On 2020-06-02, Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:
> the enum definition of BPF_F_CTXLEN_MASK is certainly within standard.
> I don't think kernel should adjust its headers because some compiler
> is failing to understand C standard.
This is not true. See C11 6.7.2.2p2: "The expression that defines the
value of an enumeration constant shall be an integer constant
expression that has a value representable as an int."
You can also see this with gcc if you turn on -Wpedantic and include
it in a way such that warnings are not silenced:
$ gcc -Wpedantic -x c -c -o /dev/null /usr/include/linux/bpf.h
/usr/include/linux/bpf.h:76:7: warning: ISO C forbids zero-size array
'data' [-Wpedantic]
76 | __u8 data[0]; /* Arbitrary size */
| ^~~~
/usr/include/linux/bpf.h:3220:22: warning: ISO C restricts enumerator
values to range of 'int' [-Wpedantic]
3220 | BPF_F_INDEX_MASK = 0xffffffffULL,
| ^~~~~~~~~~~~~
/usr/include/linux/bpf.h:3221:23: warning: ISO C restricts enumerator
values to range of 'int' [-Wpedantic]
3221 | BPF_F_CURRENT_CPU = BPF_F_INDEX_MASK,
| ^~~~~~~~~~~~~~~~
/usr/include/linux/bpf.h:3223:23: warning: ISO C restricts enumerator
values to range of 'int' [-Wpedantic]
3223 | BPF_F_CTXLEN_MASK = (0xfffffULL << 32),
| ^
/usr/include/linux/bpf.h:3797:8: warning: ISO C forbids zero-size
array 'args' [-Wpedantic]
3797 | __u64 args[0];
| ^~~~
$
-Michael
