Move System.Posix.Signals from base

Also adds System.Posix.Process.Internals in order to make the deps work out.

6 files changed, 749 insertions, 6 deletions

diff --git a/System/Posix/Process.hsc b/System/Posix/Process.hsc
index 9962d94..a6bbaa1 100644
--- a/System/Posix/Process.hsc
+++ b/System/Posix/Process.hsc
@@ -74,9 +74,9 @@ import System.IO
 import System.IO.Error
 import System.Exit
 import System.Posix.Error
+import System.Posix.Process.Internals ( pPrPr_disableITimers, c_execvpe )
 import System.Posix.Types
 import System.Posix.Signals
-import System.Process.Internals ( pPrPr_disableITimers, c_execvpe )
 import Control.Monad
 
 #ifdef __GLASGOW_HASKELL__
diff --git a/System/Posix/Process/Internals.hs b/System/Posix/Process/Internals.hs
new file mode 100644
index 0000000..8639819
--- /dev/null
+++ b/System/Posix/Process/Internals.hs
@@ -0,0 +1,13 @@
+
+module System.Posix.Process.Internals (pPrPr_disableITimers, c_execvpe) where
+
+import Foreign
+import Foreign.C
+
+-- this function disables the itimer, which would otherwise cause confusing
+-- signals to be sent to the new process.
+foreign import ccall unsafe "pPrPr_disableITimers"
+  pPrPr_disableITimers :: IO ()
+
+foreign import ccall unsafe "execvpe"
+  c_execvpe :: CString -> Ptr CString -> Ptr CString -> IO CInt
diff --git a/System/Posix/Signals.hs b/System/Posix/Signals.hs
new file mode 100644
index 0000000..1aa9dca
--- /dev/null
+++ b/System/Posix/Signals.hs
@@ -0,0 +1,528 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  System.Posix.Signals
+-- Copyright   :  (c) The University of Glasgow 2002
+-- License     :  BSD-style (see the file libraries/base/LICENSE)
+-- 
+-- Maintainer  :  libraries@haskell.org
+-- Stability   :  provisional
+-- Portability :  non-portable (requires POSIX)
+--
+-- POSIX signal support
+--
+-----------------------------------------------------------------------------
+
+#include "HsBaseConfig.h"
+
+module System.Posix.Signals (
+  -- * The Signal type
+  Signal,
+
+  -- * Specific signals
+  nullSignal,
+  internalAbort, sigABRT,
+  realTimeAlarm, sigALRM,
+  busError, sigBUS,
+  processStatusChanged, sigCHLD,
+  continueProcess, sigCONT,
+  floatingPointException, sigFPE,
+  lostConnection, sigHUP,
+  illegalInstruction, sigILL,
+  keyboardSignal, sigINT,
+  killProcess, sigKILL,
+  openEndedPipe, sigPIPE,
+  keyboardTermination, sigQUIT,
+  segmentationViolation, sigSEGV,
+  softwareStop, sigSTOP,
+  softwareTermination, sigTERM,
+  keyboardStop, sigTSTP,
+  backgroundRead, sigTTIN,
+  backgroundWrite, sigTTOU,
+  userDefinedSignal1, sigUSR1,
+  userDefinedSignal2, sigUSR2,
+#if CONST_SIGPOLL != -1
+  pollableEvent, sigPOLL,
+#endif
+  profilingTimerExpired, sigPROF,
+  badSystemCall, sigSYS,
+  breakpointTrap, sigTRAP,
+  urgentDataAvailable, sigURG,
+  virtualTimerExpired, sigVTALRM,
+  cpuTimeLimitExceeded, sigXCPU,
+  fileSizeLimitExceeded, sigXFSZ,
+
+  -- * Sending signals
+  raiseSignal,
+  signalProcess,
+  signalProcessGroup,
+
+#ifdef __GLASGOW_HASKELL__
+  -- * Handling signals
+  Handler(..),
+  installHandler,
+#endif
+
+  -- * Signal sets
+  SignalSet,
+  emptySignalSet, fullSignalSet, 
+  addSignal, deleteSignal, inSignalSet,
+
+  -- * The process signal mask
+  getSignalMask, setSignalMask, blockSignals, unblockSignals,
+
+  -- * The alarm timer
+  scheduleAlarm,
+
+  -- * Waiting for signals
+  getPendingSignals,
+#ifndef cygwin32_HOST_OS
+  awaitSignal,
+#endif
+
+#ifdef __GLASGOW_HASKELL__
+  -- * The @NOCLDSTOP@ flag
+  setStoppedChildFlag, queryStoppedChildFlag,
+#endif
+
+  -- MISSING FUNCTIONALITY:
+  -- sigaction(), (inc. the sigaction structure + flags etc.)
+  -- the siginfo structure
+  -- sigaltstack()
+  -- sighold, sigignore, sigpause, sigrelse, sigset
+  -- siginterrupt
+  ) where
+
+import Foreign
+import Foreign.C
+import System.IO.Unsafe
+import System.Posix.Types
+import System.Posix.Internals
+
+#ifdef __GLASGOW_HASKELL__
+#include "Signals.h"
+import GHC.Conc	( ensureIOManagerIsRunning )
+#endif
+
+-- -----------------------------------------------------------------------------
+-- Specific signals
+
+type Signal = CInt
+
+nullSignal :: Signal
+nullSignal = 0
+
+sigABRT   :: CInt
+sigABRT   = CONST_SIGABRT
+sigALRM   :: CInt
+sigALRM   = CONST_SIGALRM
+sigBUS    :: CInt
+sigBUS    = CONST_SIGBUS
+sigCHLD   :: CInt
+sigCHLD   = CONST_SIGCHLD
+sigCONT   :: CInt
+sigCONT   = CONST_SIGCONT
+sigFPE    :: CInt
+sigFPE    = CONST_SIGFPE
+sigHUP    :: CInt
+sigHUP    = CONST_SIGHUP
+sigILL    :: CInt
+sigILL    = CONST_SIGILL
+sigINT    :: CInt
+sigINT    = CONST_SIGINT
+sigKILL   :: CInt
+sigKILL   = CONST_SIGKILL
+sigPIPE   :: CInt
+sigPIPE   = CONST_SIGPIPE
+sigQUIT   :: CInt
+sigQUIT   = CONST_SIGQUIT
+sigSEGV   :: CInt
+sigSEGV   = CONST_SIGSEGV
+sigSTOP   :: CInt
+sigSTOP   = CONST_SIGSTOP
+sigTERM   :: CInt
+sigTERM   = CONST_SIGTERM
+sigTSTP   :: CInt
+sigTSTP   = CONST_SIGTSTP
+sigTTIN   :: CInt
+sigTTIN   = CONST_SIGTTIN
+sigTTOU   :: CInt
+sigTTOU   = CONST_SIGTTOU
+sigUSR1   :: CInt
+sigUSR1   = CONST_SIGUSR1
+sigUSR2   :: CInt
+sigUSR2   = CONST_SIGUSR2
+sigPOLL   :: CInt
+sigPOLL   = CONST_SIGPOLL
+sigPROF   :: CInt
+sigPROF   = CONST_SIGPROF
+sigSYS    :: CInt
+sigSYS    = CONST_SIGSYS
+sigTRAP   :: CInt
+sigTRAP   = CONST_SIGTRAP
+sigURG    :: CInt
+sigURG    = CONST_SIGURG
+sigVTALRM :: CInt
+sigVTALRM = CONST_SIGVTALRM
+sigXCPU   :: CInt
+sigXCPU   = CONST_SIGXCPU
+sigXFSZ   :: CInt
+sigXFSZ   = CONST_SIGXFSZ
+
+internalAbort ::Signal
+internalAbort = sigABRT
+
+realTimeAlarm :: Signal
+realTimeAlarm = sigALRM
+
+busError :: Signal
+busError = sigBUS
+
+processStatusChanged :: Signal
+processStatusChanged = sigCHLD
+
+continueProcess :: Signal
+continueProcess = sigCONT
+
+floatingPointException :: Signal
+floatingPointException = sigFPE
+
+lostConnection :: Signal
+lostConnection = sigHUP
+
+illegalInstruction :: Signal
+illegalInstruction = sigILL
+
+keyboardSignal :: Signal
+keyboardSignal = sigINT
+
+killProcess :: Signal
+killProcess = sigKILL
+
+openEndedPipe :: Signal
+openEndedPipe = sigPIPE
+
+keyboardTermination :: Signal
+keyboardTermination = sigQUIT
+
+segmentationViolation :: Signal
+segmentationViolation = sigSEGV
+
+softwareStop :: Signal
+softwareStop = sigSTOP
+
+softwareTermination :: Signal
+softwareTermination = sigTERM
+
+keyboardStop :: Signal
+keyboardStop = sigTSTP
+
+backgroundRead :: Signal
+backgroundRead = sigTTIN
+
+backgroundWrite :: Signal
+backgroundWrite = sigTTOU
+
+userDefinedSignal1 :: Signal
+userDefinedSignal1 = sigUSR1
+
+userDefinedSignal2 :: Signal
+userDefinedSignal2 = sigUSR2
+
+#if CONST_SIGPOLL != -1
+pollableEvent :: Signal
+pollableEvent = sigPOLL
+#endif
+
+profilingTimerExpired :: Signal
+profilingTimerExpired = sigPROF
+
+badSystemCall :: Signal
+badSystemCall = sigSYS
+
+breakpointTrap :: Signal
+breakpointTrap = sigTRAP
+
+urgentDataAvailable :: Signal
+urgentDataAvailable = sigURG
+
+virtualTimerExpired :: Signal
+virtualTimerExpired = sigVTALRM
+
+cpuTimeLimitExceeded :: Signal
+cpuTimeLimitExceeded = sigXCPU
+
+fileSizeLimitExceeded :: Signal
+fileSizeLimitExceeded = sigXFSZ
+
+-- -----------------------------------------------------------------------------
+-- Signal-related functions
+
+-- | @signalProcess int pid@ calls @kill@ to signal process @pid@ 
+--   with interrupt signal @int@.
+signalProcess :: Signal -> ProcessID -> IO ()
+signalProcess sig pid 
+ = throwErrnoIfMinus1_ "signalProcess" (c_kill (fromIntegral pid) sig)
+
+foreign import ccall unsafe "kill"
+  c_kill :: CPid -> CInt -> IO CInt
+
+
+-- | @signalProcessGroup int pgid@ calls @kill@ to signal 
+--  all processes in group @pgid@ with interrupt signal @int@.
+signalProcessGroup :: Signal -> ProcessGroupID -> IO ()
+signalProcessGroup sig pgid 
+  = throwErrnoIfMinus1_ "signalProcessGroup" (c_killpg (fromIntegral pgid) sig)
+
+foreign import ccall unsafe "killpg"
+  c_killpg :: CPid -> CInt -> IO CInt
+
+-- | @raiseSignal int@ calls @kill@ to signal the current process
+--   with interrupt signal @int@. 
+raiseSignal :: Signal -> IO ()
+raiseSignal sig = throwErrnoIfMinus1_ "raiseSignal" (c_raise sig)
+
+#if defined(__GLASGOW_HASKELL__) && (defined(openbsd_HOST_OS) || defined(freebsd_HOST_OS))
+foreign import ccall unsafe "genericRaise"
+  c_raise :: CInt -> IO CInt
+#else
+foreign import ccall unsafe "raise"
+  c_raise :: CInt -> IO CInt
+#endif
+
+#ifdef __GLASGOW_HASKELL__
+data Handler = Default
+             | Ignore
+	     -- not yet: | Hold 
+             | Catch (IO ())
+             | CatchOnce (IO ())
+
+-- | @installHandler int handler iset@ calls @sigaction@ to install an
+--   interrupt handler for signal @int@.  If @handler@ is @Default@,
+--   @SIG_DFL@ is installed; if @handler@ is @Ignore@, @SIG_IGN@ is
+--   installed; if @handler@ is @Catch action@, a handler is installed
+--   which will invoke @action@ in a new thread when (or shortly after) the
+--   signal is received.
+--   If @iset@ is @Just s@, then the @sa_mask@ of the @sigaction@ structure
+--   is set to @s@; otherwise it is cleared.  The previously installed
+--   signal handler for @int@ is returned
+installHandler :: Signal
+               -> Handler
+               -> Maybe SignalSet	-- ^ other signals to block
+               -> IO Handler		-- ^ old handler
+
+#ifdef __PARALLEL_HASKELL__
+installHandler = 
+  error "installHandler: not available for Parallel Haskell"
+#else
+
+installHandler int handler maybe_mask = do
+    ensureIOManagerIsRunning  -- for the threaded RTS
+    case maybe_mask of
+	Nothing -> install' nullPtr
+        Just (SignalSet x) -> withForeignPtr x $ install' 
+  where 
+    install' mask = 
+      alloca $ \p_sp -> do
+
+      rc <- case handler of
+      	      Default      -> stg_sig_install int STG_SIG_DFL p_sp mask
+      	      Ignore       -> stg_sig_install int STG_SIG_IGN p_sp mask
+      	      Catch m      -> hinstall m p_sp mask int STG_SIG_HAN
+      	      CatchOnce m  -> hinstall m p_sp mask int STG_SIG_RST
+
+      case rc of
+	STG_SIG_DFL -> return Default
+	STG_SIG_IGN -> return Ignore
+	STG_SIG_ERR -> throwErrno "installHandler"
+	STG_SIG_HAN -> do
+        	m <- peekHandler p_sp
+		return (Catch m)
+	STG_SIG_RST -> do
+        	m <- peekHandler p_sp
+		return (CatchOnce m)
+	_other ->
+	   error "internal error: System.Posix.Signals.installHandler"
+
+    hinstall m p_sp mask int reset = do
+      sptr <- newStablePtr m
+      poke p_sp sptr
+      stg_sig_install int reset p_sp mask
+
+    peekHandler p_sp = do
+      osptr <- peek p_sp
+      deRefStablePtr osptr
+
+foreign import ccall unsafe
+  stg_sig_install
+	:: CInt				-- sig no.
+	-> CInt				-- action code (STG_SIG_HAN etc.)
+	-> Ptr (StablePtr (IO ()))	-- (in, out) Haskell handler
+	-> Ptr CSigset			-- (in, out) blocked
+	-> IO CInt			-- (ret) action code
+
+#endif /* !__PARALLEL_HASKELL__ */
+#endif /* __GLASGOW_HASKELL__ */
+
+-- -----------------------------------------------------------------------------
+-- Alarms
+
+-- | @scheduleAlarm i@ calls @alarm@ to schedule a real time
+--   alarm at least @i@ seconds in the future.
+scheduleAlarm :: Int -> IO Int
+scheduleAlarm secs = do
+   r <- c_alarm (fromIntegral secs)
+   return (fromIntegral r)
+
+foreign import ccall unsafe "alarm"
+  c_alarm :: CUInt -> IO CUInt
+
+#ifdef __GLASGOW_HASKELL__
+-- -----------------------------------------------------------------------------
+-- The NOCLDSTOP flag
+
+foreign import ccall "&nocldstop" nocldstop :: Ptr Int
+
+-- | Tells the system whether or not to set the @SA_NOCLDSTOP@ flag when
+-- installing new signal handlers.
+setStoppedChildFlag :: Bool -> IO Bool
+setStoppedChildFlag b = do
+    rc <- peek nocldstop
+    poke nocldstop $ fromEnum (not b) 
+    return (rc == (0::Int))
+
+-- | Queries the current state of the stopped child flag.
+queryStoppedChildFlag :: IO Bool
+queryStoppedChildFlag = do
+    rc <- peek nocldstop
+    return (rc == (0::Int))
+#endif /* __GLASGOW_HASKELL__ */
+
+-- -----------------------------------------------------------------------------
+-- Manipulating signal sets
+
+newtype SignalSet = SignalSet (ForeignPtr CSigset)
+
+emptySignalSet :: SignalSet
+emptySignalSet = unsafePerformIO $ do
+  fp <- mallocForeignPtrBytes sizeof_sigset_t
+  throwErrnoIfMinus1_ "emptySignalSet" (withForeignPtr fp $ c_sigemptyset)
+  return (SignalSet fp)
+
+fullSignalSet :: SignalSet
+fullSignalSet = unsafePerformIO $ do
+  fp <- mallocForeignPtrBytes sizeof_sigset_t
+  throwErrnoIfMinus1_ "fullSignalSet" (withForeignPtr fp $ c_sigfillset)
+  return (SignalSet fp)
+
+infixr `addSignal`, `deleteSignal`
+addSignal :: Signal -> SignalSet -> SignalSet
+addSignal sig (SignalSet fp1) = unsafePerformIO $ do
+  fp2 <- mallocForeignPtrBytes sizeof_sigset_t
+  withForeignPtr fp1 $ \p1 ->
+    withForeignPtr fp2 $ \p2 -> do
+      copyBytes p2 p1 sizeof_sigset_t
+      throwErrnoIfMinus1_ "addSignal" (c_sigaddset p2 sig)
+  return (SignalSet fp2)
+
+deleteSignal :: Signal -> SignalSet -> SignalSet
+deleteSignal sig (SignalSet fp1) = unsafePerformIO $ do
+  fp2 <- mallocForeignPtrBytes sizeof_sigset_t
+  withForeignPtr fp1 $ \p1 ->
+    withForeignPtr fp2 $ \p2 -> do
+      copyBytes p2 p1 sizeof_sigset_t
+      throwErrnoIfMinus1_ "deleteSignal" (c_sigdelset p2 sig)
+  return (SignalSet fp2)
+
+inSignalSet :: Signal -> SignalSet -> Bool
+inSignalSet sig (SignalSet fp) = unsafePerformIO $
+  withForeignPtr fp $ \p -> do
+    r <- throwErrnoIfMinus1 "inSignalSet" (c_sigismember p sig)
+    return (r /= 0)
+
+-- | @getSignalMask@ calls @sigprocmask@ to determine the
+--   set of interrupts which are currently being blocked.
+getSignalMask :: IO SignalSet
+getSignalMask = do
+  fp <- mallocForeignPtrBytes sizeof_sigset_t
+  withForeignPtr fp $ \p ->
+    throwErrnoIfMinus1_ "getSignalMask" (c_sigprocmask 0 nullPtr p)
+  return (SignalSet fp)
+   
+sigProcMask :: String -> CInt -> SignalSet -> IO ()
+sigProcMask fn how (SignalSet set) =
+  withForeignPtr set $ \p_set ->
+    throwErrnoIfMinus1_ fn (c_sigprocmask how p_set nullPtr)
+
+-- | @setSignalMask mask@ calls @sigprocmask@ with
+--   @SIG_SETMASK@ to block all interrupts in @mask@.
+setSignalMask :: SignalSet -> IO ()
+setSignalMask set = sigProcMask "setSignalMask" (CONST_SIG_SETMASK :: CInt) set
+
+-- | @blockSignals mask@ calls @sigprocmask@ with
+--   @SIG_BLOCK@ to add all interrupts in @mask@ to the
+--  set of blocked interrupts.
+blockSignals :: SignalSet -> IO ()
+blockSignals set = sigProcMask "blockSignals" (CONST_SIG_BLOCK :: CInt) set
+
+-- | @unblockSignals mask@ calls @sigprocmask@ with
+--   @SIG_UNBLOCK@ to remove all interrupts in @mask@ from the
+--   set of blocked interrupts. 
+unblockSignals :: SignalSet -> IO ()
+unblockSignals set = sigProcMask "unblockSignals" (CONST_SIG_UNBLOCK :: CInt) set
+
+-- | @getPendingSignals@ calls @sigpending@ to obtain
+--   the set of interrupts which have been received but are currently blocked.
+getPendingSignals :: IO SignalSet
+getPendingSignals = do
+  fp <- mallocForeignPtrBytes sizeof_sigset_t
+  withForeignPtr fp $ \p -> 
+   throwErrnoIfMinus1_ "getPendingSignals" (c_sigpending p)
+  return (SignalSet fp)
+
+#ifndef cygwin32_HOST_OS
+
+-- | @awaitSignal iset@ suspends execution until an interrupt is received.
+-- If @iset@ is @Just s@, @awaitSignal@ calls @sigsuspend@, installing
+-- @s@ as the new signal mask before suspending execution; otherwise, it
+-- calls @pause@.  @awaitSignal@ returns on receipt of a signal.  If you
+-- have installed any signal handlers with @installHandler@, it may be
+-- wise to call @yield@ directly after @awaitSignal@ to ensure that the
+-- signal handler runs as promptly as possible.
+awaitSignal :: Maybe SignalSet -> IO ()
+awaitSignal maybe_sigset = do
+  fp <- case maybe_sigset of
+    	  Nothing -> do SignalSet fp <- getSignalMask; return fp
+    	  Just (SignalSet fp) -> return fp
+  withForeignPtr fp $ \p -> do
+  c_sigsuspend p
+  return ()
+  -- ignore the return value; according to the docs it can only ever be
+  -- (-1) with errno set to EINTR.
+ 
+foreign import ccall unsafe "sigsuspend"
+  c_sigsuspend :: Ptr CSigset -> IO CInt
+#endif
+
+#ifdef __HUGS__
+foreign import ccall unsafe "sigdelset"
+  c_sigdelset   :: Ptr CSigset -> CInt -> IO CInt
+
+foreign import ccall unsafe "sigfillset"
+  c_sigfillset  :: Ptr CSigset -> IO CInt
+
+foreign import ccall unsafe "sigismember"
+  c_sigismember :: Ptr CSigset -> CInt -> IO CInt
+#else
+foreign import ccall unsafe "__hscore_sigdelset"
+  c_sigdelset   :: Ptr CSigset -> CInt -> IO CInt
+
+foreign import ccall unsafe "__hscore_sigfillset"
+  c_sigfillset  :: Ptr CSigset -> IO CInt
+
+foreign import ccall unsafe "__hscore_sigismember"
+  c_sigismember :: Ptr CSigset -> CInt -> IO CInt
+#endif /* __HUGS__ */
+
+foreign import ccall unsafe "sigpending"
+  c_sigpending :: Ptr CSigset -> IO CInt
+
diff --git a/cbits/execvpe.c b/cbits/execvpe.c
new file mode 100644
index 0000000..160271c
--- /dev/null
+++ b/cbits/execvpe.c
@@ -0,0 +1,175 @@
+/* -----------------------------------------------------------------------------
+   (c) The University of Glasgow 1995-2004
+
+   Our low-level exec() variant.
+   -------------------------------------------------------------------------- */
+#include "execvpe.h"
+
+#if !(defined(_MSC_VER) || defined(__MINGW32__) || defined(_WIN32)) /* to the end */
+
+/* Evidently non-Posix. */
+/* #include "PosixSource.h" */
+
+#include <unistd.h>
+#include <sys/time.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+/*
+ * We want the search semantics of execvp, but we want to provide our
+ * own environment, like execve.  The following copyright applies to
+ * this code, as it is a derivative of execvp:
+ *-
+ * Copyright (c) 1991 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+int
+execvpe(char *name, char *const argv[], char **envp)
+{
+    register int lp, ln;
+    register char *p;
+    int eacces=0, etxtbsy=0;
+    char *bp, *cur, *path, *buf = 0;
+
+    /* If it's an absolute or relative path name, it's easy. */
+    if (strchr(name, '/')) {
+	bp = (char *) name;
+	cur = path = buf = NULL;
+	goto retry;
+    }
+
+    /* Get the path we're searching. */
+    if (!(path = getenv("PATH"))) {
+#ifdef HAVE_CONFSTR
+        ln = confstr(_CS_PATH, NULL, 0);
+        if ((cur = path = malloc(ln + 1)) != NULL) {
+	    path[0] = ':';
+	    (void) confstr (_CS_PATH, path + 1, ln);
+	}
+#else
+        if ((cur = path = malloc(1 + 1)) != NULL) {
+	    path[0] = ':';
+	    path[1] = '\0';
+	}
+#endif
+    } else
+	cur = path = strdup(path);
+
+    if (path == NULL || (bp = buf = malloc(strlen(path)+strlen(name)+2)) == NULL)
+	goto done;
+
+    while (cur != NULL) {
+	p = cur;
+        if ((cur = strchr(cur, ':')) != NULL)
+	    *cur++ = '\0';
+
+	/*
+	 * It's a SHELL path -- double, leading and trailing colons mean the current
+	 * directory.
+	 */
+	if (!*p) {
+	    p = ".";
+	    lp = 1;
+	} else
+	    lp = strlen(p);
+	ln = strlen(name);
+
+	memcpy(buf, p, lp);
+	buf[lp] = '/';
+	memcpy(buf + lp + 1, name, ln);
+	buf[lp + ln + 1] = '\0';
+
+      retry:
+        (void) execve(bp, argv, envp);
+	switch (errno) {
+	case EACCES:
+	    eacces = 1;
+	    break;
+	case ENOENT:
+	    break;
+	case ENOEXEC:
+	    {
+		register size_t cnt;
+		register char **ap;
+
+		for (cnt = 0, ap = (char **) argv; *ap; ++ap, ++cnt)
+		    ;
+		if ((ap = malloc((cnt + 2) * sizeof(char *))) != NULL) {
+		    memcpy(ap + 2, argv + 1, cnt * sizeof(char *));
+
+		    ap[0] = "sh";
+		    ap[1] = bp;
+		    (void) execve("/bin/sh", ap, envp);
+		    free(ap);
+		}
+		goto done;
+	    }
+	case ETXTBSY:
+	    if (etxtbsy < 3)
+		(void) sleep(++etxtbsy);
+	    goto retry;
+	default:
+	    goto done;
+	}
+    }
+    if (eacces)
+	errno = EACCES;
+    else if (!errno)
+	errno = ENOENT;
+  done:
+    if (path)
+	free(path);
+    if (buf)
+	free(buf);
+    return (-1);
+}
+
+
+/* Copied verbatim from ghc/lib/std/cbits/system.c. */
+void pPrPr_disableITimers (void)
+{
+#  ifdef HAVE_SETITIMER
+   /* Reset the itimers in the child, so it doesn't get plagued
+    * by SIGVTALRM interrupts.
+    */
+   struct timeval tv_null = { 0, 0 };
+   struct itimerval itv;
+   itv.it_interval = tv_null;
+   itv.it_value = tv_null;
+   setitimer(ITIMER_REAL, &itv, NULL);
+   setitimer(ITIMER_VIRTUAL, &itv, NULL);
+   setitimer(ITIMER_PROF, &itv, NULL);
+#  endif
+}
+
+#endif
diff --git a/include/execvpe.h b/include/execvpe.h
new file mode 100644
index 0000000..676fc72
--- /dev/null
+++ b/include/execvpe.h
@@ -0,0 +1,25 @@
+/* ----------------------------------------------------------------------------
+   (c) The University of Glasgow 2004
+
+   Interface for code in execvpe.c
+   ------------------------------------------------------------------------- */
+
+#include "HsUnixConfig.h"
+// Otherwise these clash with similar definitions from other packages:
+#undef PACKAGE_BUGREPORT
+#undef PACKAGE_NAME
+#undef PACKAGE_STRING
+#undef PACKAGE_TARNAME
+#undef PACKAGE_VERSION
+
+#include <errno.h>
+#include <sys/types.h>
+#if HAVE_SYS_WAIT_H
+#include <sys/wait.h>
+#endif
+
+#if !defined(_MSC_VER) && !defined(__MINGW32__) && !defined(_WIN32)
+extern int execvpe(char *name, char *const argv[], char **envp);
+extern void pPrPr_disableITimers (void);
+#endif
+
diff --git a/unix.cabal b/unix.cabal
index 9f2267b..9f2cc8e 100644
--- a/unix.cabal
+++ b/unix.cabal
@@ -22,12 +22,14 @@ exposed-modules:
 		System.Posix.Files
 		System.Posix.IO
 		System.Posix.Process
+		System.Posix.Process.Internals
 		System.Posix.Resource
 		System.Posix.Temp
 		System.Posix.Terminal
 		System.Posix.Time
 		System.Posix.Unistd
 		System.Posix.User
+        System.Posix.Signals
 		System.Posix.Signals.Exts
                 System.Posix.Semaphore
                 System.Posix.SharedMem
@@ -38,10 +40,10 @@ extra-source-files:
 extra-tmp-files:
 		config.log config.status autom4te.cache
 		unix.buildinfo include/HsUnixConfig.h
-build-depends:	base, directory, process
-extensions:	CPP
+build-depends:	base, directory
+extensions:	CPP, ForeignFunctionInterface
 include-dirs: 	include
-includes:       HsUnix.h
+includes:       HsUnix.h execvpe.h
 install-includes:
-		HsUnix.h HsUnixConfig.h
-c-sources:	cbits/HsUnix.c
+		HsUnix.h HsUnixConfig.h execvpe.h
+c-sources:	cbits/HsUnix.c cbits/execvpe.c