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| author | Alan Maguire <alan.maguire@oracle.com> | 2024-06-24 20:29:03 +0100 |
|---|---|---|
| committer | Andrii Nakryiko <andrii@kernel.org> | 2024-06-26 16:38:59 -0700 |
| commit | 0f31c2c61f6923747628c65a0fe36b2d4d7e21b0 (patch) | |
| tree | 12f2bebc7c7747f1b0c4a3f4e956c808bf1a22bd /tools/lib/bpf | |
| parent | d07980f7373b4c57c85478f8e815cc7b9b394c05 (diff) | |
| download | lwn-0f31c2c61f6923747628c65a0fe36b2d4d7e21b0.tar.gz lwn-0f31c2c61f6923747628c65a0fe36b2d4d7e21b0.zip | |
libbpf: Fix clang compilation error in btf_relocate.c
When building with clang for ARCH=i386, the following errors are
observed:
CC kernel/bpf/btf_relocate.o
./tools/lib/bpf/btf_relocate.c:206:23: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
206 | info[id].needs_size = true;
| ^ ~
./tools/lib/bpf/btf_relocate.c:256:25: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion]
256 | base_info.needs_size = true;
| ^ ~
2 errors generated.
The problem is we use 1-bit, 31-bit bitfields in a signed int.
Changing to
bool needs_size: 1;
unsigned int size:31;
...resolves the error and pahole reports that 4 bytes are used
for the underlying representation:
$ pahole btf_name_info tools/lib/bpf/btf_relocate.o
struct btf_name_info {
const char * name; /* 0 8 */
unsigned int needs_size:1; /* 8: 0 4 */
unsigned int size:31; /* 8: 1 4 */
__u32 id; /* 12 4 */
/* size: 16, cachelines: 1, members: 4 */
/* last cacheline: 16 bytes */
};
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240624192903.854261-1-alan.maguire@oracle.com
Diffstat (limited to 'tools/lib/bpf')
| -rw-r--r-- | tools/lib/bpf/btf_relocate.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/tools/lib/bpf/btf_relocate.c b/tools/lib/bpf/btf_relocate.c index 2281dbbafa11..17f8b32f94a0 100644 --- a/tools/lib/bpf/btf_relocate.c +++ b/tools/lib/bpf/btf_relocate.c @@ -58,8 +58,8 @@ struct btf_relocate { struct btf_name_info { const char *name; /* set when search requires a size match */ - int needs_size:1, - size:31; + bool needs_size: 1; + unsigned int size: 31; __u32 id; }; |