[scott_s]

Calling G-Free an independent layer between the compiler and the assembler is a semantic distinction, not an implementation distinction. The step needs to live in either the compiler (as a post-processing phase) or the assembler (as a pre-processing phase) to be automatically integrated into the software stack.

[onars]

Using your terms, it is an implementation distinction as well. You install G-Free, call 'make' to build any software, it comes out gadget free. You delete G-free, call make, it comes out with gadgets. With our prototype implementation for Linux and GCC, you don't need to touch gcc or gas or the linker or anything else. This is explained in the paper.

If you have a build system where the assembler and the compiler are bundled as a monolithic binary executable, then your argument may or may not hold.

EDIT: Just to clarify, 'make' was just an example. You can also directly call "gcc program.c" or "as anotherprogram.S" and G-Free does its job.