Question

How do I determine what my compiler (g++) is doing with template code?

I am using boost.proto (an expression-template library) to evaluate some maths expressions at compile time. The code evaluates the expressions correctly, but I would like to see whether the compiler has expanded out the expression to the equivalent of hand-written c-code (i.e. eliminated all the temporaries), or whether there is still some further compile-time optimizations to be done.

Is there a way to see what the compiler has done with the templates?

Thanks

Answer 1

There are several ways to see a C++ code after the templates instantiation pass:

• Use gcc -fdump-tree-original (or even -fdump-tree-all to see more passes)
• Use Elsa C++ parser: http://scottmcpeak.com/elkhound/sources/elsa/
• Use Clang and an LLVM C backend – the latter will give the most unreadable code, but it is still useful in some cases. There should be some AST dumping functionality in Clang itself as well.