[PATCH bpf-next] libbpf: Add explicit padding to btf_dump_emit_type_decl_opts

[PATCH bpf-next] libbpf: Add explicit padding to btf_dump_emit_type_decl_opts

[KP Singh]

Similar to
https://lore.kernel.org/bpf/20210313210920.1959628-2-andrii@kernel.org/

When DECLARE_LIBBPF_OPTS is used with inline field initialization, e.g:

  DCLARE_LIBBPF_OPTS(btf_dump_emit_type_decl_opts, opts,
    .field_name = var_ident,
    .indent_level = 2,
    .strip_mods = strip_mods,
  );

and compiled in debug mode, the compiler generates code which
leaves the padding uninitialized and triggers errors within libbpf APIs
which require strict zero initialization of OPTS structs.

Adding anonymous padding field fixes the issue.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Fixes: 9f81654eebe8 ("libbpf: Expose BTF-to-C type declaration emitting API")
Signed-off-by: KP Singh <kpsingh@kernel.org>
---
 tools/lib/bpf/btf.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 3b0b17ba94a1..b54f1c3ebd57 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -176,6 +176,7 @@ struct btf_dump_emit_type_decl_opts {
 	int indent_level;
 	/* strip all the const/volatile/restrict mods */
 	bool strip_mods;
+	size_t :0;
 };
 #define btf_dump_emit_type_decl_opts__last_field strip_mods
 
-- 
2.31.0.rc2.261.g7f71774620-goog