[CommandLine] Error message for incorrect PositionalEatArgs usage

Summary:
bugpoint has several options specified as `PositionalEatArgs` to pass
options through to the underlying tool, e.g. `-tool-args`. The `-help`
message suggests the usage is: `-tool-args=<string>`. However, this is
misleading, because that's not how these arguments work. Rather than taking
a value, the option consumes all positional arguments until the next
recognized option (or all arguments if `--` is specified at some point).
To make this slightly clearer, instead print the help as:
```
  -tool-args <string>...                            - <tool arguments>...
```
Additionally, add an error if the user attempts to use a `PositionalEatArgs`
argument with a value, instead of silently ignoring it. Example:
```
./bin/bugpoint -tool-args=-mpcu=skylake-avx512
bugpoint: for the -tool-args option: This argument does not take a value.
    Instead, it consumes any positional arguments until the next recognized option.
```

Reviewed By: aprantl
Differential Revision: https://reviews.llvm.org/D46787

llvm-svn: 332311

1 files changed, 19 insertions, 0 deletions

diff --git a/llvm/unittests/Support/CommandLineTest.cpp b/llvm/unittests/Support/CommandLineTest.cpp
index 8657504..a52420f 100644
--- a/llvm/unittests/Support/CommandLineTest.cpp
+++ b/llvm/unittests/Support/CommandLineTest.cpp
@@ -816,4 +816,23 @@ TEST(CommandLineTest, ReadConfigFile) {
   llvm::sys::fs::remove(TestDir);
 }
 
+TEST(CommandLineTest, PositionalEatArgsError) {
+  static cl::list<std::string> PosEatArgs("positional-eat-args", cl::Positional,
+    cl::desc("<arguments>..."), cl::ZeroOrMore,
+    cl::PositionalEatsArgs);
+
+  const char *args[] = {"prog", "-positional-eat-args=XXXX"};
+  const char *args2[] = {"prog", "-positional-eat-args=XXXX", "-foo"};
+  const char *args3[] = {"prog", "-positional-eat-args", "-foo"};
+
+  std::string Errs;
+  raw_string_ostream OS(Errs);
+  EXPECT_FALSE(cl::ParseCommandLineOptions(2, args, StringRef(), &OS)); OS.flush();
+  EXPECT_FALSE(Errs.empty()); Errs.clear();
+  EXPECT_FALSE(cl::ParseCommandLineOptions(3, args2, StringRef(), &OS)); OS.flush();
+  EXPECT_FALSE(Errs.empty()); Errs.clear();
+  EXPECT_TRUE(cl::ParseCommandLineOptions(3, args3, StringRef(), &OS)); OS.flush();
+  EXPECT_TRUE(Errs.empty());
+}
+
 }  // anonymous namespace