[GHC] #8965: bootstrapping failure on Linux/ppc64el

[GHC]

#8965: bootstrapping failure on Linux/ppc64el
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        Reporter:  cjwatson                 |            Owner:
            Type:  bug                      |           Status:  patch
        Priority:  normal                   |        Milestone:  7.8.3
       Component:  Compiler                 |          Version:  7.8.1-rc2
      Resolution:                           |         Keywords:
Operating System:  Linux                    |     Architecture:  powerpc64
 Type of failure:  GHC doesn't work at all  |       Difficulty:  Unknown
       Test Case:                           |       Blocked By:
        Blocking:                           |  Related Tickets:
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Comment (by Austin Seipp <austin@…>):

 In [changeset:"5a31f231eebfb8140f9b519b166094d9d4fc2d79/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="5a31f231eebfb8140f9b519b166094d9d4fc2d79"
 Be less untruthful about the prototypes of external functions

 GHC's generated C code uses dummy prototypes for foreign imports.  At the
 moment these all claim to be (void), i.e. functions of zero arguments.  On
 most platforms this doesn't matter very much: calls to these functions put
 the parameters in the usual places anyway, and (with the exception of
 varargs) things just work.

 However, the ELFv2 ABI on ppc64 optimises stack allocation
 (http://gcc.gnu.org/ml/gcc-patches/2013-11/msg01149.html): a call to a
 function that has a prototype, is not varargs, and receives all parameters
 in registers rather than on the stack does not require the caller to
 allocate an argument save area.  The incorrect prototypes cause GCC to
 believe that all functions declared this way can be called without an
 argument save area, but if the callee has sufficiently many arguments then
 it will expect that area to be present, and will thus corrupt the caller's
 stack.  This happens in particular with calls to runInteractiveProcess in
 libraries/process/cbits/runProcess.c.

 The simplest fix appears to be to declare these external functions with an
 unspecified argument list rather than a void argument list.  This is no
 worse for platforms that don't care either way, and allows a successful
 bootstrap of GHC 7.8 on little-endian Linux ppc64 (which uses the ELFv2
 ABI).

 Fixes #8965

 Signed-off-by: Colin Watson <cjwatson at debian.org>
 Signed-off-by: Austin Seipp <austin at well-typed.com>
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8965#comment:7>
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