On Sep 28, 2019, at 10:49 PM, Gustavo A. R. Silva [off-list ref] wrote:



On 9/28/19 09:48, Stephen Kitt wrote:

quoted

This switches zero-length arrays in variable-length structs to C99
flexible array members. GCC will then ensure that the arrays are
always the last element in the struct.

Coccinelle:
@@
identifier S, fld;
type T;
@@

struct S {
 ...
- T fld[0];
+ T fld[];
 ...
};

Signed-off-by: Stephen Kitt <redacted>
---
Documentation/bpf/btf.rst       | 2 +-
tools/lib/bpf/libbpf.c          | 2 +-
tools/lib/bpf/libbpf_internal.h | 2 +-
3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Documentation/bpf/btf.rst b/Documentation/bpf/btf.rst
index 4d565d202ce3..24ce50fc1fc1 100644
--- a/Documentation/bpf/btf.rst
+++ b/Documentation/bpf/btf.rst

@@ -670,7 +670,7 @@ func_info for each specific ELF section.::
        __u32   sec_name_off; /* offset to section name */
        __u32   num_info;
        /* Followed by num_info * record_size number of bytes */
-        __u8    data[0];
+        __u8    data[];
     };

Here, num_info must be greater than 0.

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index e0276520171b..c02ea0e1a588 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -5577,7 +5577,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt,

struct perf_sample_raw {
	struct perf_event_header header;
	uint32_t size;
-	char data[0];
+	char data[];
};

struct perf_sample_lost {

diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
index 2e83a34f8c79..26eaa3f594aa 100644
--- a/tools/lib/bpf/libbpf_internal.h
+++ b/tools/lib/bpf/libbpf_internal.h

@@ -86,7 +86,7 @@ struct btf_ext_info_sec {

	__u32	sec_name_off;
	__u32	num_info;
	/* Followed by num_info * record_size number of bytes */
-	__u8	data[0];
+	__u8 data[];

I think you should preserve the tab here.

Agreed. 

Besides this:

Acked-by: Song Liu <redacted>