logarithm in OpenSSL

[Guido Vranken]

If you want to use the log() from math.h, then you must compile with -lm,
eg.: clang source.c -lm

The log() in math.h only supports floating point numbers. If you require
computing logarithms of bignums, try https://www.mpfr.org/

On Wed, Jul 24, 2019 at 6:39 PM Niklas Niere <nniklas at mail.uni-paderborn.de>
wrote:

> Hello,
>
> we are implementing a TLS 1.3 feature into OpenSSL to get an idea of how
> well our feature performs in a concrete server library. In the feature,
> we want to use the log function.
>
> When we try to use the log function from the math.h header, OpenSSL
> won't compile with the statement that 'log' is a reference to an
> undefined function. The BigNum library from OpenSSL does also not seem
> to offer a log function.
>
> We suspect that the compile error comes from the fact that OpenSSL is
> C90 compatible but are unsure. Does anyone know how to compute the
> logarithm of a number in OpenSSL?
>
> Thanks,
> Niklas
>
>
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