Stefan Schulze Frielinghaus via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
> While bootstrapping GCC on S/390 the following warning/error is raised:
>
> gcc/var-tracking.c:10239:34: error: 'pre' may be used uninitialized in this
> function [-Werror=maybe-uninitialized]
> 10239 | VTI (bb)->out.stack_adjust += pre;
> | ^
>
> The lines of interest are:
>
> HOST_WIDE_INT pre, post = 0;
> // ...
> if (!frame_pointer_needed)
> {
> insn_stack_adjust_offset_pre_post (insn, &pre, &post);
> // ...
> }
>
> // ...
> adjust_insn (bb, insn);
>
> if (!frame_pointer_needed && pre)
> VTI (bb)->out.stack_adjust += pre;
>
> Both if statements depend on global variable frame_pointer_needed. In
> function
> insn_stack_adjust_offset_pre_post local variable pre is initialized. The
> problematic part is the function call between both if statements. Since
> adjust_insn also calls functions which are defined in a different compilation
> unit, we are not able to prove that global variable frame_pointer_needed is
> not
> altered by adjust_insn and its siblings. Thus we must assume that
> frame_pointer_needed may be true before the call and false afterwards which
> renders the warning true (admitted the location hint is not totally perfect).
> By initialising pre we silence the warning.
>
> Bootstrapped and regtested on S/390. Ok for master?
>
> gcc/ChangeLog:
>
> 2020-04-28 Stefan Schulze Frielinghaus <stefa...@linux.ibm.com>
>
> * var-tracking.c (vt_initialize): Initialize local variable pre.
OK, thanks.
Richard
