[freetds] CS_INT size bug

entropy at freetds.org entropy at freetds.org
Wed Sep 6 00:59:00 EDT 2006


Lowden, James K wrote:

> The question I have is: Should we change our definition of CS_INT in
> FreeTDS?   In my copy of csconfig.h from Sybase 12.0 (for Win32) I have:
> 
> /*
> ** Certain Sybase C datatypes must be defined as 4 bytes in size. The
> ** following insures that all platforms (including 64 bit machines) use
> ** the correct C native types.
> */
> #if defined( __alpha) || defined(SYB_LP64) || defined(_AIX)
> typedef int             CS_INT;
> typedef int             CS_RETCODE;
> typedef int             CS_BOOL;
> typedef unsigned int    CS_UINT;
> #else
> typedef long            CS_INT;
> typedef long            CS_RETCODE;
> typedef long            CS_BOOL;
> typedef unsigned long   CS_UINT;
> #endif
> 
> FreeTDS doesn't define or honor SYB_LP64, yet we define CS_INT as
> tds_sysdep_int32_type i.e. 'int' on most (all?) 32-bit architectures.
> That disagrees with Sybase's file.  If we want application code to
> compile cleanly irrespective of which library (Sybase's or FreeTDS) is
> used, then we need to change our header file.  
> 
> I don't know the history of SYB_LP64, so I don't know whether we should
> support it.  And I don't know if it's important to be compatible in this
> way with Sybase's choices.  But my instinct, a priori, is that we should
> be compatible without replicating bugs.  

I think we already are compatible in the way that matters:  our CS_INT 
is 4 bytes long.  The whole point of that conditional code in the Sybase 
header is to ensure that CS_INT is a 32-bit integer type (read the 
comment!)  Whether that type happens to be called "int" or "long" really 
isn't terribly important.

> OTOH, the Client Library Programmer's Guide says: 
> 
> 	"Open Client/Server datatypes also permit application source
> code to be 
> ported between platforms. For example, a CS_INT is always mapped to a
> system
> datatype that matches a four-byte integer."
> 
> "[M]apped to ... a four-byte integer."  Strictly speaking, that's
> exactly what we do with:
> 
> $ grep  CS_INT include/* | grep typedef
> include/cstypes.h:typedef tds_sysdep_int32_type CS_INT;
> 
> Nevertheless, there are undoubtedly many applications that assume CS_INT
> is long, simply because Sybase says it is unless "defined( __alpha) ||
> defined(SYB_LP64) || defined(_AIX)".  And we could make the user's life
> easier by following Sybase's lead.  Or we could adhere to the letter of
> the law and suggest users with such code either make it portable or
> exercise their license to change the header file.

Any user code that assumes CS_INT is long is broken, because we know 
there are cases where CS_INT *is not* long.  Application code, to be 
strictly correct in both LP32 and LP64 environments must be able to cope 
with those cases.  I've already provided code that shows how easy that 
is to do, so I think it's pointless to change.

I have no strong objection to trying to use "long" in preference to 
"int" when both are 32-bit types, but I do think it's a waste of time. 
We're long past the days when "all the world's a VAX", and it's time for 
application coders to start learning how to use the C language properly. 
  A few extra warnings to nudge them in the right direction isn't a bad 
thing.

IMNSHO, of course.

-- 
Cheers,
entropy



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