[PATCH v2] gas: fix building tc-bpf.c on s390x

[Jan Beulich]

On 03.05.2023 14:02, Ilya Leoshkevich wrote:
> char is unsigned on s390x, so there are a lot of warnings like:
> 
>     gas/config/tc-bpf.c: In function 'get_token':
>     gas/config/tc-bpf.c:900:14: error: comparison is always false due to limited range of data type [-Werror=type-limits]
>       900 |       if (ch == EOF || len > MAX_TOKEN_SZ)
>           |              ^~
> 
> Change its type to int, like in the other similar code.
> 
> There is also:
> 
>     gas/config/tc-bpf.c:735:30: error: 'bpf_endianness' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>       735 |    dst, be ? size[endianness - BPF_BE16] : size[endianness - BPF_LE16]);
>           |                   ~~~~~~~~~~~^~~~~~~~~~
> 
> -Wmaybe-uninitialized doesn't seem to understand the FSM; just
> initialize bpf_endianness to silence it.  Add an assertion to
> build_bpf_endianness() in order to catch potential bugs.
> ---
> 
> v1: https://sourceware.org/pipermail/binutils/2023-April/127235.html
> v1 -> v2: Change signed char to int (Jan).
>           Add an assertion.

Looks okay to me now, but will want Jose's approval.

I'm a little puzzled, btw, why e.g. bpf_atomic_insn doesn't also expose
a "maybe uninitialized" warning.

Jan

> --- a/gas/config/tc-bpf.c
> +++ b/gas/config/tc-bpf.c
> @@ -730,6 +730,8 @@ build_bpf_endianness (char *dst, enum bpf_token_type endianness)
>        || endianness == BPF_LE32
>        || endianness == BPF_LE64)
>      be = 0;
> +  else
> +    gas_assert (endianness == BPF_BE16 || endianness == BPF_BE32 || endianness == BPF_BE64);
>  
>    bpf_insn = xasprintf ("%s %%%s,%s", be ? "endbe" : "endle",
>  			dst, be ? size[endianness - BPF_BE16] : size[endianness - BPF_LE16]);
> @@ -885,7 +887,7 @@ get_token (const char **insn, char *token, size_t *tlen)
>      } while (0)
>  
>    const char *str = *insn;
> -  char ch, ch2 = 0;
> +  int ch, ch2 = 0;
>    enum bpf_token_type ttype = BPF_UNKNOWN;
>    size_t len = 0;
>    const char *expr = NULL;
> @@ -1362,7 +1364,7 @@ bpf_pseudoc_to_normal_syntax (const char *str, char **errmsg)
>      } while (0)
>  
>    enum bpf_token_type ttype;
> -  enum bpf_token_type bpf_endianness,
> +  enum bpf_token_type bpf_endianness = BPF_UNKNOWN,
>  		      bpf_atomic_insn;
>    enum bpf_token_type bpf_jmp_op = BPF_JEQ; /* Arbitrary.  */
>    enum bpf_token_type bpf_cast = BPF_CAST_U8; /* Arbitrary.  */