“Source-to-source” is redundant. You can just shorten this to “compiler”.

pawelmurias · on Aug 28, 2018

It's not redundant. A "source-to-source" compiler isn't a "source-to-machine code" compiler

sigjuice · on Aug 28, 2018

It is redundant. See page 1 of most compiler books.

Compilers: Principles, Techniques, and Tools

Simply stated, a compiler is a program that can read a program in one language - the source language - and translate it into an equivalent program in another language - the target language

Engineering a Compiler

Compilers are computer programs that translate a program written in one language into a program written in another language