This doesn't seem too dreadful so far (partly because nothing is using
this machinery for something important, and partly because we're parsing
the vector from a file with known length), but fix it anyway.
#define CAP__SWITCH(type, ubranch, slot) \
case type: probed.slot = a->value.ubranch; break;
WANTAUX(CAP__SWITCH)
#define CAP__SWITCH(type, ubranch, slot) \
case type: probed.slot = a->value.ubranch; break;
WANTAUX(CAP__SWITCH)
+ case AT_NULL: goto clean;