From 410b4d9bdf8abb8dad2ac2e11038fe492b8be869 Mon Sep 17 00:00:00 2001
From: Josh Wolfe <thejoshwolfe@gmail.com>
Date: Sun, 8 Jul 2018 00:00:05 -0400
Subject: [PATCH] builder.addBuildOption

---
 std/build.zig | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/std/build.zig b/std/build.zig
index 99de9b519..24fa85383 100644
--- a/std/build.zig
+++ b/std/build.zig
@@ -814,6 +814,7 @@ pub const LibExeObjStep = struct {
     out_h_filename: []const u8,
     assembly_files: ArrayList([]const u8),
     packages: ArrayList(Pkg),
+    build_options_contents: std.Buffer,
 
     // C only stuff
     source_files: ArrayList([]const u8),
@@ -905,6 +906,7 @@ pub const LibExeObjStep = struct {
             .lib_paths = ArrayList([]const u8).init(builder.allocator),
             .object_src = undefined,
             .disable_libc = true,
+            .build_options_contents = std.Buffer.initSize(builder.allocator, 0) catch unreachable,
         };
         self.computeOutFileNames();
         return self;
@@ -945,6 +947,7 @@ pub const LibExeObjStep = struct {
             .out_h_filename = undefined,
             .assembly_files = undefined,
             .packages = undefined,
+            .build_options_contents = undefined,
         };
         self.computeOutFileNames();
         return self;
@@ -1096,6 +1099,12 @@ pub const LibExeObjStep = struct {
         self.include_dirs.append(self.builder.cache_root) catch unreachable;
     }
 
+    pub fn addBuildOption(self: *LibExeObjStep, comptime T: type, name: []const u8, value: T) void {
+        assert(self.is_zig);
+        const out = &std.io.BufferOutStream.init(&self.build_options_contents).stream;
+        out.print("pub const {} = {};\n", name, value) catch unreachable;
+    }
+
     pub fn addIncludeDir(self: *LibExeObjStep, path: []const u8) void {
         self.include_dirs.append(path) catch unreachable;
     }
@@ -1155,6 +1164,15 @@ pub const LibExeObjStep = struct {
             zig_args.append(builder.pathFromRoot(root_src)) catch unreachable;
         }
 
+        if (self.build_options_contents.len() > 0) {
+            const build_options_file = try os.path.join(builder.allocator, builder.cache_root, builder.fmt("{}_build_options.zig", self.name));
+            try std.io.writeFile(builder.allocator, build_options_file, self.build_options_contents.toSliceConst());
+            try zig_args.append("--pkg-begin");
+            try zig_args.append("build_options");
+            try zig_args.append(builder.pathFromRoot(build_options_file));
+            try zig_args.append("--pkg-end");
+        }
+
         for (self.object_files.toSliceConst()) |object_file| {
             zig_args.append("--object") catch unreachable;
             zig_args.append(builder.pathFromRoot(object_file)) catch unreachable;