Re: [GHC] #11072: Runtime linker doesn't search for DLLs referenced in import libraries on Windows

17 Apr 2016

      #11072: Runtime linker doesn't search for DLLs referenced in import libraries on
Windows
-------------------------------------+-------------------------------------
        Reporter:  RyanGlScott       |                Owner:  Phyx-
            Type:  feature request   |               Status:  patch
        Priority:  normal            |            Milestone:  8.0.2
       Component:  Compiler          |              Version:  7.10.2-rc2
  (Linking)                          |
      Resolution:                    |             Keywords:
Operating System:  Windows           |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  Runtime crash     |            Test Case:  T11072gcc
                                     |  T11072msvc
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D1564
       Wiki Page:                    |  Phab:D1696
-------------------------------------+-------------------------------------

Comment (by Tamar Christina <tamar@…>):

 In [changeset:"97f2b16483aae28dc8fd60b6d2e1e283618f2390/ghc" 97f2b16/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="97f2b16483aae28dc8fd60b6d2e1e283618f2390"
 Add Windows import library support to the Runtime Linker

 Summary:
 Import libraries are files ending in `.dll.a` and `.lib` depending on
 which
 compiler creates them (GCC, vs MSVC).

 Import Libraries are standard `archive` files that contain object files.
 These object files can have two different formats:

 1) The normal COFF Object format for object files
     (contains all ascii data and very little program code, so do not
      try to execute.)
 2) "short import" format which just contains a symbol name and
    the dll in which the symbol can be found.

 Import Libraries are useful for two things:

 1) Allowing applications that don't support dynamic linking to
    link against the import lib (non-short format) which then
    makes calls into the DLL by loading it at runtime.

 2) Allow linking of mutually recursive dlls. if `A.DLL` requires
    `B.DLL` and vice versa, import libs can be used to break the cycle
    as they can be created from the expected exports of the DLLs.

 A side effect of having these two capabilities is that Import libs are
 often
 used to hide specific versions of DLLs behind a non-versioned import lib.

 e.g. GCC_S.a (non-conventional import lib) will point to the correct
 `libGCC` DLL. With this support Windows Haskell files can now just link
 to `-lGCC_S` and not have to worry about what the actual name of libGCC
 is.

 Also third party libraries such as `icuuc` use import libs to forward to
 versioned DLLs. e.g. `icuuc.lib` points to `icuuc51.dll` etc.

 Test Plan:
 ./validate

 Two new tests added T11072gcc T11072msvc

 Two binary files have been added to the test folder because the "short"
 import library format doesn't seem to be creatable via `dlltool`
 and requires Microsoft's `lib.exe`.

 Reviewers: bgamari, RyanGlScott, erikd, goldfire, austin, hvr

 Reviewed By: RyanGlScott, erikd

 Subscribers: thomie

 Differential Revision: https://phabricator.haskell.org/D1696

 GHC Trac Issues: #11072
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/11072#comment:20>
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