potentially incorrect Emacs marker in headers

[firewave]

According to https://llvm.org/docs/CodingStandards.html#file-headers the way to tell Emacs that a file is C++ is -*- C++ -*-.

But while implementing and testing support for this I ran into a few files which appears to have mistakes in that. Those markers are looking like this:

-*- C++ --*-
-*- C++ ---*-
-*- C++ ------*-
-*- C++ -------*-
-*- C++ --------*-
-*- C++ ---------*-
-*- C++ ----------*-
-*- C++/-*-

Since it is really hard to find a proper specification for this I cannot tell if these would actually be valid. But since no other files in the /usr/include of my distro have such markers I assume they are wrong.

Here is the list of affected files.

/usr/include/clang/Analysis/Analyses/LiveVariables.h
/usr/include/clang/Analysis/Analyses/ReachableCode.h
/usr/include/clang/Analysis/Analyses/ThreadSafetyLogical.h
/usr/include/clang/Tooling/AllTUsExecution.h
/usr/include/clang/Tooling/Execution.h
/usr/include/clang/Tooling/StandaloneExecution.h
/usr/include/clang/Tooling/Syntax/Mutations.h
/usr/include/llvm/Analysis/InlineAdvisor.h
/usr/include/llvm/Analysis/InlineOrder.h
/usr/include/llvm/Analysis/ReplayInlineAdvisor.h
/usr/include/llvm/BinaryFormat/DXContainer.h
/usr/include/llvm/BinaryFormat/XCOFF.h
/usr/include/llvm/MC/MCDXContainerWriter.h
/usr/include/llvm/Remarks/RemarkFormat.h
/usr/include/llvm/Remarks/Remark.h
/usr/include/llvm/Remarks/RemarkLinker.h
/usr/include/llvm/Remarks/RemarkParser.h
/usr/include/llvm/Remarks/RemarkStringTable.h
/usr/include/llvm/Transforms/Utils/MemoryOpRemark.h

While at it, it might also make sense to check if there are files which are completely lacking the marker.

[firewave]

It is also not clear if the marker is supported in /* */ comments. I see this in some files

/*===- TableGen'erated file -------------------------------------*- C++ -*-===*\

Even if that marker is correct the different comment style seems to stray from the coding standard.

I also checked part of the headers for the marker and there are several which are missing it. The command is find /usr/include/clang -type f | xargs -n 1 head -n 1 | grep -v "\-\*\-".

[firewave]

Using /* */ is obviously valid because the marker is language-agnostic and // comments are C++-specific.

There appears to be more variations on faulty markers:
//===- RecordName.h ------------------------------------------- *- C++ --*-===//

[firewave]

Preliminary command to detect the most basic incorrect markers:
find -type f -name '*.h' | xargs -n 1 head -n1 | grep '\/\/===' | grep 'C++' | grep -v '\-\*- C++ -\*-'

There are also several comments without any marker at all.

This obviously needs some tooling which checks/injects these. Is there tooling for generating these comments or do they have just been copy and pasted since they were introduced?

[firewave]

Closing as Emacs markers are no longer required by the style guide: #118553.