From 018548ddffeaa0bd878aabe2ebcc8d4946774aa9 Mon Sep 17 00:00:00 2001
From: Haohai Wen <haohai.wen@intel.com>
Date: Fri, 27 Jun 2025 07:39:04 +0800
Subject: [PATCH] [objcopy][coff] Place section name first in strtab (#145266)

The prioritized string table builder was introduced in 9cc9efc. This
patch sets highest priority for the section name to place it at the
start of string table to avoid the issue described in 4d2eda2.
---
 llvm/lib/ObjCopy/COFF/COFFWriter.cpp          |  7 ++--
 .../tools/llvm-objcopy/COFF/string-table.test | 34 +++++++++++++++++++
 2 files changed, 39 insertions(+), 2 deletions(-)
 create mode 100644 llvm/test/tools/llvm-objcopy/COFF/string-table.test

diff --git a/llvm/lib/ObjCopy/COFF/COFFWriter.cpp b/llvm/lib/ObjCopy/COFF/COFFWriter.cpp
index 734a1698d515..350c4aec572c 100644
--- a/llvm/lib/ObjCopy/COFF/COFFWriter.cpp
+++ b/llvm/lib/ObjCopy/COFF/COFFWriter.cpp
@@ -120,8 +120,11 @@ void COFFWriter::layoutSections() {
 
 Expected<size_t> COFFWriter::finalizeStringTable() {
   for (const auto &S : Obj.getSections())
-    if (S.Name.size() > COFF::NameSize)
-      StrTabBuilder.add(S.Name);
+    if (S.Name.size() > COFF::NameSize) {
+      // Put the section name at the start of strtab to ensure its offset is
+      // less than Max7DecimalOffset. Otherwise, lldb/gdb will not read it.
+      StrTabBuilder.add(S.Name, /*Priority=*/UINT8_MAX);
+    }
 
   for (const auto &S : Obj.getSymbols())
     if (S.Name.size() > COFF::NameSize)
diff --git a/llvm/test/tools/llvm-objcopy/COFF/string-table.test b/llvm/test/tools/llvm-objcopy/COFF/string-table.test
new file mode 100644
index 000000000000..aef710b69412
--- /dev/null
+++ b/llvm/test/tools/llvm-objcopy/COFF/string-table.test
@@ -0,0 +1,34 @@
+## Show that section names appear before symbol names in the COFF strtab.
+## These names are only added to the strtab if they exceed 8 characters.
+
+# RUN: yaml2obj %s -o %t
+# RUN: touch %t.sec
+# RUN: llvm-objcopy --add-section=.debug_str=%t.sec %t %t1
+# RUN: llvm-readobj --string-table %t1 | FileCheck %s
+
+# CHECK:      StringTable {
+# CHECK-NEXT:   Length: 37
+# CHECK-NEXT:   [     4] .debug_str
+# CHECK-NEXT:   [     f] symbol_zzz
+# CHECK-NEXT:   [    1a] symbol_aaa
+# CHECK-NEXT: }
+
+--- !COFF
+header:
+  Machine:         IMAGE_FILE_MACHINE_AMD64
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+symbols:
+  - Name:            symbol_aaa
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+  - Name:            symbol_zzz
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL