Hello again, the problem was solved.

The compiler and SDKs were OK, however, the problem came from the environment variables. The ones pre-defined neither weren't the right ones, so I tried to execute Fluent from the MS VS2017 command prompt, succeeding at building and loading the udf. Once there, I typed 'env' on the command prompt and got all of the environment variables.

It appears there were some of them that weren't actually defined, so I had to creat them and then I became able to work with udf archives from ANSYS Fluent. I understand the proper installation of ANSYS should have defined them, but it didn't (there are some .exe called 'setenv' in order to do so).