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Sprintf not supported with c codegen. Which is the workaround?

Asked by Oriol Rios on 4 Aug 2016
Latest activity Commented on by Walter Roberson
on 20 Jun 2017
SPRINTF is not a codegen supported function (although fprintf is). I tried to create a dedicated MEX but does not work. Does any one can figure out a workaround? Could not find any working example with coder.ceval neither
Thanks!

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3 Answers

Answer by Tom Clark on 20 Sep 2016
 Accepted Answer

The accepted answer on this SO post shows one way of doing it (for ints) which could be adapted to floats, presumably).
I think it's a really massive shortcoming that coder can't do such a basic thing!

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Thanks Tom!
I kind of found a workaround by manually scripting a C functions with its gateway that does the job (particular to my problem). Your answer might be a solution too.
Many thanks!

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Answer by Nathan Zimmerman on 20 Jun 2017

How on earth has matlab been around for so long with all these code generation tools but converting a number to a string is not supported? Dear lord why? How many thousands of dollars do these code tools cost again?

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num2str() or sprintf() to string has a variable length result. That is a problem when generating for embedded hardware with limited memory, as embedded hardware for real-time work usually requires fixed length buffers. The C language function sprintf() does not accept a buffer size, so it tends to lead to buffer overflow problems, including deliberate security attacks. (Remember, although you can give precision modifiers to sprintf, they are always minima and sprintf will use more characters if it needs to.)
You really need C snprintf() or vsnprintf() calls, but those came out in C99 and were not present in C89.
One thing to keep in mind in this respect is that Microsoft has said clearly that Visual Studio will not be made C99 compliant, because Visual Studio is intended to be primarily a C++ compiler, so Microsoft only implemented the parts of C99 that were directly compatible with C++99 (or later updates, depending on the VS edition you get.)
It appears to me that snprintf() does exist in C++ so it is probably supported by VS in C mode -- the point here is that limitations like these can be a lot more subtle than is at first apparent.

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Answer by Azzi Abdelmalek
on 4 Aug 2016

You can use num2str

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No, num2str is not supported for code generation either.

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