[llvm-libtool-darwin] Add support for -V option

The -V option in cctools' libtool prints out the version number and
performs any specified operation. Add this option to LLVM's version.
cctools is more forgiving of invalid command lines when -V is specified,
but I think it's better to give errors instead of silently producing no
output.

Unfortunately, when -V is present, options that would otherwise be
required aren't anymore, so we need to perform some manual argument
validation.

Reviewed By: alexshap

Differential Revision: https://reviews.llvm.org/D86359

llvm/test/tools/llvm-libtool-darwin/invalid-input-output-args.test

@@ -10,7 +10,7 @@
 # RUN: not llvm-libtool-darwin -static %t.input 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=NO-OUTPUT
 
-# NO-OUTPUT: for the -o option: must be specified at least once!
+# NO-OUTPUT: for the -o option: must be specified
 
 ## Missing argument to -o:
 # RUN: not llvm-libtool-darwin -static %t.input -o 2>&1 | \
@@ -22,7 +22,7 @@
 # RUN: not llvm-libtool-darwin -static %t.input -o %t.lib1 -o %t.lib2 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=DOUBLE-OUTPUT
 
-# DOUBLE-OUTPUT: for the -o option: must occur exactly one time!
+# DOUBLE-OUTPUT: for the -o option: may only occur zero or one times!
 
 ## Input file not found:
 # RUN: not llvm-libtool-darwin -static -o %t.lib %t.missing 2>&1 | \

llvm/test/tools/llvm-libtool-darwin/missing-library-type.test

@@ -2,4 +2,4 @@
 # RUN: not llvm-libtool-darwin -o %t.lib %t.input 2>&1 | \
 # RUN:   FileCheck %s --check-prefix=MISSING-OPERATION
 
-# MISSING-OPERATION: Library Type: option: must be specified at least once!
+# MISSING-OPERATION: Library Type: option: must be specified

llvm/test/tools/llvm-libtool-darwin/version.test

@@ -0,0 +1,25 @@
+## Test the -V flag, which prints the version number to stdout. It also allows
+## for no operation to be specified, but if an operation is specified, it should
+## still occur and regular argument parsing errors should be surfaced (unlike
+## cctools libtool, which silences all argument parsing errors when -V is
+## specified).
+
+## Test -V by itself
+# RUN: llvm-libtool-darwin -V | FileCheck %s
+## The specific version number, vendor string, etc. will differ across
+## environments, so this is the most specific we can get.
+# CHECK: LLVM version
+
+## Parsing errors should not be surfaced when no operation is specified
+# RUN: llvm-libtool-darwin -V -D -U | FileCheck %s
+
+## Regular errors should occur when an operation is specified
+# RUN: not llvm-libtool-darwin -V -static 2>&1 | FileCheck --check-prefix=ERROR %s
+# ERROR: for the -o option: must be specified
+
+## A valid command line should print the version and perform the operation
+# RUN: yaml2obj %S/Inputs/input1.yaml -o %t-input1.o
+# RUN: yaml2obj %S/Inputs/input2.yaml -o %t-input2.o
+# RUN: llvm-libtool-darwin -static -o %t.lib %t-input1.o %t-input2.o -V | FileCheck %s
+# RUN: llvm-libtool-darwin -static -o %t2.lib %t-input1.o %t-input2.o
+# RUN: cmp %t.lib %t2.lib

llvm/tools/llvm-libtool-darwin/llvm-libtool-darwin.cpp

@@ -32,7 +32,7 @@ typedef std::map<uint64_t, std::vector<NewArchiveMember>>
 cl::OptionCategory LibtoolCategory("llvm-libtool-darwin Options");
 
 static cl::opt<std::string> OutputFile("o", cl::desc("Specify output filename"),
-                                       cl::value_desc("filename"), cl::Required,
+                                       cl::value_desc("filename"),
                                        cl::cat(LibtoolCategory));
 
 static cl::list<std::string> InputFiles(cl::Positional,
@@ -44,14 +44,14 @@ static cl::opt<std::string> ArchType(
     "arch_only", cl::desc("Specify architecture type for output library"),
     cl::value_desc("arch_type"), cl::ZeroOrMore, cl::cat(LibtoolCategory));
 
-enum class Operation { Static };
+enum class Operation { None, Static };
 
 static cl::opt<Operation> LibraryOperation(
     cl::desc("Library Type: "),
     cl::values(
         clEnumValN(Operation::Static, "static",
                    "Produce a statically linked library from the input files")),
-    cl::Required, cl::cat(LibtoolCategory));
+    cl::init(Operation::None), cl::cat(LibtoolCategory));
 
 static cl::opt<bool> DeterministicOption(
     "D", cl::desc("Use zero for timestamps and UIDs/GIDs (Default)"),
@@ -81,6 +81,10 @@ static cl::list<std::string> LibrarySearchDirs(
         " libraries"),
     cl::ZeroOrMore, cl::Prefix, cl::cat(LibtoolCategory));
 
+static cl::opt<bool>
+    VersionOption("V", cl::desc("Print the version number and exit"),
+                  cl::cat(LibtoolCategory));
+
 static const std::array<std::string, 3> StandardSearchDirs{
     "/lib",
     "/usr/lib",
@@ -444,6 +448,23 @@ static Expected<Config> parseCommandLine(int Argc, char **Argv) {
   Config C;
   cl::ParseCommandLineOptions(Argc, Argv, "llvm-libtool-darwin\n");
 
+  if (LibraryOperation == Operation::None) {
+    if (!VersionOption) {
+      std::string Error;
+      raw_string_ostream Stream(Error);
+      LibraryOperation.error("must be specified", "", Stream);
+      return createStringError(std::errc::invalid_argument, Error.c_str());
+    }
+    return C;
+  }
+
+  if (OutputFile.empty()) {
+    std::string Error;
+    raw_string_ostream Stream(Error);
+    OutputFile.error("must be specified", "o", Stream);
+    return createStringError(std::errc::invalid_argument, Error.c_str());
+  }
+
   if (DeterministicOption && NonDeterministicOption)
     return createStringError(std::errc::invalid_argument,
                              "cannot specify both -D and -U flags");
@@ -483,8 +504,13 @@ int main(int Argc, char **Argv) {
     return EXIT_FAILURE;
   }
 
+  if (VersionOption)
+    cl::PrintVersionMessage();
+
   Config C = *ConfigOrErr;
   switch (LibraryOperation) {
+  case Operation::None:
+    break;
   case Operation::Static:
     if (Error E = createStaticLibrary(C)) {
       WithColor::defaultErrorHandler(std::move(E));