Don't assume `tcdrain` and `ctermid` exist always

This follows the scheme suggested in #24

This fixes #55

5 files changed, 64 insertions, 4 deletions

diff --git a/System/Posix/Terminal.hsc b/System/Posix/Terminal.hsc
index c8335a6..88bd93f 100644
--- a/System/Posix/Terminal.hsc
+++ b/System/Posix/Terminal.hsc
@@ -1,3 +1,4 @@
+{-# LANGUAGE CApiFFI #-}
 #if __GLASGOW_HASKELL__ >= 709
 {-# LANGUAGE Safe #-}
 #elif __GLASGOW_HASKELL__ >= 703
@@ -83,6 +84,11 @@ import System.Posix.IO
 
 import System.Posix.Internals (peekFilePath)
 
+#if !HAVE_CTERMID
+import System.IO.Error ( ioeSetLocation )
+import GHC.IO.Exception ( unsupportedOperation )
+#endif
+
 -- | @getTerminalName fd@ calls @ttyname@ to obtain a name associated
 --   with the terminal for @Fd@ @fd@. If @fd@ is associated
 --   with a terminal, @getTerminalName@ returns the name of the
@@ -100,13 +106,23 @@ foreign import ccall unsafe "ttyname"
 --   controlling terminal exists,
 --   @getControllingTerminalName@ returns the name of the
 --   controlling terminal.
+--
+-- Throws 'IOError' (\"unsupported operation\") if platform does not
+-- provide @ctermid(3)@ (use @#if HAVE_CTERMID@ CPP guard to
+-- detect availability).
 getControllingTerminalName :: IO FilePath
+#if HAVE_CTERMID
 getControllingTerminalName = do
   s <- throwErrnoIfNull "getControllingTerminalName" (c_ctermid nullPtr)
   peekFilePath s
 
-foreign import ccall unsafe "ctermid"
+foreign import capi unsafe "termios.h ctermid"
   c_ctermid :: CString -> IO CString
+#else
+{-# WARNING getControllingTerminalName
+    "operation will throw 'IOError' \"unsupported operation\" (CPP guard: @#if HAVE_CTERMID@)" #-}
+getControllingTerminalName = ioError (ioeSetLocation unsupportedOperation "getControllingTerminalName")
+#endif
 
 -- | @getSlaveTerminalName@ calls @ptsname@ to obtain the name of the
 -- slave terminal associated with a pseudoterminal pair.  The file
diff --git a/System/Posix/Terminal/ByteString.hsc b/System/Posix/Terminal/ByteString.hsc
index fd44c85..3c7abfb 100644
--- a/System/Posix/Terminal/ByteString.hsc
+++ b/System/Posix/Terminal/ByteString.hsc
@@ -1,3 +1,4 @@
+{-# LANGUAGE CApiFFI #-}
 #if __GLASGOW_HASKELL__ >= 709
 {-# LANGUAGE Safe #-}
 #elif __GLASGOW_HASKELL__ >= 703
@@ -91,6 +92,10 @@ import Foreign.C hiding (
 
 import System.Posix.ByteString.FilePath
 
+#if !HAVE_CTERMID
+import System.IO.Error ( ioeSetLocation )
+import GHC.IO.Exception ( unsupportedOperation )
+#endif
 
 -- | @getTerminalName fd@ calls @ttyname@ to obtain a name associated
 --   with the terminal for @Fd@ @fd@. If @fd@ is associated
@@ -109,13 +114,23 @@ foreign import ccall unsafe "ttyname"
 --   controlling terminal exists,
 --   @getControllingTerminalName@ returns the name of the
 --   controlling terminal.
+--
+-- Throws 'IOError' (\"unsupported operation\") if platform does not
+-- provide @ctermid(3)@ (use @#if HAVE_CTERMID@ CPP guard to
+-- detect availability).
 getControllingTerminalName :: IO RawFilePath
+#if HAVE_CTERMID
 getControllingTerminalName = do
   s <- throwErrnoIfNull "getControllingTerminalName" (c_ctermid nullPtr)
   peekFilePath s
 
-foreign import ccall unsafe "ctermid"
+foreign import capi unsafe "termios.h ctermid"
   c_ctermid :: CString -> IO CString
+#else
+{-# WARNING getControllingTerminalName
+    "operation will throw 'IOError' \"unsupported operation\" (CPP guard: @#if HAVE_CTERMID@)" #-}
+getControllingTerminalName = ioError (ioeSetLocation unsupportedOperation "getControllingTerminalName")
+#endif
 
 -- | @getSlaveTerminalName@ calls @ptsname@ to obtain the name of the
 -- slave terminal associated with a pseudoterminal pair.  The file
diff --git a/System/Posix/Terminal/Common.hsc b/System/Posix/Terminal/Common.hsc
index 49418f5..4825b10 100644
--- a/System/Posix/Terminal/Common.hsc
+++ b/System/Posix/Terminal/Common.hsc
@@ -78,6 +78,11 @@ import Foreign.Storable ( Storable(..) )
 import System.IO.Unsafe ( unsafePerformIO )
 import System.Posix.Types
 
+#if !HAVE_TCDRAIN
+import System.IO.Error ( ioeSetLocation )
+import GHC.IO.Exception ( unsupportedOperation )
+#endif
+
 -- -----------------------------------------------------------------------------
 -- Terminal attributes
 
@@ -408,12 +413,21 @@ foreign import capi unsafe "termios.h tcsendbreak"
 
 -- | @drainOutput fd@ calls @tcdrain@ to block until all output
 --   written to @Fd@ @fd@ has been transmitted.
+--
+-- Throws 'IOError' (\"unsupported operation\") if platform does not
+-- provide @tcdrain(3)@ (use @#if HAVE_TCDRAIN@ CPP guard to
+-- detect availability).
 drainOutput :: Fd -> IO ()
+#if HAVE_TCDRAIN
 drainOutput (Fd fd) = throwErrnoIfMinus1_ "drainOutput" (c_tcdrain fd)
 
 foreign import capi unsafe "termios.h tcdrain"
   c_tcdrain :: CInt -> IO CInt
-
+#else
+{-# WARNING drainOutput
+    "operation will throw 'IOError' \"unsupported operation\" (CPP guard: @#if HAVE_TCDRAIN@)" #-}
+drainOutput _ = ioError (ioeSetLocation unsupportedOperation "drainOutput")
+#endif
 
 data QueueSelector
   = InputQueue          -- TCIFLUSH
diff --git a/changelog.md b/changelog.md
index e9c4ece..c6d6b69 100644
--- a/changelog.md
+++ b/changelog.md
@@ -4,7 +4,9 @@
 
   * Don't assume non-POSIX `WCOREDUMP(x)` macro exists
 
-  * Don't assume existence of termios constants beyond `B38400`
+  * Don't assume existence of `termios(3)` constants beyond `B38400`
+
+  * Don't assume existence of `ctermid(3)`/`tcdrain(3)`
 
   * Turn build error into compile warnings for exotic `struct stat`
     configurations (GHC #8859).
diff --git a/configure.ac b/configure.ac
index 24ea3a5..f883624 100644
--- a/configure.ac
+++ b/configure.ac
@@ -80,6 +80,19 @@ AC_CHECK_DECLS([fdatasync],[AC_CHECK_FUNCS([fdatasync])])
 
 AC_CHECK_FUNCS([posix_fadvise posix_fallocate])
 
+# Some termios(3) functions known to be missing sometimes (see also #55)
+AC_CHECK_DECLS([tcdrain],[AC_DEFINE([HAVE_TCDRAIN],[1],[Define to 1 if you have the `tcdrain' function.])],[],[AC_INCLUDES_DEFAULT
+#ifdef HAVE_TERMIOS_H
+#include <termios.h>
+#endif
+])
+
+AC_CHECK_DECLS([ctermid],[AC_DEFINE([HAVE_CTERMID],[1],[Define to 1 if you have the `ctermid' function.])],[],[AC_INCLUDES_DEFAULT
+#ifdef HAVE_TERMIOS_H
+#include <termios.h>
+#endif
+])
+
 # Avoid adding rt if absent or unneeded
 # shm_open needs -lrt on linux
 AC_SEARCH_LIBS(shm_open, rt, [AC_CHECK_FUNCS([shm_open shm_unlink])])