Merge pull request #2 from thomie/T8902

Add haddock comments on RTLD_NEXT and RTLD_DEFAULT

2 files changed, 26 insertions, 81 deletions

diff --git a/System/Posix/DynamicLinker/Prim.hsc b/System/Posix/DynamicLinker/Prim.hsc
index a111e3a..0bef60b 100644
--- a/System/Posix/DynamicLinker/Prim.hsc
+++ b/System/Posix/DynamicLinker/Prim.hsc
@@ -41,25 +41,22 @@ import Foreign.Ptr	( Ptr, FunPtr, nullPtr )
 import Foreign.C.Types
 import Foreign.C.String	( CString )
 
--- RTLD_NEXT madness
--- On some host (e.g. SuSe Linux 7.2) RTLD_NEXT is not visible
--- without setting _GNU_SOURCE. Since we don't want to set this
--- flag, here's a different solution: You can use the Haskell
--- function 'haveRtldNext' to check wether the flag is available
--- to you. Ideally, this will be optimized by the compiler so
--- that it should be as efficient as an #ifdef.
---    If you fail to test the flag and use it although it is
--- undefined, 'packOneModuleFlag' will bomb.
---    The same applies to RTLD_LOCAL which isn't available on
--- cygwin.
+
+-- |On some hosts (e.g. SuSe and Ubuntu Linux) 'RTLD_NEXT' (and
+-- 'RTLD_DEFAULT') are not visible without setting the macro
+-- '_GNU_SOURCE'. Since we don't want to define this macro, you can use
+-- the function 'haveRtldNext' to check wether the flag `Next` is
+-- available. Ideally, this will be optimized by the compiler so that it
+-- should be as efficient as an #ifdef.
+--
+-- If you fail to test the flag and use it although it is undefined,
+-- 'packDL' will throw an error.
 
 haveRtldNext :: Bool
 
 #ifdef HAVE_RTLDNEXT
 haveRtldNext = True
-
 foreign import ccall unsafe "__hsunix_rtldNext" rtldNext :: Ptr a
-
 #else  /* HAVE_RTLDNEXT */
 haveRtldNext = False
 #endif /* HAVE_RTLDNEXT */
@@ -69,12 +66,11 @@ foreign import ccall unsafe "__hsunix_rtldDefault" rtldDefault :: Ptr a
 #endif /* HAVE_RTLDDEFAULT */
 
 haveRtldLocal :: Bool
-
-#ifdef HAVE_RTLDLOCAL
 haveRtldLocal = True
-#else /* HAVE_RTLDLOCAL */
-haveRtldLocal = False
-#endif /* HAVE_RTLDLOCAL */
+{-# DEPRECATED haveRtldLocal "defaults to True" #-}
+
+
+-- |Flags for 'System.Posix.DynamicLinker.dlopen'.
 
 data RTLDFlags 
   = RTLD_LAZY
@@ -93,40 +89,33 @@ packRTLDFlags flags = foldl (\ s f -> (packRTLDFlag f) .|. s) 0 flags
 
 packRTLDFlag :: RTLDFlags -> CInt
 packRTLDFlag RTLD_LAZY = #const RTLD_LAZY
-
-#ifdef HAVE_RTLDNOW
 packRTLDFlag RTLD_NOW = #const RTLD_NOW
-#else /* HAVE_RTLDNOW */
-packRTLDFlag RTLD_NOW =  error "RTLD_NOW not available"
-#endif /* HAVE_RTLDNOW */
-
-#ifdef HAVE_RTLDGLOBAL
 packRTLDFlag RTLD_GLOBAL = #const RTLD_GLOBAL
-#else /* HAVE_RTLDGLOBAL */
-packRTLDFlag RTLD_GLOBAL = error "RTLD_GLOBAL not available"
-#endif
-
-#ifdef HAVE_RTLDLOCAL
 packRTLDFlag RTLD_LOCAL = #const RTLD_LOCAL
-#else /* HAVE_RTLDLOCAL */
-packRTLDFlag RTLD_LOCAL = error "RTLD_LOCAL not available"
-#endif /* HAVE_RTLDLOCAL */
+
 
 -- |Flags for 'System.Posix.DynamicLinker.dlsym'. Notice that 'Next'
--- might not be available on your particular platform!
+-- might not be available on your particular platform! Use
+-- `haveRtldNext`.
+--
+-- If 'RTLD_DEFAULT' is not defined on your platform, `packDL` `Default`
+-- reduces to 'nullPtr'.
 
 data DL = Null | Next | Default | DLHandle (Ptr ()) deriving (Show)
 
 packDL :: DL -> Ptr ()
 packDL Null = nullPtr
+
 #ifdef HAVE_RTLDNEXT
 packDL Next = rtldNext
 #else
 packDL Next = error "RTLD_NEXT not available"
 #endif
+
 #ifdef HAVE_RTLDDEFAULT
 packDL Default = rtldDefault
 #else
 packDL Default = nullPtr
 #endif
+
 packDL (DLHandle h) = h
diff --git a/configure.ac b/configure.ac
index f295061..41274dc 100644
--- a/configure.ac
+++ b/configure.ac
@@ -124,7 +124,9 @@ case "$fptools_cv_func_unsetenv_return_type" in
   ;;
 esac
 
-dnl ** sometimes RTLD_NEXT is hidden in #ifdefs we really don't wan to set
+dnl On some hosts (e.g. SuSe and Ubuntu Linux) RTLD_NEXT and RTLD_DEFAULT are
+dnl not visible without setting _GNU_SOURCE, which we really don't want to.
+dnl Also see comments in System/Posix/DynamicLinker/Prim.hsc.
 AC_MSG_CHECKING(for RTLD_NEXT from dlfcn.h)
 AC_EGREP_CPP(yes,
 [
@@ -139,7 +141,6 @@ AC_EGREP_CPP(yes,
   AC_MSG_RESULT(no)
   ])    
 
-dnl ** RTLD_DEFAULT isn't available on cygwin
 AC_MSG_CHECKING(for RTLD_DEFAULT from dlfcn.h)
 AC_EGREP_CPP(yes,
 [
@@ -154,51 +155,6 @@ AC_EGREP_CPP(yes,
   AC_MSG_RESULT(no)
   ])    
 
-dnl ** RTLD_LOCAL isn't available on cygwin or openbsd
-AC_MSG_CHECKING(for RTLD_LOCAL from dlfcn.h)
-AC_EGREP_CPP(yes,
-[
- #include <dlfcn.h>
- #ifdef RTLD_LOCAL
-        yes
- #endif
-], [
-  AC_MSG_RESULT(yes)
-  AC_DEFINE([HAVE_RTLDLOCAL], [1], [Define to 1 if RTLD_LOCAL is available.])
-], [
-  AC_MSG_RESULT(no)
-  ])    
-
-dnl ** RTLD_GLOBAL isn't available on openbsd
-AC_MSG_CHECKING(for RTLD_GLOBAL from dlfcn.h)
-AC_EGREP_CPP(yes,
-[
- #include <dlfcn.h>
- #ifdef RTLD_GLOBAL
-        yes
- #endif
-], [
-  AC_MSG_RESULT(yes)
-  AC_DEFINE([HAVE_RTLDGLOBAL], [1], [Define to 1 if RTLD_GLOBAL is available.])
-], [
-  AC_MSG_RESULT(no)
-  ])    
-
-dnl ** RTLD_NOW isn't available on openbsd
-AC_MSG_CHECKING(for RTLD_NOW from dlfcn.h)
-AC_EGREP_CPP(yes,
-[
- #include <dlfcn.h>
- #ifdef RTLD_NOW
-        yes
- #endif
-], [
-  AC_MSG_RESULT(yes)
-  AC_DEFINE([HAVE_RTLDNOW], [1], [Define to 1 if we can see RTLD_NOW in dlfcn.h])
-], [
-  AC_MSG_RESULT(no)
-  ])    
-
 AC_CHECK_FUNCS(openpty,,
    AC_CHECK_LIB(util,openpty,
      [AC_DEFINE(HAVE_OPENPTY) EXTRA_LIBS="$EXTRA_LIBS util"],