Martin Liška <mli...@suse.cz> writes:
> It's the warning I see every time I build GCC:
>
> In file included from /home/marxin/Programming/gcc/gcc/coretypes.h:478,
> from /home/marxin/Programming/gcc/gcc/expmed.cc:26:
> In function ‘poly_uint16 mode_to_bytes(machine_mode)’,
> inlined from ‘typename if_nonpoly<typename T::measurement_type>::type
> GET_MODE_SIZE(const T&) [with T = scalar_int_mode]’ at
> /home/marxin/Programming/gcc/gcc/machmode.h:647:24,
> inlined from ‘rtx_def* emit_store_flag_1(rtx, rtx_code, rtx, rtx,
> machine_mode, int, int, machine_mode)’ at
> /home/marxin/Programming/gcc/gcc/expmed.cc:5728:56:
> /home/marxin/Programming/gcc/gcc/machmode.h:550:49: warning: ‘*(unsigned
> int*)((char*)&int_mode + offsetof(scalar_int_mode, scalar_int_mode::m_mode))’
> may be used uninitialized [-Wmaybe-uninitialized]
> 550 | ? mode_size_inline (mode) : mode_size[mode]);
> | ^~~~
> /home/marxin/Programming/gcc/gcc/expmed.cc: In function ‘rtx_def*
> emit_store_flag_1(rtx, rtx_code, rtx, rtx, machine_mode, int, int,
> machine_mode)’:
> /home/marxin/Programming/gcc/gcc/expmed.cc:5657:19: note: ‘*(unsigned
> int*)((char*)&int_mode + offsetof(scalar_int_mode, scalar_int_mode::m_mode))’
> was declared here
> 5657 | scalar_int_mode int_mode;
> | ^~~~~~~~
>
> Can we please mitigate it?
>
> gcc/ChangeLog:
>
> * expmed.cc (emit_store_flag_1): Mitigate -Wmaybe-uninitialized
> warning.
Not a strong objection, but TBH I'd rather we didn't work around false
positives like this.
Richard
> ---
> gcc/expmed.cc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/expmed.cc b/gcc/expmed.cc
> index 41738c1efe9..f23d63471ea 100644
> --- a/gcc/expmed.cc
> +++ b/gcc/expmed.cc
> @@ -5654,7 +5654,7 @@ emit_store_flag_1 (rtx target, enum rtx_code code, rtx
> op0, rtx op1,
>
> /* If we are comparing a double-word integer with zero or -1, we can
> convert the comparison into one involving a single word. */
> - scalar_int_mode int_mode;
> + scalar_int_mode int_mode = {};
> if (is_int_mode (mode, &int_mode)
> && GET_MODE_BITSIZE (int_mode) == BITS_PER_WORD * 2
> && (!MEM_P (op0) || ! MEM_VOLATILE_P (op0)))
