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From: matts@microsoft.UUCP (Matt SAETTLER)
Newsgroups: comp.windows.ms
Subject: Re: Possible bug in tricky use of wsprintf - MSC 6.0
Message-ID: <57612@microsoft.UUCP>
Date: 21 Sep 90 04:03:40 GMT
References: <6578@sugar.hackercorp.com> <57528@microsoft.UUCP> <960@metapyr.UUCP>
Reply-To: matts@microsoft.UUCP (Matt Saettler)
Organization: Microsoft Corp., Redmond WA
Lines: 45

In article <960@metapyr.UUCP> marc@metapyr.UUCP (Marc Paige - The Karate Kid ) writes:
]In article <57528@microsoft.UUCP> kensy@microsoft.UUCP (Ken SYKES) writes:
]>In article <6578@sugar.hackercorp.com> karl@hackercorp.com (Karl Lehenbauer) writes:
]>>Looks like wsprintfs of the form:
]>>
]>>	wsprintf(outstr, "%.*s", numchars, text);
]>>
]>>...cause a trap.  I'll be sure in a bit.  In the meantime, beware.
]>>-- 
]>
]>The * operator is not supported by wsprintf (look at the width description
]>in the SDK.)  As a result it thinks numchars is the first part of the 
]>string address then starts grabbing values from the bogus address.  Thus
]>the fault.  You could get around this by writing a replacement that 
]>handles the '*' by using wsprintf to convert the control string to a static
]>string (replace *'s with the contents of numchar) then call wvsprintf to
]>do the actual command.  Sloppy yes, but wsprintf is not documented as a 
]>replacement for sprintf.  Consequently some of the features may not be
]>provided.
]>Ken Sykes
]
]WHOA!  The asterisk's got nothing to do with it!  If Karl is using the medium
]model (as he should be :-( I hate the medium model) then the constant being
]passed by "%.*s" is a NEAR pointer.  NEAR pointers passed to FAR pointer
]functions cause a trap 13.  I ported a 2.11 program that had to use sprintf
]for the error message system.  Converting all the sprintf's to wsprintf's
]made me painfully aware of this fact.  Cast the "%.*s" to (LPSTR) and the
]trap should be gone.  As a matter of fact, I just had to fix one of these
]little casts that I missed the first time.  Caused "Unrecoverable Application
]Error".  NOTE: All string arguments in the wsprintf call are LPSTR
]               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
]and must be either cast that way or generated by GlobalAlloc.  This should
]help.
]

The * IS the problem.  The string constant will be automatically cast
by the compiler because the prototyp for wsprintf specifies an LPSTR.

From windows.h:
int FAR cdecl wsprintf(LPSTR,LPSTR,...);

However,  Text will have to be explicitly cast if it is not an LPSTR.

------------------
These are my own thoughts, or so I'm told to say.