Re: [commit: ghc] master: Adds -ghc-version flag to ghc. (12a7444)

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Re: [commit: ghc] master: Adds -ghc-version flag to ghc. (12a7444)

Gabor Greif-2
Hmm, when seeing "-ghc-version" I first thought

  why a new flag for querying the version of GHC?

But the flag has a different purpose!

I'd suggest to rename it to "-ghcversion-file" or similar.

Just my two cents...

Cheers,

    Gabor

On 11/18/17, [hidden email] <[hidden email]> wrote:

> Repository : ssh://[hidden email]/ghc
>
> On branch  : master
> Link       :
> http://ghc.haskell.org/trac/ghc/changeset/12a7444463184e9eddbe7b7251a0ee1e976f4d75/ghc
>
>>---------------------------------------------------------------
>
> commit 12a7444463184e9eddbe7b7251a0ee1e976f4d75
> Author: Moritz Angermann <[hidden email]>
> Date:   Fri Nov 17 19:29:25 2017 +0800
>
>     Adds -ghc-version flag to ghc.
>
>     Summary:
>     When building the rts with ghc (e.g. using ghc as a c compiler), ghc's
>     "Value Add"[1] is, it includes adding `-include /path/to/ghcversion.h`.
> For
>     this it looksup the rts package in the package database, which--if
>     empty--fails.  Thus to allow compiling C files with GHC, we add the
>     `-ghc-version` flag, which takes the path to the `ghcversion.h` file.
>
>     A `-no-ghc-version` flag was omitted, as at that point it becomes
>     questionable why one would use ghc to compile c if one doesn't
>     any of the added value.
>
>     --
>
>     [1] from `compiler/main/DriverPipeline.hs`
>     >        -- add package include paths even if we're just compiling .c
>     >        -- files; this is the Value Add(TM) that using ghc instead of
>     >        -- gcc gives you :)
>
>     Reviewers: bgamari, geekosaur, austin
>
>     Reviewed By: bgamari
>
>     Subscribers: rwbarton, thomie
>
>     Differential Revision: https://phabricator.haskell.org/D4135
>
>
>>---------------------------------------------------------------
>
> 12a7444463184e9eddbe7b7251a0ee1e976f4d75
>  compiler/main/DriverPipeline.hs | 11 ++++++++---
>  compiler/main/DynFlags.hs       |  7 +++++++
>  docs/users_guide/using.rst      | 23 +++++++++++++++++++++++
>  3 files changed, 38 insertions(+), 3 deletions(-)
>
> diff --git a/compiler/main/DriverPipeline.hs
> b/compiler/main/DriverPipeline.hs
> index fab7fad..4f7bfbd 100644
> --- a/compiler/main/DriverPipeline.hs
> +++ b/compiler/main/DriverPipeline.hs
> @@ -2204,11 +2204,16 @@ touchObjectFile dflags path = do
>  -- | Find out path to @ghcversion.h@ file
>  getGhcVersionPathName :: DynFlags -> IO FilePath
>  getGhcVersionPathName dflags = do
> -  dirs <- getPackageIncludePath dflags [toInstalledUnitId rtsUnitId]
> +  candidates <- case ghcVersion dflags of
> +    Just path -> return [path]
> +    Nothing -> (map (</> "ghcversion.h")) <$>
> +               (getPackageIncludePath dflags [toInstalledUnitId rtsUnitId])
>
> -  found <- filterM doesFileExist (map (</> "ghcversion.h") dirs)
> +  found <- filterM doesFileExist candidates
>    case found of
> -      []    -> throwGhcExceptionIO (InstallationError ("ghcversion.h
> missing"))
> +      []    -> throwGhcExceptionIO (InstallationError
> +                                    ("ghcversion.h missing; tried: "
> +                                      ++ intercalate ", " candidates))
>        (x:_) -> return x
>
>  -- Note [-fPIC for assembler]
> diff --git a/compiler/main/DynFlags.hs b/compiler/main/DynFlags.hs
> index 5888acc..04ac635 100644
> --- a/compiler/main/DynFlags.hs
> +++ b/compiler/main/DynFlags.hs
> @@ -534,6 +534,7 @@ data GeneralFlag
>     | Opt_ExternalInterpreter
>     | Opt_OptimalApplicativeDo
>     | Opt_VersionMacros
> +   | Opt_GhcVersion
>     | Opt_WholeArchiveHsLibs
>
>     -- PreInlining is on by default. The option is there just to see how
> @@ -917,6 +918,7 @@ data DynFlags = DynFlags {
>    flushOut              :: FlushOut,
>    flushErr              :: FlushErr,
>
> +  ghcVersion            :: Maybe FilePath,
>    haddockOptions        :: Maybe String,
>
>    -- | GHCi scripts specified by -ghci-script, in reverse order
> @@ -1682,6 +1684,7 @@ defaultDynFlags mySettings myLlvmTargets =
>          filesToClean   = panic "defaultDynFlags: No filesToClean",
>          dirsToClean    = panic "defaultDynFlags: No dirsToClean",
>          generatedDumps = panic "defaultDynFlags: No generatedDumps",
> +        ghcVersion     = Nothing,
>          haddockOptions = Nothing,
>          dumpFlags = EnumSet.empty,
>          generalFlags = EnumSet.fromList (defaultFlags mySettings),
> @@ -2339,6 +2342,9 @@ addDepSuffix s d = d { depSuffixes = s : depSuffixes d
> }
>
>  addCmdlineFramework f d = d { cmdlineFrameworks = f : cmdlineFrameworks d}
>
> +addGhcVersion :: FilePath -> DynFlags -> DynFlags
> +addGhcVersion f d = d { ghcVersion = Just f }
> +
>  addHaddockOpts f d = d { haddockOptions = Just f}
>
>  addGhciScript f d = d { ghciScripts = f : ghciScripts d}
> @@ -2866,6 +2872,7 @@ dynamic_flags_deps = [
>    , make_ord_flag defGhcFlag "no-rtsopts-suggestions"
>        (noArg (\d -> d {rtsOptsSuggestions = False}))
>
> +  , make_ord_flag defGhcFlag "ghc-version"          (hasArg addGhcVersion)
>    , make_ord_flag defGhcFlag "main-is"              (SepArg setMainIs)
>    , make_ord_flag defGhcFlag "haddock"              (NoArg (setGeneralFlag
> Opt_Haddock))
>    , make_ord_flag defGhcFlag "haddock-opts"         (hasArg addHaddockOpts)
> diff --git a/docs/users_guide/using.rst b/docs/users_guide/using.rst
> index a963ead..e3fa741 100644
> --- a/docs/users_guide/using.rst
> +++ b/docs/users_guide/using.rst
> @@ -1064,3 +1064,26 @@ Some flags only make sense for particular target
> platforms.
>      and later). The :ref:`LLVM backend <llvm-code-gen>` will also use
>      SSE4.2 if your processor supports it but detects this automatically
>      so no flag is required.
> +
> +Miscellaneous flags
> +-------------------
> +
> +.. index::
> +   single: miscellaneous flags
> +
> +Some flags only make sense for a particular use case.
> +
> +.. ghc-flag:: -ghc-version ⟨path to ghcversion.h⟩
> +    :shortdesc: (GHC as a C compiler only) Use this ``ghcversion.h`` file
> +    :type: dynamic
> +    :category: misc
> +
> +    When GHC is used to compile C files, GHC adds package include paths and
> +    includes ``ghcversion.h`` directly. The compiler will lookup the path
> for
> +    the ``ghcversion.h`` file from the ``rts`` package in the package
> database.
> +    In some cases, the compiler's package database does not contain the
> ``rts``
> +    package, or one wants to specify a specific ``ghcversions.h`` to be
> +    included. This option can be used to specify the path to the
> +    ``ghcversions.h`` file to be included. This is primarily intended to be
> +    used by GHC's build system.
> +
>
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