I can see posts as far back as 2010 that indicate Clang had support for FORTIFY_SOURCE, but I haven’t been able to find a commit to cite as the date when Clang got FORTIFY_SOURCE support. Could someone point me in the right direction on that?
(And as a lesser goal, perhaps when llvm-gcc obtained support for it?)
FORTIFY_SOURCE is the name of the library feature, not the compiler feature. The relevant compiler feature is __builtin_object_size; you should find lots of references to that in LLVM commit logs.