[CommandLineParser] Add DefaultOption flag

Summary: Add DefaultOption flag to CommandLineParser which provides a
default option or alias, but allows users to override it for some
other purpose as needed.

Also, add `-h` as a default alias to `-help`, which can be seamlessly
overridden by applications like llvm-objdump and llvm-readobj which
use `-h` as an alias for other options.

(relanding after revert, r358414)
Added DefaultOptions.clear() to reset().

Reviewers: alexfh, klimek

Reviewed By: klimek

Subscribers: kristina, MaskRay, mehdi_amini, inglorion, dexonsmith, hiraditya, llvm-commits, jhenderson, arphaman, cfe-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D59746

llvm-svn: 358428

1 files changed, 45 insertions, 5 deletions

diff --git a/llvm/lib/Support/CommandLine.cpp b/llvm/lib/Support/CommandLine.cpp
index 1858fe941ae..98d06f65c79 100644
--- a/llvm/lib/Support/CommandLine.cpp
+++ b/llvm/lib/Support/CommandLine.cpp
@@ -98,6 +98,11 @@ public:
   // This collects additional help to be printed.
   std::vector<StringRef> MoreHelp;
 
+  // This collects Options added with the cl::DefaultOption flag. Since they can
+  // be overridden, they are not added to the appropriate SubCommands until
+  // ParseCommandLineOptions actually runs.
+  SmallVector<Option*, 4> DefaultOptions;
+
   // This collects the different option categories that have been registered.
   SmallPtrSet<OptionCategory *, 16> RegisteredOptionCategories;
 
@@ -146,6 +151,11 @@ public:
   void addOption(Option *O, SubCommand *SC) {
     bool HadErrors = false;
     if (O->hasArgStr()) {
+      // If it's a DefaultOption, check to make sure it isn't already there.
+      if (O->isDefaultOption() &&
+          SC->OptionsMap.find(O->ArgStr) != SC->OptionsMap.end())
+        return;
+
       // Add argument to the argument map!
       if (!SC->OptionsMap.insert(std::make_pair(O->ArgStr, O)).second) {
         errs() << ProgramName << ": CommandLine Error: Option '" << O->ArgStr
@@ -185,7 +195,12 @@ public:
     }
   }
 
-  void addOption(Option *O) {
+  void addOption(Option *O, bool ProcessDefaultOption = false) {
+    if (!ProcessDefaultOption && O->isDefaultOption()) {
+      DefaultOptions.push_back(O);
+      return;
+    }
+
     if (O->Subs.empty()) {
       addOption(O, &*TopLevelSubCommand);
     } else {
@@ -201,8 +216,12 @@ public:
       OptionNames.push_back(O->ArgStr);
 
     SubCommand &Sub = *SC;
-    for (auto Name : OptionNames)
-      Sub.OptionsMap.erase(Name);
+    auto End = Sub.OptionsMap.end();
+    for (auto Name : OptionNames) {
+      auto I = Sub.OptionsMap.find(Name);
+      if (I != End && I->getValue() == O)
+        Sub.OptionsMap.erase(I);
+      }
 
     if (O->getFormattingFlag() == cl::Positional)
       for (auto Opt = Sub.PositionalOpts.begin();
@@ -266,8 +285,13 @@ public:
     if (O->Subs.empty())
       updateArgStr(O, NewName, &*TopLevelSubCommand);
     else {
-      for (auto SC : O->Subs)
-        updateArgStr(O, NewName, SC);
+      if (O->isInAllSubCommands()) {
+        for (auto SC : RegisteredSubCommands)
+          updateArgStr(O, NewName, SC);
+      } else {
+        for (auto SC : O->Subs)
+          updateArgStr(O, NewName, SC);
+      }
     }
   }
 
@@ -331,6 +355,8 @@ public:
     AllSubCommands->reset();
     registerSubCommand(&*TopLevelSubCommand);
     registerSubCommand(&*AllSubCommands);
+
+    DefaultOptions.clear();
   }
 
 private:
@@ -366,6 +392,13 @@ void Option::setArgStr(StringRef S) {
   ArgStr = S;
 }
 
+void Option::reset() {
+  NumOccurrences = 0;
+  setDefault();
+  if (isDefaultOption())
+    removeArgument();
+}
+
 // Initialise the general option category.
 OptionCategory llvm::cl::GeneralCategory("General options");
 
@@ -1167,6 +1200,10 @@ bool CommandLineParser::ParseCommandLineOptions(int argc,
   auto &SinkOpts = ChosenSubCommand->SinkOpts;
   auto &OptionsMap = ChosenSubCommand->OptionsMap;
 
+  for (auto O: DefaultOptions) {
+    addOption(O, true);
+  }
+
   if (ConsumeAfterOpt) {
     assert(PositionalOpts.size() > 0 &&
            "Cannot specify cl::ConsumeAfter without a positional argument!");
@@ -2146,6 +2183,9 @@ static cl::opt<HelpPrinterWrapper, true, parser<bool>>
         cl::location(WrappedNormalPrinter), cl::ValueDisallowed,
         cl::cat(GenericCategory), cl::sub(*AllSubCommands));
 
+static cl::alias HOpA("h", cl::desc("Alias for -help"), cl::aliasopt(HOp),
+                      cl::DefaultOption);
+
 static cl::opt<HelpPrinterWrapper, true, parser<bool>>
     HHOp("help-hidden", cl::desc("Display all available options"),
          cl::location(WrappedHiddenPrinter), cl::Hidden, cl::ValueDisallowed,