Eliminate crash because of unsafe delaying of sub-binary creation

The following code would fail to compile:

decode(<<Code/integer, Bin/binary>>) ->
    <<C1/integer, B1/binary>> = Bin,
    case C1 of
	X when X =:= 1 orelse X =:= 2 ->
	    Bin2 = <<>>;
	_ ->
	    Bin2 = B1
    end,
    case Code of
	1 -> decode(Bin2);
	_ -> Bin2
    end.

The error message would be:

t: function decode/1+28:
  Internal consistency check failed - please report this bug.
  Instruction: return
  Error:       {match_context,{x,0}}:

The beam_bsm pass would delay the creation of a sub-binary when it was
unsafe to do so. The culprit was the btb_follow_branch/3 function that
for performance reasons cached labels that had already been checked.
The problem was the safety of a label also depends on the contents
of the registers. Therefore, the key for caching needs to be both
the label and the register contents.

Reported-by: José Valim

0 files changed, 0 insertions, 0 deletions