Fix sigaltstack decoder
Fix sigaltstack decoder

strace used to hang when decoding sigaltstack called with invalid
stack_t pointers because of mishandling umove() return code.

* signal.c (print_stack_t): Handle unfetchable stack_t properly.
Change return type to void.
(sys_sigaltstack): Update print_stack_t() usage.

Reported-by: 983f0ce7afcff0aa78faed161d7ba6a14b951366@ucalgary.ca

lizh06/strace-plus,TeamExodus/external_strace,bigzz/strace_android,geekboxzone/mmallow_external_strace,kapdop/android_external_strace,geofft/strace,bigzz/strace_android,gcode-mirror/strace-plus,lizh06/strace-plus,lizh06/strace-plus,TeamExodus/external_strace,DirtyUnicorns/android_external_strace,lizh06/strace-plus,DirtyUnicorns/android_external_strace,gcode-mirror/strace-plus,TeamExodus/external_strace,DirtyUnicorns/android_external_strace,lkundrak/strace,geofft/strace,Distrotech/strace,cuviper/strace,Saruta/strace,bnoordhuis/strace,CyanogenMod/android_external_strace,Infinitive-OS/platform_external_strace,geekboxzone/lollipop_external_strace,Saruta/strace,TeamExodus/external_strace,geekboxzone/mmallow_external_strace,MonkeyZZZZ/platform_external_strace,pgbovine/strace-plus,gcode-mirror/strace-plus,CyanogenMod/android_external_strace,AOSP-YU/platform_external_strace,pombredanne/strace,Distrotech/strace,Yu-AndroidM/android_external_strace,Saruta/strace,CyanogenMod/android_external_strace,YUPlayGodDev/platform_external_strace,bnoordhuis/strace,lkundrak/strace,MonkeyZZZZ/platform_external_strace,pombredanne/strace,vrastogi/strace,jamel/strace-plus,kapdop/android_external_strace,Yu-AndroidM/android_external_strace,Infinitive-OS/platform_external_strace,lizh06/strace-plus,cuviper/strace,geekboxzone/mmallow_external_strace,pombredanne/strace,vrastogi/strace,YUPlayGodDev/platform_external_strace,pgbovine/strace-plus,bigzz/strace_android,geekboxzone/mmallow_external_strace,geofft/strace,jamel/strace-plus,geofft/strace,xin3liang/platform_external_strace,TeamExodus/external_strace,AOSP-YU/platform_external_strace,lkundrak/strace,cuviper/strace,geekboxzone/lollipop_external_strace,jamel/strace-plus,MonkeyZZZZ/platform_external_strace,YUPlayGodDev/platform_external_strace,DirtyUnicorns/android_external_strace,vrastogi/strace,geekboxzone/lollipop_external_strace,Yu-AndroidM/android_external_strace,Yu-AndroidM/android_external_strace,MonkeyZZZZ/platform_external_strace,jamel/strace-plus,Infinitive-OS/platform_external_strace,MonkeyZZZZ/platform_external_strace,lkundrak/strace,bnoordhuis/strace,Infinitive-OS/platform_external_strace,Distrotech/strace,xin3liang/platform_external_strace,xin3liang/platform_external_strace,pgbovine/strace-plus,android-ia/platform_external_strace,YUPlayGodDev/platform_external_strace,gcode-mirror/strace-plus,vrastogi/strace,Infinitive-OS/platform_external_strace,pgbovine/strace-plus,cuviper/strace,pombredanne/strace,android-ia/platform_external_strace,geofft/strace,xin3liang/platform_external_strace,cuviper/strace,geekboxzone/lollipop_external_strace,android-ia/platform_external_strace,vrastogi/strace,AOSP-YU/platform_external_strace,AOSP-YU/platform_external_strace,Distrotech/strace,kapdop/android_external_strace,pgbovine/strace-plus,kapdop/android_external_strace,kapdop/android_external_strace,android-ia/platform_external_strace,android-ia/platform_external_strace,jamel/strace-plus,Yu-AndroidM/android_external_strace,Distrotech/strace,bigzz/strace_android,gcode-mirror/strace-plus,CyanogenMod/android_external_strace,AOSP-YU/platform_external_strace,bnoordhuis/strace,DirtyUnicorns/android_external_strace,CyanogenMod/android_external_strace,YUPlayGodDev/platform_external_strace,geekboxzone/lollipop_external_strace,Saruta/strace,bigzz/strace_android,geekboxzone/mmallow_external_strace,Saruta/strace