From 29512f0edd9134ffe1f645ad69b5c4a3e1a7c7c3 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Wed, 3 Jul 2024 13:28:44 -0700
Subject: [PATCH] Compilation: don't give len=0 bufs to pwritev

The OS returns EFAULT for undefined pointers, even when len=0.
---
 src/Compilation.zig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Compilation.zig b/src/Compilation.zig
index 9d3a31e792..38651281b5 100644
--- a/src/Compilation.zig
+++ b/src/Compilation.zig
@@ -2827,6 +2827,9 @@ pub fn saveState(comp: *Compilation) !void {
 }
 
 fn addBuf(bufs_list: []std.posix.iovec_const, bufs_len: *usize, buf: []const u8) void {
+    // Even when len=0, the undefined pointer might cause EFAULT.
+    if (buf.len == 0) return;
+
     const i = bufs_len.*;
     bufs_len.* = i + 1;
     bufs_list[i] = .{