[CommandLine] Don't allow unlimitted dashes for options. Part 1 or 5

[hintonda]

Summary

Prior to this patch, the CommandLine parser would strip an
unlimitted number of dashes from options. This patch limits it to
two.

This is the first of a set of patches that address how dashes are
handled by the CommandLine parser.

[rnk]

lgtm

Since we already have CommandLineTest.cpp, I think it would be reasonable to check that three dashes are rejected, but it's not necessary.

llvm/lib/Support/CommandLine.cpp

if (argv[i][0] != '-' || argv[i][1] == 0 || DashDashFound) {
       DashDashFound = true; // This is the mythical "--"?
       continue;             // Don't try to process it as an argument itself.
     } else if (ActivePositionalArg &&
                (ActivePositionalArg->getMiscFlags() & PositionalEatsArgs)) {
       // If there is a positional argument eating options, check to see if this
       // option is another positional argument.  If so, treat it as an argument,
       // otherwise feed it to the eating positional.
       ArgName = StringRef(argv[i] + 1);
-      // Eat leading dashes.
-      while (!ArgName.empty() && ArgName[0] == '-')
+      // Eat second dash.
+      if (!ArgName.empty() && ArgName[0] == '-')
         ArgName = ArgName.substr(1);
 
       Handler = LookupOption(*ChosenSubCommand, ArgName, Value);
       if (!Handler || Handler->getFormattingFlag() != cl::Positional) {
         ProvidePositionalOption(ActivePositionalArg, StringRef(argv[i]), i);
         continue; // We are done!
       }
 
     } else { // We start with a '-', must be an argument.
       ArgName = StringRef(argv[i] + 1);
-      // Eat leading dashes.
-      while (!ArgName.empty() && ArgName[0] == '-')
+      // Eat second dash.
+      if (!ArgName.empty() && ArgName[0] == '-')
         ArgName = ArgName.substr(1);
 
       Handler = LookupOption(*ChosenSubCommand, ArgName, Value);
 
       // Check to see if this "option" is really a prefixed or grouped argument.
       if (!Handler)
         Handler = HandlePrefixedOrGroupedOption(ArgName, Value, ErrorParsing,
                                                 OptionsMap);

llvm/test/DebugInfo/X86/array.ll

 ; ModuleID = 'array.c'
 ;
 ; From (clang -g -c -O1):
 ;
 ; void f(int* p) {
 ;   p[0] = 42;
 ; }
 ;
 ; int main(int argc, char** argv) {
 ;   int array[4] = { 0, 1, 2, 3 };
 ;   f(array);
 ;   return array[0];
 ; }
 ;
 ; RUN: llc -filetype=asm %s -o - | FileCheck %s
-; RUN: llc -filetype=obj %s -o - | llvm-dwarfdump -v - ---debug-info | FileCheck %s --check-prefix=DWARF
+; RUN: llc -filetype=obj %s -o - | llvm-dwarfdump -v - --debug-info | FileCheck %s --check-prefix=DWARF
 
 ; CHECK-LABEL: _main:
 ; CHECK: movaps {{.*}}, (%rsp)
 ; CHECK: movq    %rsp, %rdi
 ; CHECK: callq _f
 
 ; DWARF: DW_TAG_variable
 ; DWARF-NEXT:              DW_AT_location [DW_FORM_exprloc]      (DW_OP_fbreg +0)

llvm/test/DebugInfo/dwarfdump-64-bit-dwarf.test

 RUN: llvm-dwarfdump %p/Inputs/dwarfdump.elf-mips64-64-bit-dwarf \
-RUN:   ---debug-line | FileCheck %s
+RUN:   --debug-line | FileCheck %s
 
 # FIXME: llvm-dwarfdump's support for 64-bit dwarf is currently limited to
 # .debug_line.
 
 CHECK:   total_length: 0x00000212
 CHECK:        version: 2
 CHECK:prologue_length: 0x000001ab
 CHECK:min_inst_length: 1