Question

I’m porting an existing Windows application to Linux.

The most of the OS APIs\ Microsoft non-standard extension functions can be easily (more or less…) replaced by equivalent Linux\ GCC APIs, however, I don’t know how to deal with sprintf_s which gets variable numbers of arguments.

Does anyone have an idea (If you can please put the code example as well) for that?

Thank you all in advance.

Answer 1

First, can you just port your code to use C++ iostreams instead (for example ostringstream)? This would completely remove all the possible issues with the sprintf line of functions, and if there are a limited number of call points is probably the best option.

If that isn’t an option: The sprintf_s function is basically a helper to prevent mistakes (and external abuse to cause buffer overflows. From http://msdn.microsoft.com/en-us/library/ce3zzk1k%28VS.80%29.aspx we learn that it does two things: It checks the format string for valid formats (this doesn’t mean it does type checking – it still can’t do that), and it allows a max length to be specified.

The best replacement will be snprintf which does have limitations compared to sprintf_s. It won’t do format string validation. And not all versions guarantee that the final string will be null terminated: You always want to also store a null into the last character of your buffer after the call to ensure that the final string is null terminated.