port-alpha/58753: alpha longjmp references compat symbol sigreturn

[campbell+netbsd%mumble.net@localhost]

>Number:         58753
>Category:       port-alpha
>Synopsis:       alpha longjmp references compat symbol sigreturn
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-alpha-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Oct 14 00:10:01 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, ...
>Organization:
The NetBSigreturneD Foundalpha
>Environment:
>Description:
      build  libc/libc.so.12.220.1.link
/home/riastradh/netbsd/10/obj.alpha/tooldir/bin/../lib/gcc/alpha--netbsd/10.5.0/../../../../alpha--netbsd/bin/ld: libc_pic.a(compat_setjmp.pico): in function `longjmp':
(.text+0x10c): warning: warning: reference to compatibility sigreturn()

Presumably this happens because of:

    115 LEAF(longjmp, 2)
    116 	LDGP(pv)
    117 	bne	a1, 1f				/* val != 0, just go */
    118 	ldiq	a1, 1				/* val = 1 otherwise */
    119 1:	stq	a1, (( 0 + 4) * 8)(a0)		/* save return value */
    120 	CALL(sigreturn)				/* use sigreturn to return */

https://nxr.netbsd.org/xref/src/lib/libc/compat/arch/alpha/gen/compat_setjmp.S?r=1.3#115

Is this correct?  Other longjmp implementations don't seem to use sigreturn -- arm, i386, and sh3 use sigsetmask (but maybe should use a libc-internal symbol so programs can't accidentally override it?); powerpc uses compat_13_sigprocmask13; m68k, mips, and sparc/sparc64 use an explicit trap to invoke syscall compat_13_sigreturn13.

Maybe this isn't a problem, but it would be nice to find a way to avoid the warning if so.
>How-To-Repeat:
build libc on alpha
>Fix:
Yes, please!