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

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Message-ID: <20191011032901.452042-1-andriin@fb.com>
Date:   Thu, 10 Oct 2019 20:29:01 -0700
From:   Andrii Nakryiko <andriin@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>, <john.fastabend@...il.com>
CC:     <andrii.nakryiko@...il.com>, <kernel-team@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: [PATCH bpf-next] libbpf: handle invalid typedef emitted by old GCC

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@...il.com>
Signed-off-by: Andrii Nakryiko <andriin@...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