From: Andrii Nakryiko <andriin@fb.com>
Date: Thu, 10 Oct 2019 20:29:01 -0700
Subject: libbpf: Handle invalid typedef emitted by old GCC
Patch-mainline: v5.5-rc1
Git-commit: e78dcbf414545b53218dab0fb5af5d6b61513eaf
References: bsc#1177028

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>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20191011032901.452042-1-andriin@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
 tools/lib/bpf/btf_dump.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

--- 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(st
 {
 	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);
 }