On Wed, Dec 18, 2019 at 11:06:56PM -0800, Andrii Nakryiko wrote:
> + if (core_mode) {
> + printf("#if defined(__has_attribute) && __has_attribute(preserve_access_index)\n");
> + printf("#define __CLANG_BPF_CORE_SUPPORTED\n");
> + printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
> + printf("#endif\n\n");
I think it's dangerous to automatically opt-out when clang is not new enough.
bpf prog will compile fine, but it will be missing co-re relocations.
How about doing something like:
printf("#ifdef NEEDS_CO_RE\n");
printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
printf("#endif\n\n");
and emit it always when 'format c'.
Then on the program side it will look:
#define NEEDS_CO_RE
#include "vmlinux.h"
If clang is too old there will be a compile time error which is a good thing.
Future features will have different NEEDS_ macros.
