creating a UDF for Mysql - Error 1127 cn't find symbol in library

[Mario Rossi]

I wrote a function in C ++ with Microsoft Visual Studio 2010
I believe I have followed all the rules for making udf for mysql
the program compiles perfectly without any error
then the dll is generated
then I copy it to the mysql lib folder
only that when I go to record it gives me the syntax error

https://www.dropbox.com/s/lrpi8xr5dztoppt/err1.png?dl=0

if instead the register com eINTEGER rather than DOUBLE

gives me this error

https://www.dropbox.com/s/rulajh89bam3c8i/err2.png?dl=0

this is the source

https://www.dropbox.com/s/hhysguksc2xp2b7/ato_simil_string.cpp?dl=0

I hope you can help me.
Thank you all

PS.
I created a post identical to this in the Italian section. I hope there are no problems :)