logarithm in OpenSSL

[Niklas Niere <nniklas@xxxxxxxxxxxxxxxxxxxxx>]

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