[flang] Add runtime interface for COMMAND_ARGUMENT_COUNT

[klausler]

"environment.h" is not the right header for this.

The result type probably doesn't have to be an 64-bit integer.

[rovka]

Addressed review comments.

In the end I created a new file, command.h, because main.h is in the c-or-cpp style and I'm not sure it's a good idea to touch it. I don't mind hearing otherwise though :)

[rovka]

flang/runtime/command.h

10

That's weird, it's suggesting LLVM_FLANG_RUNTIME_COMMAND_H, but none of the other headers in the runtime have that kind of include guard (there are 3 FLANG_RUNTIME_*_H and plenty of FORTRAN_RUNTIME_*_H). The C++ style document isn't very specific on this either. What's the preference?

[klausler]

flang/runtime/command.h

10

That's weird, it's suggesting LLVM_FLANG_RUNTIME_COMMAND_H, but none of the other headers in the runtime have that kind of include guard (there are 3 FLANG_RUNTIME_*_H and plenty of FORTRAN_RUNTIME_*_H). The C++ style document isn't very specific on this either. What's the preference?

Our header guards correspond to namespaces, so FORTRAN_*_H.

[rovka]

flang/runtime/command.h

10

Ok, so the file should be fine then. I don't think we can tune the clang-tidy check for this, and we probably don't want to disable it altogether since then we'd miss out on real issues (i.e. missing header guards). Should I just commit as-is? Or does anyone have any other comments?

[jeanPerier]

Should I just commit as-is? Or does anyone have any other comments?

LGTM, you can go ahead.

flang/runtime/command.h

+//===-- runtime/command.h ---------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FORTRAN_RUNTIME_COMMAND_H_
+#define FORTRAN_RUNTIME_COMMAND_H_
+
+#include "cpp-type.h"
+#include "entry-names.h"
+
+namespace Fortran::runtime {
+extern "C" {
+// 16.9.51 COMMAND_ARGUMENT_COUNT
+//
+// Lowering may need to cast the result to match the precision of the default
+// integer kind.
+CppTypeFor<TypeCategory::Integer, 4> RTNAME(ArgumentCount)();
+}
+} // namespace Fortran::runtime
+
+#endif // FORTRAN_RUNTIME_COMMAND_H_