c2rust panic when encounter `__counted_by__` attribute

[bungcip]

reduced testcase

struct {
  int length;
  unsigned char data[] __attribute__ ((__counted_by__ (length)));
} eed_4;

https://c.godbolt.org/z/1cMd7PveW

__counted_by__ introduced in clang 18.

[bungcip]

need to handle CountAttributedType in c2rust-ast-exporter to fix this.

[bungcip]

hmm, i think the problem only happens when compiling with clang >= 19. so in my system (clang 21) and goldbolt (clang 19) the program causing panic but in clang 18 is fine

[kkysen]

hmm, i think the problem only happens when compiling with clang >= 19. so in my system (clang 21) and goldbolt (clang 19) the program causing panic but in clang 18 is fine

I'm not sure if you're aware (nevermind if you already are), but you can set LLVM_CONFIG_PATH to set the llvm/clang version you compile against. That should help debugging locally if you install the other clang versions.