_stprintf
in [MFC]
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From: Vipin on 30 Jul 2006 01:55 using StringCchPrintf would need linking to strsafe.lib. The issue of buffer overflow can be handled with snprintf and alike. -- Vipin Aravind http://www.explorewindows.com "Joseph M. Newcomer" <newcomer(a)flounder.com> wrote in message news:e57oc2lrr2nd1j0nt83h8e7h02ahjsbqih(a)4ax.com... > It cannot be causing a "storage leak" since there is no allocation > involved. > > You should generally avoid _stprintf whenever possible. Use > CString::Format as the > preferred choice. If you MUST use some form like _stprintf, use > StringCchPrintf (I think > that's the name, but search for strsafe.h on the MSDN) which at least will > avoid any > possibility of buffer overflow > > It would help a lot if you did something like > > StringCchPrintf(_T("%c"), B, sizeof(B) / sizeof(TCHAR), (BYTE)('a' + i)); > > This eliminates several problems: > 1. No buffer overflow if you make an error > 2. The value is not treated as a signed value and therefore sign extended > (see problem 1) > > However, your actual problem is even simpler; it would have been better to > do > TCHAR B[2]; > B[0] = _T('a') + i; > B[1] = _T('\'0'); > > which eliminates the need to call a subroutine to do a fundamentally > trivial computation. > > I assume you meant %c because %a is not documented. > joe > > On Sat, 29 Jul 2006 13:17:02 -0700, Sonu <sonu(a)online.nospam> wrote: > >>Hello all, >>I am having trouble with _stprintf(). It's a Unicode application. >> >>TCHAR B[5]; >>_stprintf( B, _T("%a"), 'a' + i); >> >>so if the value if i=9, I want B to be "j". But instead the value in B is >>"-0x1.c39360p+117" >> >>And this is causing all kinds of memory leaks and strange behaviours... >> >>Any help appreciated >>Thanks >>Srishti > Joseph M. Newcomer [MVP] > email: newcomer(a)flounder.com > Web: http://www.flounder.com > MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Mihai N. on 30 Jul 2006 04:35 > StringCchPrintf(_T("%c"), B, sizeof(B) / sizeof(TCHAR), (BYTE)('a' + i)); Casting to BYTE first is a problem. If i is a high-value Unicode thing, the result is truncated. But I have to also wonder why someone would add something to a character. The only reasonable use for that would be some kind of encryption. But that has to be thought out for Unicode, when migrating. And, in general, home-brewed encryption algorithms are bad idea. -- Mihai Nita [Microsoft MVP, Windows - SDK] http://www.mihai-nita.net ------------------------------------------ Replace _year_ with _ to get the real email
From: Mihai N. on 30 Jul 2006 04:35 > StringCchPrintf(_T("%c"), B, sizeof(B) / sizeof(TCHAR), (BYTE)('a' + i)); Casting to BYTE first is a problem. If i is a high-value Unicode thing, the result is truncated. But I have to also wonder why someone would add something to a character. The only reasonable use for that would be some kind of encryption. But that has to be thought out for Unicode, when migrating. And, in general, home-brewed encryption algorithms are bad idea. -- Mihai Nita [Microsoft MVP, Windows - SDK] http://www.mihai-nita.net ------------------------------------------ Replace _year_ with _ to get the real email
From: Joseph M. Newcomer on 30 Jul 2006 17:22 Good point. I was not being careful enough; that should have been WORD (there is no UTCHAR as far as I know). It can't be a signed value such as TCHAR because then it will sign-extend when it converts it to an integer. Homebrewed encryption is *always* a bad idea, but I suspect this is more likely trying to do some kind of character conversion. (There are very few people who can successfully do data encryption; one of the few I personally know has a PhD and his dissertation was on encryption algorithms) joe On Sun, 30 Jul 2006 01:35:30 -0700, "Mihai N." <nmihai_year_2000(a)yahoo.com> wrote: >> StringCchPrintf(_T("%c"), B, sizeof(B) / sizeof(TCHAR), (BYTE)('a' + i)); >Casting to BYTE first is a problem. >If i is a high-value Unicode thing, the result is truncated. > >But I have to also wonder why someone would add something to a character. >The only reasonable use for that would be some kind of encryption. >But that has to be thought out for Unicode, when migrating. >And, in general, home-brewed encryption algorithms are bad idea. Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Mihai N. on 31 Jul 2006 04:50
> Homebrewed encryption is *always* a bad idea, I was trying to be mild :-) > but I suspect this is more likely trying to > do some kind of character conversion. This is probably also bad idea :-) Doing any kind of "math" on Unicode characters is very likely to result in a mess. -- Mihai Nita [Microsoft MVP, Windows - SDK] http://www.mihai-nita.net ------------------------------------------ Replace _year_ with _ to get the real email |