, '=')) |equals_pos| {
-                                    try linker_args.append(linker_arg[0..equals_pos]);
-                                    try linker_args.append(linker_arg[equals_pos + 1 ..]);
+                                    const key = linker_arg[0..equals_pos];
+                                    const value = linker_arg[equals_pos + 1 ..];
+                                    if (mem.eql(u8, key, "build-id")) {
+                                        build_id = true;
+                                        warn("ignoring build-id style argument: '{s}'", .{value});
+                                        continue;
+                                    }
+                                    try linker_args.append(key);
+                                    try linker_args.append(value);
                                     continue;
                                 }
                             }
@@ -2727,6 +2744,7 @@ fn buildOutputType(
         .stack_report = stack_report,
         .is_test = arg_mode == .zig_test,
         .each_lib_rpath = each_lib_rpath,
+        .build_id = build_id,
         .test_evented_io = test_evented_io,
         .test_filter = test_filter,
         .test_name_prefix = test_name_prefix,