[llvm-readobj] Support --string-table for COFF (#141552)

Author: HaohaiWen

llvm/include/llvm/Object/COFF.h

@@ -939,6 +939,10 @@ class COFFObjectFile : public ObjectFile {
     return uintptr_t(0);
   }
 
+  StringRef getStringTable() const {
+    return StringRef(StringTable, StringTableSize);
+  }
+
   uint16_t getMachine() const {
     if (COFFHeader) {
       if (CHPEMetadata) {

llvm/test/tools/llvm-readobj/COFF/string-table.test

@@ -0,0 +1,37 @@
+# RUN: yaml2obj %s -o %t.obj
+# RUN: llvm-readobj --string-table %t.obj \
+# RUN:   %p/Inputs/coff-load-config-x64.dll \
+# RUN:   %p/Inputs/zero-string-table.obj.coff-i386 | FileCheck %s
+
+# CHECK-LABEL: File: {{.*}}string-table.test.tmp.obj
+# CHECK:       StringTable {
+# CHECK-NEXT:    Length: 31
+# CHECK-NEXT:    [     4] .debug_str
+# CHECK-NEXT:    [     f] _main_test_test
+# CHECK-NEXT:  }
+
+# CHECK-LABEL: File: {{.*}}coff-load-config-x64.dll
+# CHECK:       StringTable {
+# CHECK-NEXT:    Length: 0
+# CHECK-NEXT:  }
+
+# CHECK-LABEL: File: {{.*}}zero-string-table.obj.coff-i386
+# CHECK:       StringTable {
+# CHECK-NEXT:    Length: 4
+# 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 ]
+  - Name:            .debug_str
+    Characteristics: [ IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_DISCARDABLE, IMAGE_SCN_MEM_READ ]
+symbols:
+  - Name:            _main_test_test
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL

llvm/tools/llvm-readobj/COFFDumper.cpp

@@ -108,6 +108,7 @@ class COFFDumper : public ObjDumper {
   void printStackMap() const override;
   void printAddrsig() override;
   void printCGProfile() override;
+  void printStringTable() override;
 
 private:
   StringRef getSymbolName(uint32_t Index);
@@ -2219,6 +2220,17 @@ void COFFDumper::printCGProfile() {
   }
 }
 
+void COFFDumper::printStringTable() {
+  DictScope DS(W, "StringTable");
+  StringRef StrTable = Obj->getStringTable();
+  uint32_t StrTabSize = StrTable.size();
+  W.printNumber("Length", StrTabSize);
+  // Print strings from the fifth byte, since the first four bytes contain the
+  // length (in bytes) of the string table (including the length field).
+  if (StrTabSize > 4)
+    printAsStringList(StrTable, 4);
+}
+
 StringRef COFFDumper::getSymbolName(uint32_t Index) {
   Expected<COFFSymbolRef> Sym = Obj->getSymbol(Index);
   if (!Sym)

llvm/tools/llvm-readobj/ObjDumper.h

@@ -157,8 +157,10 @@ class ObjDumper {
                      llvm::codeview::GlobalTypeTableBuilder &GlobalCVTypes,
                      bool GHash) {}
 
-  // Only implemented for XCOFF.
+  // Only implemented for XCOFF/COFF.
   virtual void printStringTable() {}
+
+  // Only implemented for XCOFF.
   virtual void printAuxiliaryHeader() {}
   virtual void printExceptionSection() {}
   virtual void printLoaderSection(bool PrintHeader, bool PrintSymbols,

llvm/tools/llvm-readobj/Opts.td

@@ -44,7 +44,7 @@ defm sort_symbols : Eq<"sort-symbols", "Specify the keys to sort the symbols bef
 def stack_sizes : FF<"stack-sizes", "Display contents of all stack sizes sections. This option has no effect for GNU style output">;
 def stackmap : FF<"stackmap", "Display contents of stackmap section">;
 defm string_dump : Eq<"string-dump", "Display the specified section(s) as a list of strings">, MetaVarName<"<name or index>">;
-def string_table : FF<"string-table", "Display the string table (only for XCOFF now)">;
+def string_table : FF<"string-table", "Display the string table (only for XCOFF/COFF now)">;
 def symbols : FF<"symbols", "Display the symbol table. Also display the dynamic symbol table when using GNU output style for ELF">;
 def unwind : FF<"unwind", "Display unwind information">;