[llvm-objcopy] Add -S option to llvm-objcopy and llvm-strip

[jakehehrlich]

Summary

-S means something different in GNU strip and GNU objcopy. We'd like to have the respective llvm versions maintain command line compatibility. In strip it means --strip-debug and in objcopy it means --strip-all. This change adds support for -S to both.

[jhenderson]

Why is -S a hidden option?

tools/llvm-objcopy/llvm-objcopy.cpp

354

This line hasn't been clang-formatted.

[jakehehrlich]

In D41141#953572, @jhenderson wrote:

Why is -S a hidden option?

It can't be given a consistent description across llvm-objcopy and llvm-strip (it's also the only option that has that property). It's also consistent with aliases for the long name options being hidden. In my mind it's really there for command line compatibility and nothing else.

[jhenderson]

Okay, LGTM, with the clang-formatting comment addressed.

test/tools/llvm-objcopy/big-S.test

+UN: yaml2obj %s > %t
+# RUN: llvm-strip -S %t -o %t2
+# RUN: llvm-readobj -file-headers -sections -symbols %t2 | FileCheck --check-prefix=STRIP %s
+# RUN: llvm-objcopy -S %t %t2
+# RUN: llvm-readobj -file-headers -sections -symbols %t2 | FileCheck --check-prefix=OBJCOPY %s
+
+!ELF
+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+Sections:
+  - Name:            .bss
+    Type:            SHT_NOBITS
+    Flags:           [ SHF_ALLOC ]
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Content:         "c3c3c3c3"
+  - Name:            .blarg
+    Type:            SHT_PROGBITS
+    Flags:           [ ]
+    Content:         "00000000"
+  - Name:            .debugfoo
+    Type:            SHT_PROGBITS
+    Content:         "00000000"
+  - Name:            .gnu.warning.foo
+    Type:            SHT_PROGBITS
+
+# STRIP: SectionHeaderCount: 8
+
+# STRIP: Name: .bss
+# STRIP: Name: .text
+# STRIP: Name: .blarg
+# STRIP: Name: .gnu.warning.foo
+# STRIP: Name: .symtab
+# STRIP: Name: .strtab
+# STRIP: Name: .shstrtab
+
+# OBJCOPY: SectionHeaderCount: 5
+
+# OBJCOPY: Name: .bss
+# OBJCOPY: Name: .text
+# OBJCOPY: Name: .gnu.warning.foo
+# OBJCOPY: Name: .shstrtab

tools/llvm-objcopy/llvm-objcopy.cpp

static cl::list<std::string> ToRemove("remove-section",
                                       cl::desc("Remove <section>"),
                                       cl::value_desc("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 non-allocated sections other than .gnu.warning* sections"));
+static cl::opt<bool> BigS("S", cl::Hidden);
 static cl::opt<bool>
     StripAllGNU("strip-all-gnu",
                 cl::desc("Removes symbol, relocation, and debug information"));
 static cl::list<std::string> Keep("keep", cl::desc("Keep <section>"),
                                   cl::value_desc("section"));
 static cl::list<std::string> OnlyKeep("only-keep",
                                       cl::desc("Remove all but <section>"),
                                       cl::value_desc("section"));
void CommonConfig(CopyConfig<ELFT>& Config) {
   Config.StripDebug = StripDebug;
   Config.StripNonAlloc = StripNonAlloc;
 }
 
 template <class ELFT>
 void Strip(const ELFObjectFile<ELFT>& ObjFile) {
   CopyConfig<ELFT> Config(ObjFile);
   CommonConfig(Config);
+  Config.StripDebug = Config.StripDebug || BigS;
   Config.StripAll = StripAll ||
-                    !(StripAllGNU || StripDebug || StripDWO || StripNonAlloc ||
+                    !(StripAllGNU || Config.StripDebug || StripDWO || StripNonAlloc ||
                       StripSections);
   Config.copyBinary();
 }
 
 template <class ELFT>
 void Objcopy(const ELFObjectFile<ELFT>& ObjFile) {
   CopyConfig<ELFT> Config(ObjFile);
   CommonConfig(Config);
-  Config.StripAll = StripAll;
+  Config.StripAll = StripAll || BigS;
   Config.copyBinary();
 }
 
 }
 
 template <class ELFT>
 void InvokeMain(const ELFObjectFile<ELFT>& ObjFile) {
   StringRef Stem = sys::path::stem(ToolName);