From 47876e637185e2194dde1b9245e1bc603a604d7e Mon Sep 17 00:00:00 2001
From: Manlio Perillo <manlio.perillo@gmail.com>
Date: Mon, 10 Apr 2023 21:24:49 +0200
Subject: [PATCH] build: make PrintStep thread safe

Update PrintStep to always printing to stderr, using std.debug.print, so
that the message is written atomically.

Note that currently it is not an issue, since PrintStep prints the
message before everything else.
---
 build.zig | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/build.zig b/build.zig
index 8b93e2b..84535d1 100644
--- a/build.zig
+++ b/build.zig
@@ -557,7 +557,7 @@ pub fn build(b: *Build) !void {
     const use_healed = b.option(bool, "healed", "Run exercises from patches/healed") orelse false;
     const exno: ?usize = b.option(usize, "n", "Select exercise");
 
-    const header_step = PrintStep.create(b, logo, std.io.getStdErr());
+    const header_step = PrintStep.create(b, logo);
 
     if (exno) |n| {
         if (n == 0 or n > exercises.len - 1) {
@@ -861,13 +861,12 @@ const ZiglingStep = struct {
     }
 };
 
-// Print a message to a file.
+// Print a message to stderr.
 const PrintStep = struct {
     step: Step,
     message: []const u8,
-    file: std.fs.File,
 
-    pub fn create(owner: *Build, message: []const u8, file: std.fs.File) *PrintStep {
+    pub fn create(owner: *Build, message: []const u8) *PrintStep {
         const self = owner.allocator.create(PrintStep) catch @panic("OOM");
         self.* = .{
             .step = Step.init(.{
@@ -877,7 +876,6 @@ const PrintStep = struct {
                 .makeFn = make,
             }),
             .message = message,
-            .file = file,
         };
 
         return self;
@@ -887,7 +885,7 @@ const PrintStep = struct {
         _ = prog_node;
         const p = @fieldParentPtr(PrintStep, "step", step);
 
-        try p.file.writeAll(p.message);
+        print("{s}", .{p.message});
     }
 };