[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, 10 insertions, 3 deletions

diff --git a/llvm/include/llvm/Support/CommandLine.h b/llvm/include/llvm/Support/CommandLine.h
index cb85534ad8e..1fb95957244 100644
--- a/llvm/include/llvm/Support/CommandLine.h
+++ b/llvm/include/llvm/Support/CommandLine.h
@@ -175,7 +175,10 @@ enum MiscFlags {             // Miscellaneous flags to adjust argument
   // If this is enabled, multiple letter options are allowed to bunch together
   // with only a single hyphen for the whole group.  This allows emulation
   // of the behavior that ls uses for example: ls -la === ls -l -a
-  Grouping = 0x08
+  Grouping = 0x08,
+
+  // Default option
+  DefaultOption = 0x10
 };
 
 //===----------------------------------------------------------------------===//
@@ -270,7 +273,7 @@ class Option {
   unsigned Value : 2;
   unsigned HiddenFlag : 2; // enum OptionHidden
   unsigned Formatting : 2; // enum FormattingFlags
-  unsigned Misc : 4;
+  unsigned Misc : 5;
   unsigned Position = 0;       // Position of last occurrence of the option
   unsigned AdditionalVals = 0; // Greater than 0 for multi-valued option.
 
@@ -306,6 +309,7 @@ public:
   bool hasArgStr() const { return !ArgStr.empty(); }
   bool isPositional() const { return getFormattingFlag() == cl::Positional; }
   bool isSink() const { return getMiscFlags() & cl::Sink; }
+  bool isDefaultOption() const { return getMiscFlags() & cl::DefaultOption; }
 
   bool isConsumeAfter() const {
     return getNumOccurrencesFlag() == cl::ConsumeAfter;
@@ -382,7 +386,7 @@ public:
   }
 
   inline int getNumOccurrences() const { return NumOccurrences; }
-  inline void reset() { NumOccurrences = 0; }
+  void reset();
 };
 
 //===----------------------------------------------------------------------===//
@@ -1732,7 +1736,10 @@ class alias : public Option {
       error("cl::alias must have argument name specified!");
     if (!AliasFor)
       error("cl::alias must have an cl::aliasopt(option) specified!");
+    if (!Subs.empty())
+      error("cl::alias must not have cl::sub(), aliased option's cl::sub() will be used!");
     Subs = AliasFor->Subs;
+    Category = AliasFor->Category;
     addArgument();
   }