stage2 MachO: add source version load cmd

lib/std/macho.zig

@@ -722,6 +722,19 @@ pub const version_min_command = extern struct {
     sdk: u32,
 };
 
+/// The source_version_command is an optional load command containing
+/// the version of the sources used to build the binary.
+pub const source_version_command = extern struct {
+    /// LC_SOURCE_VERSION
+    cmd: u32,
+
+    /// sizeof(source_version_command)
+    cmdsize: u32,
+
+    /// A.B.C.D.E packed as a24.b10.c10.d10.e10
+    version: u64,
+};
+
 /// After MacOS X 10.1 when a new load command is added that is required to be
 /// understood by the dynamic linker for the image to execute properly the
 /// LC_REQ_DYLD bit will be or'ed into the load command constant.  If the dynamic

src/link/MachO.zig

@@ -34,6 +34,7 @@ const LoadCommand = union(enum) {
     Dylib: macho.dylib_command,
     EntryPoint: macho.entry_point_command,
     MinVersion: macho.version_min_command,
+    SourceVersion: macho.source_version_command,
 
     pub fn cmdsize(self: LoadCommand) u32 {
         return switch (self) {
@@ -46,6 +47,7 @@ const LoadCommand = union(enum) {
             .Dylib => |x| x.cmdsize,
             .EntryPoint => |x| x.cmdsize,
             .MinVersion => |x| x.cmdsize,
+            .SourceVersion => |x| x.cmdsize,
         };
     }
 
@@ -60,6 +62,7 @@ const LoadCommand = union(enum) {
             .Dylib => |cmd| writeGeneric(cmd, file, offset),
             .EntryPoint => |cmd| writeGeneric(cmd, file, offset),
             .MinVersion => |cmd| writeGeneric(cmd, file, offset),
+            .SourceVersion => |cmd| writeGeneric(cmd, file, offset),
         };
     }
 
@@ -101,6 +104,8 @@ function_starts_cmd_index: ?u16 = null,
 main_cmd_index: ?u16 = null,
 /// Minimum OS version
 version_min_cmd_index: ?u16 = null,
+/// Source version
+source_version_cmd_index: ?u16 = null,
 
 /// Table of all sections
 sections: std.ArrayListUnmanaged(macho.section_64) = .{},
@@ -1377,6 +1382,16 @@ pub fn populateMissingMetadata(self: *MachO) !void {
             },
         });
     }
+    if (self.source_version_cmd_index == null) {
+        self.source_version_cmd_index = @intCast(u16, self.load_commands.items.len);
+        try self.load_commands.append(self.base.allocator, .{
+            .SourceVersion = .{
+                .cmd = macho.LC_SOURCE_VERSION,
+                .cmdsize = @sizeOf(macho.source_version_command),
+                .version = 0x0,
+            },
+        });
+    }
     {
         const linkedit = &self.load_commands.items[self.linkedit_segment_cmd_index.?].Segment;
         const dyld_info = &self.load_commands.items[self.dyld_info_cmd_index.?].DyldInfo;