windows: ptrToInt and back the handle (*anyopaque)

Author: Jan Philipp Hafer

lib/std/child_process.zig

@@ -1633,13 +1633,22 @@ test "creating a child process with stdin and stdout behavior set to StdIo.Pipe"
 const child_str2 =
     \\ const std = @import("std");
     \\ const builtin = @import("builtin");
+    \\ const windowsPtrDigits = std.math.log10(std.math.maxInt(usize));
+    \\ const otherPtrDigits = std.math.log10(std.math.maxInt(u32)) + 1;
     \\ pub fn main() !void {
     \\     const alloc = std.testing.allocator;
     \\     const stdin = std.io.getStdIn();
     \\     const stdin_reader = stdin.reader();
     \\     const stdin_cont = try stdin_reader.readUntilDelimiterAlloc(alloc, '\n', 2_000);
     \\     defer alloc.free(stdin_cont);
-    \\     var file_handle = try std.fmt.parseInt(std.os.fd_t, stdin_cont, 11);
+    \\     var file_handle = file_handle: {
+    \\         if (builtin.target.os.tag == .windows) {
+    \\             var handle_int = try std.fmt.parseInt(usize, stdin_cont, windowsPtrDigits);
+    \\             break :file_handle @intToPtr(std.os.windows.HANDLE, handle_int);
+    \\         } else {
+    \\             break :file_handle try std.fmt.parseInt(std.os.fd_t, stdin_cont, otherPtrDigits);
+    \\         }
+    \\     };
     \\     var extra_stream_in = std.fs.File{ .handle = file_handle };
     \\     defer extra_stream_in.close();
     \\     const extra_str_in_rd = extra_stream_in.reader();
@@ -1650,15 +1659,32 @@ const child_str2 =
 ;
 
 fn testPipeInfo(self: *ChildProcess) ChildProcess.SpawnError!void {
+    const windowsPtrDigits: usize = std.math.log10(math.maxInt(usize));
+    const otherPtrDigits: usize = std.math.log10(math.maxInt(u32)) + 1; // +1 for sign
     if (self.extra_streams) |extra_streams| {
         for (extra_streams) |*extra| {
-            var buf: [11]u8 = [_]u8{0} ** 11; // -2**32 has 11 digits
+            const size = comptime size: {
+                if (builtin.target.os.tag == .windows) {
+                    break :size windowsPtrDigits;
+                } else {
+                    break :size otherPtrDigits;
+                }
+            };
+            var buf = comptime [_]u8{0} ** size;
             var s_chpipe_h: []u8 = undefined;
             std.debug.assert(extra.direction == .parent_to_child);
+            const handle = handle: {
+                if (builtin.target.os.tag == .windows) {
+                    // handle is *anyopaque and there is no other way to cast
+                    break :handle @ptrToInt(extra.*.input.?.handle);
+                } else {
+                    break :handle extra.*.input.?.handle;
+                }
+            };
             s_chpipe_h = std.fmt.bufPrint(
                 buf[0..],
                 "{d}",
-                .{extra.*.input.?.handle},
+                .{handle},
             ) catch unreachable;
             self.stdin.?.writer().writeAll(s_chpipe_h) catch unreachable;
             self.stdin.?.writer().writeAll("\n") catch unreachable;