[llvm-objcopy] Add --strip-debug

[jakehehrlich]

Summary

Many projects use this option. There are two ways to use it. You can either a) Just use --strip-debug and keep the old file with debug content or b) you can use --strip-debug, --only-keep-debug, and --add-gnu-debuglink all in conjunction to create two separate files, the stripped file and the debug file. --only-keep-debug is more complicated than --strip-debug because it keeps the section headers without keeping section contents. That's not really supported by llvm-objcopy at the moment but I plan on adding it. So this change just supports a) and options to support b) will come soon.

[jhenderson]

LGTM, with one minor nit.

I noticed that we are being inconsistent with the capitalization of the help text for the different options. At some point, could you make a change to capitalize the first character of help text for options that aren't already in this state, to make it consistent with other LLVM tools, please.

tools/llvm-objcopy/llvm-objcopy.cpp

85 ↗

(On Diff #122506)

Removes -> Remove (for consistency with other options).

llvm/trunk/test/tools/llvm-objcopy/strip-debug.test

+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy -strip-debug %t %t2
+# RUN: llvm-readobj -file-headers -sections -symbols %t2 | FileCheck %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .debugfoo
+    Type:            SHT_PROGBITS
+    Content:         "00000000"
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:    0x0000000000000010
+    Content:         "00000000"
+Symbols:
+  Global:
+    - Name: foo
+      Section: .text
+    - Name: debugfoo
+      Section: .debugfoo
+
+# CHECK: SectionHeaderCount: 5
+
+# CHECK: Name: .text
+# CHECK: Name: .symtab
+# CHECK: Name: .strtab
+# CHECK: Name: .shstrtab
+
+# Check that *only* foo is copied and not debugfoo
+# CHECK:      Symbols [
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name:
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding:
+# CHECK-NEXT:     Type:
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: Undefined
+# CHECK-NEXT:   }
+# CHECK-NEXT:   Symbol {
+# CHECK-NEXT:     Name: foo
+# CHECK-NEXT:     Value:
+# CHECK-NEXT:     Size:
+# CHECK-NEXT:     Binding: Global
+# CHECK-NEXT:     Type:
+# CHECK-NEXT:     Other:
+# CHECK-NEXT:     Section: .text
+# CHECK-NEXT:   }
+# CHECK-NEXT: ]

llvm/trunk/tools/llvm-objcopy/llvm-objcopy.cpp

static cl::opt<std::string>
     OutputFormat("O", cl::desc("set output format to one of the following:"
                                "\n\tbinary"));
 static cl::list<std::string> ToRemove("remove-section",
                                       cl::desc("Remove a specific section"));
 static cl::alias ToRemoveA("R", cl::desc("Alias for remove-section"),
                            cl::aliasopt(ToRemove));
 static cl::opt<bool> StripAll("strip-all",
                               cl::desc("Removes symbol, relocation, and debug information"));
+static cl::opt<bool> StripDebug("strip-debug",
+                                cl::desc("Removes all debug information"));
 static cl::opt<bool> StripSections("strip-sections",
                                    cl::desc("Remove all section headers"));
 static cl::opt<bool>
     StripDWO("strip-dwo", cl::desc("remove all DWARF .dwo sections from file"));
 static cl::opt<bool> ExtractDWO(
     "extract-dwo",
     cl::desc("remove all sections that are not DWARF .dwo sections from file"));
 static cl::opt<std::string>
void CopyBinary(const ELFObjectFile<ELF64LE> &ObjFile) {
 
   if (StripSections) {
     RemovePred = [RemovePred](const SectionBase &Sec) {
       return RemovePred(Sec) || (Sec.Flags & SHF_ALLOC) == 0;
     };
     Obj->WriteSectionHeaders = false;
   }
 
+  if (StripDebug) {
+    RemovePred = [RemovePred](const SectionBase &Sec) {
+      return RemovePred(Sec) || Sec.Name.startswith(".debug");
+    };
+  }
+
   Obj->removeSections(RemovePred);
   Obj->finalize();
   WriteObjectFile(*Obj, OutputFilename.getValue());
 }
 
 int main(int argc, char **argv) {
   // Print a stack trace if we signal out.
   sys::PrintStackTraceOnErrorSignal(argv[0]);