r199247 - Clarify driver/frontend -fms-compatibility help text

[Alp Toker]

On 15/01/2014 05:59, Nico Weber wrote:
> On Tue, Jan 14, 2014 at 11:13 AM, Alp Toker <alp at nuanti.com 
> <mailto:alp at nuanti.com>> wrote:
>
>     Author: alp
>     Date: Tue Jan 14 13:13:00 2014
>     New Revision: 199247
>
>     URL: http://llvm.org/viewvc/llvm-project?rev=199247&view=rev
>     Log:
>     Clarify driver/frontend -fms-compatibility help text
>
>     Better describe the flag that enables drop-in MSVC compatibility,
>     including
>     ability to parse MS standard headers. This is intended to
>     distinguish it from
>     -fms-extensions, the more established and 'gentler' flag also
>     supported by GCC.
>
>     The new wording matches up with the internal description
>     introduced in r198936.
>     Still room for improvement (e.g. C++ is part of the product name,
>     yet the flag
>     also applies to C) but it's a step forward from "Microsoft mode".
>
>     Modified:
>         cfe/trunk/include/clang/Driver/Options.td
>
>     Modified: cfe/trunk/include/clang/Driver/Options.td
>     URL:
>     http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Driver/Options.td?rev=199247&r1=199246&r2=199247&view=diff
>     ==============================================================================
>     --- cfe/trunk/include/clang/Driver/Options.td (original)
>     +++ cfe/trunk/include/clang/Driver/Options.td Tue Jan 14 13:13:00 2014
>     @@ -575,9 +575,9 @@ def fmessage_length_EQ : Joined<["-"], "
>      def fms_extensions : Flag<["-"], "fms-extensions">,
>     Group<f_Group>, Flags<[CC1Option]>,
>        HelpText<"Accept some non-standard constructs supported by the
>     Microsoft compiler">;
>      def fms_compatibility : Flag<["-"], "fms-compatibility">,
>     Group<f_Group>, Flags<[CC1Option]>,
>     -  HelpText<"Enable Microsoft compatibility mode">;
>     +  HelpText<"Enable full Microsoft Visual C++ compatibility">;
>
>
> Isn't "full" too strong? I thought this was more "enough to parse ms 
> sdk headers and link to mscrt", not "full" compatibility.

It isn't perfect, but we ran through a lot of options and this is the 
only one that standard.

In so far as it enables the "full" set of compatibility features this 
one works well.


Other options evaluated:

  * "drop-in": Sounds like a knock off or clone, and could be taken
    literally (I deleted cl.exe and dropped it in!)
  * "seamless": Implies subtlety and non-breaking of existing code,
    which isn't always the case.
  * No word: Same problem as 'seamless'. "Compatible with existing code,
    or compatible with MSVC?"
  * "mode": There are other modes which only make minor changes to the
    parser -- this didn't work out in past
  * "Microsoft system headers": none -fms-compatibility is currently
    restricted to system headers -- it fully changes the behaviour of
    the compiler in various ways.


Also, facepalm link:

   "Clang does't compile gcc compatible c++ code? -fms-compatibility is 
your friend"
http://codingdave.blogspot.co.uk/2012/08/clang-doest-compile-gcc-compatible-c.html

/"Although this parameter was introduced to make clang compile visual 
c++ headers, it also fixes problems like the one above."/

That's why we'd do well to move away from the "ms sdk header" wording 
(even if it's the current goal).

I think it's about right now, but suggestions on the back of a postcard 
welcome.

Alp.


>      def fmsc_version : Joined<["-"], "fmsc-version=">,
>     Group<f_Group>, Flags<[CC1Option, CoreOption]>,
>     -  HelpText<"Version of the Microsoft C/C++ compiler to report in
>     _MSC_VER (0 = don't define it (default))">;
>     +  HelpText<"Microsoft compiler version number to report in
>     _MSC_VER (0 = don't define it (default))">;
>      def fdelayed_template_parsing : Flag<["-"],
>     "fdelayed-template-parsing">, Group<f_Group>,
>        HelpText<"Parse templated function definitions at the end of the "
>                 "translation unit">,  Flags<[CC1Option]>;
>
>
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