Commit 6b2709616e22e7651f16293034cc0d25f0e9be0a | zig

author	Andrew Kelley <andrew@ziglang.org> 2023-12-29 16:51:20-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2024-01-01 19:49:08-07:00
log	6b2709616e22e7651f16293034cc0d25f0e9be0a
tree	d3dc659be126b3e6212197c955c52fbe277894a9
parent	a89d6878d2780f966b7327f8d366e6ac5f5cd8fc

frontend: ignore AccessDenied when writing builtin.zig

This issue already existed in master branch, however, the more
aggressive caching of builtin.zig in this branch made it happen more
often. I added doc comments to AtomicFile to explain when this problem
can occur.

For the compiler's use case, error.AccessDenied can be simply swallowed
because it means the destination file already exists and there is
nothing else to do besides proceed with the AtomicFile cleanup.

I never solved the mystery of why the log statements weren't printing
but those are temporary debugging instruments anyway, and I am already
too many yaks deep to whip out another razor.

closes #14978

2 files changed, 17 insertions(+), 17 deletions(-)

lib
- std
  - fs
    AtomicFile.zig
src
- Builtin.zig

lib/std/fs/AtomicFile.zig+4

 @@ -65,6 +65,10 @@ pub fn deinit(self: *AtomicFile) void {
 pub const FinishError = posix.RenameError;
+/// On Windows, this function introduces a period of time where some file
+/// system operations on the destination file will result in
+/// `error.AccessDenied`, including rename operations (such as the one used in
+/// this function).
 pub fn finish(self: *AtomicFile) FinishError!void {
     assert(self.file_exists);
     if (self.file_open) {

src/Builtin.zig+13-17

 @@ -280,24 +280,19 @@ pub fn populateFile(comp: *Compilation, mod: *Module, file: *File) !void {
 fn writeFile(file: *File, mod: *Module) !void {
     var buf: [std.fs.MAX_PATH_BYTES]u8 = undefined;
-    var af = mod.root.atomicFile(mod.root_src_path, .{ .make_path = true }, &buf) catch |err| {
+    var af = try mod.root.atomicFile(mod.root_src_path, .{ .make_path = true }, &buf);
-        std.log.warn("unable to create builtin atomic file '{}{s}'", .{
-            mod.root, mod.root_src_path,
-        });
-        return err;
-    };
     defer af.deinit();
-    af.file.writeAll(file.source) catch |err| {
+    try af.file.writeAll(file.source);
-        std.log.warn("unable to write builtin file data to '{}{s}'", .{
+    af.finish() catch |err| switch (err) {
-            mod.root, mod.root_src_path,
+        error.AccessDenied => switch (builtin.os.tag) {
-        });
+            .windows => {
-        return err;
+                // Very likely happened due to another process or thread
-    };
+                // simultaneously creating the same, correct builtin.zig file.
-    af.finish() catch |err| {
+                // This is not a problem; ignore it.
-        std.log.warn("unable to rename atomic builtin file into '{}{s}'", .{
+            },
-            mod.root, mod.root_src_path,
+            else => return err,
-        });
+        },
-        return err;
+        else => return err,
     };
     file.stat = .{
 @@ -307,6 +302,7 @@ fn writeFile(file: *File, mod: *Module) !void {
     };
 }
+const builtin = @import("builtin");
 const std = @import("std");
 const Allocator = std.mem.Allocator;
 const build_options = @import("build_options");