I am using systemC with visual C++ 2008. I wrote a simple hello world program. However I am getting this error repeatedly:
warning C4996: 'sprintf': This function or variable may be unsafe.
Why this is happening? I would appreciate any help.
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It's a warning, not an error.Philippe– Philippe2012-01-31 09:52:46 +00:00Commented Jan 31, 2012 at 9:52
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2 Answers
The compiler warns against sprintf() use because it may cause buffer overflow since it doesn't check buffer's limit. Instead, use snprintf() which never fills the buffer beyond the passed-in limit.
This advice is also given by the manpage:
Because sprintf() and vsprintf() assume an arbitrarily long string, callers must be careful not to overflow the actual space; this is often impossible to assure. Note that the length of the strings produced is locale-dependent and difficult to predict. Use snprintf() and vsnprintf() instead (or asprintf(3) and vasprintf(3)).
2 Comments
paxdiablo
"this is often impossible to assure" only if you're an idiot. People who have been coding in C for long enough know the difference between truly insecure stuff (like
gets, or scanf("%s") where you don't control the input) and stuff like sprintf where you can make it safe. Everyone else should go back to using VB :-) I always turn off these warnings with a #define since I know what I'm doing.
Adam Zalcman
I do agree that
gets() and sprintf() fall into different categories when it comes to potential for vulnerabilities, but there is a danger in using sprintf() which you have not mentioned and which is connected with maintenance: it's easy to forget to update buffer size when you modify the format string or other parameters passed to sprintf().It's insecure because - From MSDN
There is no way to limit the number of characters written, which means that code using sprintf is susceptible to buffer overruns. Consider using the related function _snprintf, which specifies a maximum number of characters to be written to buffer, or use _scprintf to determine how large a buffer is required. Also, ensure that format is not a user-defined string.
3 Comments
ta.speot.is
It's not insecure, it may be insecure.
paxdiablo
Yes, it's only insecure if you don't know what you're doing.
johnsyweb
@skeptic: "thanks everyone" is best expressed "by clicking on the check box outline to the left of the answer."
