From 97ee88cbf3afc6483b8c22e5e6e9471a34d01020 Mon Sep 17 00:00:00 2001
From: Matthew Lugg <mlugg@mlugg.co.uk>
Date: Thu, 24 Sep 2026 17:06:42 +0200
Subject: [PATCH] Elf2: correctly pad debug sections even when there is no ZCU

---
 src/link/Elf2.zig | 92 ++++++++++++++++++++++++-----------------------
 1 file changed, 47 insertions(+), 45 deletions(-)

diff --git a/src/link/Elf2.zig b/src/link/Elf2.zig
index df3287170fc6b2247f8ac98ff4d9b6cde9954ff2..fdb5b0704402317e54207b754629ba8d408d7708 100644
--- a/src/link/Elf2.zig
+++ b/src/link/Elf2.zig
@@ -8301,6 +8301,53 @@ pub fn prelink(elf: *Elf, prog_node: std.Progress.Node) link.Error!void {
 fn prelinkInner(elf: *Elf) Error!void {
     const comp = elf.base.comp;
     const gpa = comp.gpa;
+
+    const addr_align: Alignment = switch (elf.identClass()) {
+        .NONE, _ => unreachable,
+        .@"32" => .@"4",
+        .@"64" => .@"8",
+    };
+    try elf.nodes.ensureUnusedCapacity(gpa, 7 + 5);
+    for ([7]Section.Index{
+        elf.shndx.debug_addr,
+        elf.shndx.eh_frame,
+        elf.shndx.debug_frame,
+        elf.shndx.debug_info,
+        elf.shndx.debug_line,
+        elf.shndx.debug_rnglists,
+        elf.shndx.debug_str_offsets,
+    }) |debug_shndx| {
+        if (debug_shndx == .UNDEF) continue;
+        const debug_ni = debug_shndx.get(elf).ni;
+        const frame_format = debug_shndx.debugFrameFormat(elf);
+        const unit_padding_ni = elf.addNodeAssumeCapacity(
+            try debug_ni.addHeaderChildAfter(gpa, &elf.mf, last_header_oni: {
+                var last_header_oni = debug_ni.last(&elf.mf);
+                while (last_header_oni.unwrap()) |last_header_ni|
+                    switch (last_header_ni.position(&elf.mf)) {
+                        .header => break,
+                        .footer => last_header_oni = last_header_ni.prev(&elf.mf),
+                        .floating => unreachable,
+                    };
+                break :last_header_oni last_header_oni;
+            }, .{
+                .alignment = if (frame_format) |_| addr_align else .@"1",
+                .next_moved = true,
+                .enable_next_moved = true,
+            }),
+            .unit_padding,
+        );
+        var debug_nw: MappedFile.Node.Writer = undefined;
+        unit_padding_ni.writer(gpa, &elf.mf, &debug_nw);
+        defer debug_nw.deinit();
+        (if (frame_format) |format|
+            elf.dwarf.genDebugFrameCie(&debug_nw.interface, null, format)
+        else
+            elf.dwarf.genUnitPadding(&debug_nw.interface)) catch |err| switch (err) {
+            error.WriteFailed => return debug_nw.err.?,
+        };
+    }
+
     if (comp.zcu) |_| self_hosted_codegen: {
         if (comp.config.use_llvm) break :self_hosted_codegen;
 
@@ -8323,51 +8370,6 @@ fn prelinkInner(elf: *Elf) Error!void {
         };
         elf.input_pending_index += 1;
 
-        const addr_align: Alignment = switch (elf.identClass()) {
-            .NONE, _ => unreachable,
-            .@"32" => .@"4",
-            .@"64" => .@"8",
-        };
-        try elf.nodes.ensureUnusedCapacity(gpa, 7 + 5);
-        for ([7]Section.Index{
-            elf.shndx.debug_addr,
-            elf.shndx.eh_frame,
-            elf.shndx.debug_frame,
-            elf.shndx.debug_info,
-            elf.shndx.debug_line,
-            elf.shndx.debug_rnglists,
-            elf.shndx.debug_str_offsets,
-        }) |debug_shndx| {
-            if (debug_shndx == .UNDEF) continue;
-            const debug_ni = debug_shndx.get(elf).ni;
-            const frame_format = debug_shndx.debugFrameFormat(elf);
-            const unit_padding_ni = elf.addNodeAssumeCapacity(
-                try debug_ni.addHeaderChildAfter(gpa, &elf.mf, last_header_oni: {
-                    var last_header_oni = debug_ni.last(&elf.mf);
-                    while (last_header_oni.unwrap()) |last_header_ni|
-                        switch (last_header_ni.position(&elf.mf)) {
-                            .header => break,
-                            .footer => last_header_oni = last_header_ni.prev(&elf.mf),
-                            .floating => unreachable,
-                        };
-                    break :last_header_oni last_header_oni;
-                }, .{
-                    .alignment = if (frame_format) |_| addr_align else .@"1",
-                    .next_moved = true,
-                    .enable_next_moved = true,
-                }),
-                .unit_padding,
-            );
-            var debug_nw: MappedFile.Node.Writer = undefined;
-            unit_padding_ni.writer(gpa, &elf.mf, &debug_nw);
-            defer debug_nw.deinit();
-            (if (frame_format) |format|
-                elf.dwarf.genDebugFrameCie(&debug_nw.interface, null, format)
-            else
-                elf.dwarf.genUnitPadding(&debug_nw.interface)) catch |err| switch (err) {
-                error.WriteFailed => return debug_nw.err.?,
-            };
-        }
         switch (elf.shndx.debug_addr) {
             .UNDEF => {},
             else => |debug_addr_shndx| {
-- 
2.54.0