Rewrite Of C++ Demanglers

[brightprogrammer]

Remove old GPL code from libiberty and completely rewrite both GNU v2 and GNU v3 demanglers with LGPL license.

Work plan :

• Rewrite src/gnu_v2
• Rewrite src/cxx
• More rigorous testing

Test plan :

• Already added in Add More GNU v2/v3 Tests #68
• Write a fuzzer (in less than 100 lines) as implemented in GCC?
• Build old GCC version (maybe using Qemu) and then compile and get [mangled, original] name pairs for testing.

Attachments :

• gnuv2-mangler-grammar-nfkDi4L3lb.pdf

[brightprogrammer]

We do need to find a way to test the GNU v2 code more like we do for GNU v3. There are very few examples. Also due to lack of a precise grammar, things like special naming conventions are hard for me to cover. Any suggestions?

[brightprogrammer]

There are some function parameter types for which tests don't exist. I haven't added them for now, because I won't have any way to test my implementation.

[wargio]

overall this looks very very good. great job!

[brightprogrammer]

This PR is going to get a bit messy. I'm going to make a split of the very large (around 28k lines) test/test_cxx.c file into multiple smaller files of 1000 tests max. Later on before the merge I can merge all these files back to a big one, or we can leave it this way for future cases.

Also, the split is done without any category. I'll focus on passing all tests in a single file at a time. Slowly cover all files.

I used the following command for the split :

split -d -l 1000 test_cxx.c test_cxx.

[brightprogrammer]

My current focus is only on passing all tests cases and completing the demangler as soon as possible, and later on we can worry about other failing CI. Every CI is at the time of writing...