[PATCH bpf-next] libbpf: handle invalid typedef emitted by old GCC

Andrii Nakryiko
2019-10-11T03:29:25Z

Old GCC versions are producing invalid typedef for __gnuc_va_list
pointing to void. Special-case this and emit valid:

typedef __builtin_va_list __gnuc_va_list;

Reported-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
tools/lib/bpf/btf_dump.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 87f27e2664c5..139812b46c7b 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -975,6 +975,17 @@ static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
{
const char *name = btf_dump_ident_name(d, id);

+ /*
+ * Old GCC versions are emitting invalid typedef for __gnuc_va_list
+ * pointing to VOID. This generates warnings from btf_dump() and
+ * results in uncompilable header file, so we are fixing it up here
+ * with valid typedef into __builtin_va_list.
+ */
+ if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
+ btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
+ return;
+ }
+
btf_dump_printf(d, "typedef ");
btf_dump_emit_type_decl(d, t->type, name, lvl);
}
--
2.17.1