Getting byte size of a c++ struct given as a string

Question

I have the following problem. I am given a string. This string represents is a valid c++ struct.

I need to figure out the fastest way to get the size in bytes of this struct.

The most obvious approach to me is:

Write struct to a file and turn that file into a script that writes the size to a file, call a compiler from the system, compile the file, run the executable, parse the file.

This is absurd, there has to be a better way.

I have heard about GCC's JITC library, that might be a better approach. But since I don;t need full blown compilation there might be a simpler way?

The struct is represented as it would in native c++ code, i.e. I have this string

"struct MySstruct { int field1; void* field2; short field3; };"

Would be the content of the string.