[ ghc-Bugs-448104 ] imported return type not masked

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Bugs item #448104, was opened at 2001-08-05 00:44
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Category: Compiler (FFI)
Group: 5.00
Status: Open
Resolution: None
Priority: 5
Submitted By: Ashley Yakeley (ashley-y)
>Assigned to: Julian Seward (sewardj)
Summary: imported return type not masked

Initial Comment:
This might be difficult to reproduce. Try this:

Haskell looks like this:

foreign import foo :: IO Word8

do {
 f <- foo;
 putStrLn (show f);
}

C looks like this:

HsWord8 foo ()
  {
  HsWord8 f;
  ... f should be zero
  return f;
  }

On running, I might get something like this:
1074803456

...which is clearly not a Word8, although the low byte is zero.

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>Comment By: Ashley Yakeley (ashley-y)
Date: 2001-10-07 21:51

Message:
Logged In: YES 
user_id=19233

I take it this is not fixed in 5.02...

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Comment By: Ashley Yakeley (ashley-y)
Date: 2001-08-05 17:25

Message:
Logged In: YES 
user_id=19233

My setup:

$ ghc -v
Glasgow Haskell Compiler, Version 5.00, for Haskell 98, compiled by GHC 
version 5.00
Using package config file: /usr/lib/ghc-5.00/package.conf
Hsc static flags: -static -fignore-interface-pragmas -fomit-interface-pragmas 
-fdo-lambda-eta-expansion -flet-no-escape

$ uname -a
Linux server 2.2.19pre17 #1 Tue Mar 13 22:37:59 EST 2001 i686 unknown


----------------------------------------------------------------------

Comment By: Ashley Yakeley (ashley-y)
Date: 2001-08-05 17:18

Message:
Logged In: YES 
user_id=19233

OK, here's an example:

extern "C"
	{
	unsigned char foo();
	}

inline void use(const char* s)
	{
	}

unsigned char foo()
	{
	const char* s = "";
	use(s);
	return 0;
	}

...and the Haskell looks something like this:

 foreign import foo :: IO Word8

do {
 w8 <- foo;
 putStrLn (show (w8 :: Word8));
}

...and the result is this:
1074803712

Note that the low byte of this value is (correctly) zero. Unfortunately the high three 
bytes are not.

----------------------------------------------------------------------

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