Avoid calling varargs functions using the FFI

Calling varargs functions is explicitly deprecated according to the
FFI specification.  It used to work, just about, but it broke with the
recent changes to the via-C backend to not use header files.

4 files changed, 18 insertions, 2 deletions

diff --git a/libraries/base/Control/Exception.hs b/libraries/base/Control/Exception.hs
index 3fc1139ff8..14bdef138c 100644
--- a/libraries/base/Control/Exception.hs
+++ b/libraries/base/Control/Exception.hs
@@ -581,7 +581,9 @@ uncaughtExceptionHandler = unsafePerformIO (newIORef defaultHandler)
           withCString msg $ \cmsg ->
             errorBelch cfmt cmsg
 
-foreign import ccall unsafe "RtsMessages.h errorBelch"
+-- don't use errorBelch() directly, because we cannot call varargs functions
+-- using the FFI.
+foreign import ccall unsafe "HsBase.h errorBelch2"
    errorBelch :: CString -> CString -> IO ()
 
 setUncaughtExceptionHandler :: (Exception -> IO ()) -> IO ()
diff --git a/libraries/base/Debug/Trace.hs b/libraries/base/Debug/Trace.hs
index c30c8111d1..742044e4d4 100644
--- a/libraries/base/Debug/Trace.hs
+++ b/libraries/base/Debug/Trace.hs
@@ -41,7 +41,9 @@ putTraceMsg msg = do
      withCString msg  $ \cmsg ->
       debugBelch cfmt cmsg
 
-foreign import ccall unsafe "RtsMessages.h debugBelch"
+-- don't use debugBelch() directly, because we cannot call varargs functions
+-- using the FFI.
+foreign import ccall unsafe "HsBase.h debugBelch2"
    debugBelch :: CString -> CString -> IO ()
 #endif
 
diff --git a/libraries/base/cbits/PrelIOUtils.c b/libraries/base/cbits/PrelIOUtils.c
index f37c4b6726..556736e86b 100644
--- a/libraries/base/cbits/PrelIOUtils.c
+++ b/libraries/base/cbits/PrelIOUtils.c
@@ -7,3 +7,12 @@
 #define INLINE
 #include "HsBase.h"
 
+void errorBelch2(const char*s, char *t)
+{
+    return errorBelch(s,t);
+}
+
+void debugBelch2(const char*s, char *t)
+{
+    return debugBelch(s,t);
+}
diff --git a/libraries/base/include/HsBase.h b/libraries/base/include/HsBase.h
index 8e5676abe4..f69e9cf656 100644
--- a/libraries/base/include/HsBase.h
+++ b/libraries/base/include/HsBase.h
@@ -732,5 +732,8 @@ INLINE void *    __hscore_from_intptr (intptr_t n)  { return (void *)n; }
 INLINE uintptr_t __hscore_to_uintptr  (void *p)     { return (uintptr_t)p; }
 INLINE intptr_t  __hscore_to_intptr   (void *p)     { return (intptr_t)p; }
 
+void errorBelch2(const char*s, char *t);
+void debugBelch2(const char*s, char *t);
+
 #endif /* __HSBASE_H__ */