#2979: better support for FFI C wrappers for macros in system headers
------------------------------+---------------------------------------------
Reporter: duncan | Owner:
Type: feature request | Status: new
Priority: normal | Milestone: 7.4.1
Component: Compiler (FFI) | Version: 6.10.1
Resolution: | Keywords:
Testcase: | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
------------------------------+---------------------------------------------
Changes (by PHO):
* status: closed => new
* resolution: fixed =>
Comment:
Unfortunately, the brand-new {{{capi}}} calling convention doesn't work
well with macros that take pointers as their arguments.
From {{{libraries/base/System/Posix/Internals.hs}}}:
{{{
foreign import capi unsafe "HsBase.h sigaddset"
c_sigaddset :: Ptr CSigset -> CInt -> IO CInt
}}}
This foreign import generates the following C wrapper:
{{{
HsInt32 ghc_wrapper_d2kM_sigaddset(HsPtr a1, HsInt32 a2) {return
sigaddset(a1, a2);}
}}}
And yes, sigaddset(3) is actually defined as a macro (at least on Darwin
9.8.0):
{{{
#define sigaddset(set, signo) (*(set) |= __sigbits(signo), 0)
}}}
Since {{{HsPtr}}} is a type synonym of {{{void*}}} defined by
{{{includes/HsFFI.h}}}, the C wrapper in question end up dereferencing
{{{void*}}}:
{{{
/var/folders/rN/rNbpGijHEzGPi-Ux2JwMgU+++TI/-Tmp-/ghc27760_0/ghc27760_0.c:
In fu
nction ‘ghc_wrapper_d2kM_sigaddset’:
/var/folders/rN/rNbpGijHEzGPi-
Ux2JwMgU+++TI/-Tmp-/ghc27760_0/ghc27760_0.c:13:0:
warning: dereferencing ‘void *’ pointer
/var/folders/rN/rNbpGijHEzGPi-
Ux2JwMgU+++TI/-Tmp-/ghc27760_0/ghc27760_0.c:13:0:
error: invalid use of void expression
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2979#comment:14>
GHC <http://www.haskell.org/ghc/>
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