From 65492b3d5276d7a57f696fdc4da4d47f36909715 Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Tue, 16 Apr 2024 18:36:03 +0200
Subject: [PATCH] link/elf: skip empty merge sections when resolving

---
 src/link/Elf.zig             | 2 +-
 src/link/Elf/Object.zig      | 4 ++++
 src/link/Elf/relocatable.zig | 5 +++--
 3 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index c6d6d74436c93d820ecc77f676f6960d8a1dd30b..73082ab5f3eef2552e37aa06e9318c3f3a7dac36 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -3341,7 +3341,7 @@ pub fn addCommentString(self: *Elf) !void {
     res.sub.* = msub_index;
 }
 
-fn resolveMergeSections(self: *Elf) !void {
+pub fn resolveMergeSections(self: *Elf) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
diff --git a/src/link/Elf/Object.zig b/src/link/Elf/Object.zig
index 391ef9a55e179fe549725ef70990e69cf0296142..b652dc6790f11130614b793456c53c00ae39c115 100644
--- a/src/link/Elf/Object.zig
+++ b/src/link/Elf/Object.zig
@@ -283,6 +283,7 @@ fn initOutputSection(self: Object, elf_file: *Elf, shdr: elf.Elf64_Shdr) error{O
     const name = blk: {
         const name = self.getString(shdr.sh_name);
         if (elf_file.base.isRelocatable()) break :blk name;
+        if (shdr.sh_flags & elf.SHF_MERGE != 0) break :blk name;
         const sh_name_prefixes: []const [:0]const u8 = &.{
             ".text",       ".data.rel.ro", ".data", ".rodata", ".bss.rel.ro",       ".bss",
             ".init_array", ".fini_array",  ".tbss", ".tdata",  ".gcc_except_table", ".ctors",
@@ -740,6 +741,7 @@ pub fn resolveMergeSubsections(self: *Object, elf_file: *Elf) !void {
 
     for (self.merge_sections.items) |index| {
         const imsec = elf_file.inputMergeSection(index) orelse continue;
+        if (imsec.offsets.items.len == 0) continue;
         const msec = elf_file.mergeSection(imsec.merge_section_index);
         const atom_ptr = elf_file.atom(imsec.atom_index).?;
         const isec = atom_ptr.inputShdr(elf_file);
@@ -773,6 +775,7 @@ pub fn resolveMergeSubsections(self: *Object, elf_file: *Elf) !void {
 
         const imsec_index = self.merge_sections.items[esym.st_shndx];
         const imsec = elf_file.inputMergeSection(imsec_index) orelse continue;
+        if (imsec.offsets.items.len == 0) continue;
         const msub_index, const offset = imsec.findSubsection(@intCast(esym.st_value)) orelse {
             var err = try elf_file.addErrorWithNotes(2);
             try err.addMsg(elf_file, "invalid symbol value: {x}", .{esym.st_value});
@@ -797,6 +800,7 @@ pub fn resolveMergeSubsections(self: *Object, elf_file: *Elf) !void {
 
             const imsec_index = self.merge_sections.items[esym.st_shndx];
             const imsec = elf_file.inputMergeSection(imsec_index) orelse continue;
+            if (imsec.offsets.items.len == 0) continue;
             const msub_index, const offset = imsec.findSubsection(@intCast(@as(i64, @intCast(esym.st_value)) + rel.r_addend)) orelse {
                 var err = try elf_file.addErrorWithNotes(1);
                 try err.addMsg(elf_file, "invalid relocation at offset 0x{x}", .{rel.r_offset});
diff --git a/src/link/Elf/relocatable.zig b/src/link/Elf/relocatable.zig
index e7a984bc153749e8f7970aac001358b812dce82e..da15e4aa1499217c9d7b53db66b2e934570eda75 100644
--- a/src/link/Elf/relocatable.zig
+++ b/src/link/Elf/relocatable.zig
@@ -179,10 +179,11 @@ pub fn flushObject(elf_file: *Elf, comp: *Compilation, module_obj_path: ?[]const
     // input Object files.
     elf_file.resolveSymbols();
     elf_file.markEhFrameAtomsDead();
-    claimUnresolved(elf_file);
-
+    try elf_file.resolveMergeSections();
     try elf_file.addCommentString();
     try elf_file.sortMergeSections();
+    claimUnresolved(elf_file);
+
     try initSections(elf_file);
     try elf_file.sortShdrs();
     if (elf_file.zigObjectPtr()) |zig_object| {
-- 
2.54.0