From 06879041acfe73e62f549a412d9f012a190113a3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Wed, 4 Feb 2026 00:00:06 +0100
Subject: [PATCH] link.Lld: disable parallel linking on NetBSD host

To work around NetBSD 10.1 malloc bugs.
---
 src/link/Lld.zig | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/link/Lld.zig b/src/link/Lld.zig
index fa94e534593a81c853c85911bf7054af03b65eab..5c7ba84623bde145063b4ff87b08434840ec43d9 100644
--- a/src/link/Lld.zig
+++ b/src/link/Lld.zig
@@ -356,6 +356,16 @@ fn linkAsArchive(lld: *Lld, arena: Allocator) !void {
     if (bad) return error.UnableToWriteArchive;
 }
 
+fn addCommonArgs(argv: *std.array_list.Managed([]const u8), coff: bool) !void {
+    if (builtin.os.tag == .netbsd) {
+        // NetBSD 10.1's `malloc` appears to have some nasty bugs that occur
+        // when doing parallel linking in LLD, manifesting as input and/or
+        // output section memory randomly being unmapped. So just don't do
+        // parallel linking for now.
+        try argv.append(if (coff) "-threads:1" else "--threads=1");
+    }
+}
+
 fn coffLink(lld: *Lld, arena: Allocator) !void {
     const comp = lld.base.comp;
     const gpa = comp.gpa;
@@ -418,6 +428,7 @@ fn coffLink(lld: *Lld, arena: Allocator) !void {
         // it calls exit() and does not reset all global data between invocations.
         const linker_command = "lld-link";
         try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
+        try addCommonArgs(&argv, true);
 
         if (target.isMinGW()) {
             try argv.append("-lldmingw");
@@ -836,6 +847,8 @@ fn elfLink(lld: *Lld, arena: Allocator) !void {
         // it calls exit() and does not reset all global data between invocations.
         const linker_command = "ld.lld";
         try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
+        try addCommonArgs(&argv, false);
+
         if (is_obj) {
             try argv.append("-r");
         }
@@ -1401,6 +1414,8 @@ fn wasmLink(lld: *Lld, arena: Allocator) !void {
         // it calls exit() and does not reset all global data between invocations.
         const linker_command = "wasm-ld";
         try argv.appendSlice(&[_][]const u8{ comp.self_exe_path.?, linker_command });
+        try addCommonArgs(&argv, false);
+
         try argv.append("--error-limit=0");
 
         if (comp.config.lto != .none) {
@@ -1724,6 +1739,7 @@ fn spawnLld(comp: *Compilation, arena: Allocator, argv: []const []const u8) !voi
     if (stderr.len > 0) log.warn("unexpected LLD stderr:\n{s}", .{stderr});
 }
 
+const builtin = @import("builtin");
 const std = @import("std");
 const Io = std.Io;
 const Allocator = std.mem.Allocator;
-- 
2.54.0