Use some validation suite for C to check for standard conformance or bugs

[feroldi]

There are two approaches to end-to-end validations that we wish to have: execution behavior, and assembly output. The first one compiles a set of C source codes, and runs the executable to check against an expected output (i.e., stdout, and stderr). The second one also compiles a set of C source codes, but instead of executing the program, it compares the assembly output against an expected one.

We could work on a validation suite ourselves for the first approach, but that sounds like a lot of work, and I'm no standard specialist either. We are inevitably going to work on the second approach ourselves, as that's a result of test driven development.

There are a few options out there that we could check out:

• Plum Hall: http://www.plumhall.com/stec.html
• c-testsuite: https://github.com/c-testsuite/c-testsuite
• GCC C Tests: https://gcc.gnu.org/onlinedocs/gccint/C-Tests.html#C-Tests