| Message ID | 20210317031257.846314-2-andrii@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | Generate NULL in vmlinux.h | expand |
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c index 62953bbf68b4..ff6a76632873 100644 --- a/tools/bpf/bpftool/btf.c +++ b/tools/bpf/bpftool/btf.c @@ -405,6 +405,8 @@ static int dump_btf_c(const struct btf *btf, printf("#ifndef __VMLINUX_H__\n"); printf("#define __VMLINUX_H__\n"); printf("\n"); + printf("#define NULL ((void *)0)\n"); + printf("\n"); printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n"); printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n"); printf("#endif\n\n");
Given that vmlinux.h is not compatible with headers like stdint.h, NULL poses an annoying problem: it is defined as #define, so is not captured in BTF, so is not emitted into vmlinux.h. This leads to users either sticking to explicit 0, or defining their own NULL (as progs/skb_pkt_end.c does). It's pretty trivial for bpftool to generate NULL definition, though, so let's just do that. This might cause compilation warning for existing BPF applications: progs/skb_pkt_end.c:7:9: warning: 'NULL' macro redefined [-Wmacro-redefined] #define NULL 0 ^ /tmp/linux/tools/testing/selftests/bpf/tools/include/vmlinux.h:4:9: note: previous definition is here #define NULL ((void *)0) ^ It is trivial to fix, though, so long-term benefits outweight temporary inconveniences. Signed-off-by: Andrii Nakryiko <andrii@kernel.org> --- tools/bpf/bpftool/btf.c | 2 ++ 1 file changed, 2 insertions(+)