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erts: Disable unsafe optimization in bs_append #9372

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Merged
merged 1 commit into from
Feb 12, 2025
Merged

erts: Disable unsafe optimization in bs_append #9372

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12 changes: 0 additions & 12 deletions erts/emulator/beam/erl_bits.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1479,14 +1479,6 @@ erts_bs_append_checked(Process* c_p, Eterm* reg, Uint live,
}
}

if (build_size_in_bits == 0) {
if (HeapWordsLeft(c_p) < extra_words) {
(void) erts_garbage_collect(c_p, extra_words, reg, live+1);
bin = reg[live];
}
return bin;
}

if((ERTS_UINT_MAX - build_size_in_bits) < erts_bin_offset) {
c_p->fvalue = am_size;
c_p->freason = SYSTEM_LIMIT;
Expand Down Expand Up @@ -1573,10 +1565,6 @@ erts_bs_append_checked(Process* c_p, Eterm* reg, Uint live,
}
}

if (build_size_in_bits == 0) {
return bin;
}

if((ERTS_UINT_MAX - build_size_in_bits) < erts_bin_offset) {
c_p->fvalue = am_size;
c_p->freason = SYSTEM_LIMIT;
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8 changes: 6 additions & 2 deletions erts/emulator/test/bs_construct_SUITE.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -553,9 +553,13 @@ do_something() ->

append_empty_is_same(Config) when is_list(Config) ->
NonWritableBin = <<"123">>,
true = erts_debug:same(NonWritableBin, append(NonWritableBin, <<>>)),

%% Should use erts_debug:same/2, but this was disabled in PR-9372
%% (ERIERL-1177) because the optimization was unsafe.
true = NonWritableBin =:= append(NonWritableBin, <<>>),
WritableBin = <<(id(<<>>))/binary,0,1,2,3,4,5,6,7>>,
true = erts_debug:same(WritableBin, append(WritableBin, <<>>)),
true = WritableBin =:= append(WritableBin, <<>>),

ok.

append(A, B) ->
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