diff options
Diffstat (limited to 'lib/compiler/src/sys_core_bsm.erl')
| -rw-r--r-- | lib/compiler/src/sys_core_bsm.erl | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/lib/compiler/src/sys_core_bsm.erl b/lib/compiler/src/sys_core_bsm.erl index d7b26c3a56..62657933ee 100644 --- a/lib/compiler/src/sys_core_bsm.erl +++ b/lib/compiler/src/sys_core_bsm.erl @@ -44,6 +44,14 @@ function([{#c_var{name={F,Arity}}=Name,B0}|Fs], FsAcc, Ws0) -> {B,Ws} -> function(Fs, [{Name,B}|FsAcc], Ws) catch + throw:unsafe_bs_context_to_binary -> + %% Unsafe bs_context_to_binary (in the sense that the + %% contents of the binary will probably be wrong). + %% Disable binary optimizations for the entire function. + %% We don't generate an INFO message, because this happens + %% very infrequently and it would be hard to explain in + %% a comprehensible way in an INFO message. + function(Fs, [{Name,B0}|FsAcc], Ws0); Class:Error:Stack -> io:fwrite("Function: ~w/~w\n", [F,Arity]), erlang:raise(Class, Error, Stack) @@ -116,12 +124,66 @@ move_from_col(Pos, L) -> [Col|First] ++ Rest. bsm_do_an([#c_var{name=Vname}=V0|Vs0], Cs0, Case) -> + bsm_inner_context_to_binary(Cs0), Cs = bsm_do_an_var(Vname, Cs0), V = bsm_annotate_for_reuse(V0), Vs = core_lib:make_values([V|Vs0]), Case#c_case{arg=Vs,clauses=Cs}; bsm_do_an(_Vs, _Cs, Case) -> Case. +bsm_inner_context_to_binary([#c_clause{body=B}|Cs]) -> + %% Consider: + %% + %% foo(<<Length, Data/binary>>) -> %Line 1 + %% case {Data, Length} of %Line 2 + %% {_, 0} -> Data; %Line 3 + %% {<<...>>, 4} -> ... %Line 4 + %% end. + %% + %% No sub binary will be created for Data in line 1. The match + %% context will be passed on to the `case` in line 2. In line 3, + %% this pass inserts a `bs_context_to_binary` instruction to + %% convert the match context representing Data to a binary before + %% returning it. The problem is that the binary created will be + %% the original binary (including the matched out Length field), + %% not the tail of the binary as it is supposed to be. + %% + %% Here follows a heuristic to disable the binary optimizations + %% for the entire function if this code kind of code is found. + + case cerl_trees:free_variables(B) of + [] -> + %% Since there are no free variables in the body of + %% this clause, there can't be any troublesome + %% bs_context_to_binary instructions. + bsm_inner_context_to_binary(Cs); + [_|_]=Free -> + %% One of the free variables could refer to a match context + %% created by the outer binary match. + F = fun(#c_primop{name=#c_literal{val=bs_context_to_binary}, + args=[#c_var{name=V}]}, _) -> + case member(V, Free) of + true -> + %% This bs_context_to_binary instruction will + %% make a binary of the match context from an + %% outer binary match. It is very likely that + %% the contents of the binary will be wrong + %% (the original binary as opposed to only + %% the tail binary). + throw(unsafe_bs_context_to_binary); + false -> + %% Safe. This bs_context_to_binary instruction + %% will make a binary from a match context + %% defined in the body of the clause. + ok + end; + (_, _) -> + ok + end, + cerl_trees:fold(F, ok, B) + end; +bsm_inner_context_to_binary([]) -> ok. + bsm_do_an_var(V, [#c_clause{pats=[P|_],guard=G,body=B0}=C0|Cs]) -> case P of #c_var{name=VarName} -> |