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1156-sys_core_fold-Eliminate-crash-in-beam_kern...
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File 1156-sys_core_fold-Eliminate-crash-in-beam_kernel_to_ssa-.patch of Package erlang
From 5076069ff1278ba7a511f8cdd449d2718abfa278 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?John=20H=C3=B6gberg?= <john@erlang.org> Date: Tue, 3 Jan 2023 15:30:49 +0100 Subject: [PATCH] sys_core_fold: Eliminate crash in beam_kernel_to_ssa, again --- lib/compiler/src/sys_core_fold.erl | 44 +++++------ lib/compiler/test/core_fold_SUITE.erl | 109 ++++++++++++++++++++------ 2 files changed, 101 insertions(+), 52 deletions(-) diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index 206f39e190..ea3d0b7f6a 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -2216,32 +2216,24 @@ move_let_into_expr(#c_let{vars=InnerVs0,body=InnerBody0}=Inner0, OuterBody = body(OuterBody0, ScopeSub), - {InnerVs,Sub} = var_list(InnerVs0, Sub0), - InnerBody = body(InnerBody0, Sub), - Inner = case will_fail(OuterBody) of - true -> - %% - %% Avoid creating potentially unsafe code that - %% depends on another iteration of the outer - %% fixpoint loop to clean up. If <OuterBody> - %% consists of nested lets, we may run out of - %% iterations before the unsafe code is - %% eliminated. - %% - %% let <InnerVars> = let <OuterVars> = <Arg> - %% in <OuterBody> - %% in <InnerBody> - %% - %% ==> - %% - %% let <OuterVars> = <Arg> - %% in <OuterBody> - %% - OuterBody; - false -> - Inner0#c_let{vars=InnerVs,arg=OuterBody,body=InnerBody} - end, - Outer#c_let{vars=OuterVs,arg=Arg,body=Inner}; + case will_fail(OuterBody) of + true -> + %% + %% Avoid creating potentially unsafe code that + %% depends on another iteration of the outer + %% fixpoint loop to clean up. If <OuterBody> + %% consists of nested lets, we may run out of + %% iterations before the unsafe code is + %% eliminated. + %% + Inner0; + false -> + {InnerVs,Sub} = var_list(InnerVs0, Sub0), + InnerBody = body(InnerBody0, Sub), + + Inner = Inner0#c_let{vars=InnerVs,arg=OuterBody,body=InnerBody}, + Outer#c_let{vars=OuterVs,arg=Arg,body=Inner} + end; move_let_into_expr(#c_let{vars=Lvs0,body=Lbody0}=Let, #c_case{arg=Cexpr0,clauses=[Ca0|Cs0]}=Case, Sub0) -> case not is_failing_clause(Ca0) andalso diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl index de2b46e7a8..c5f8037ed4 100644 --- a/lib/compiler/test/core_fold_SUITE.erl +++ b/lib/compiler/test/core_fold_SUITE.erl @@ -701,41 +701,98 @@ do_receive_effect() -> {} = receive _ -> {} = {} end. nested_lets(_Config) -> - {'EXIT',{{case_clause,ok},_}} = catch nested_lets_gh_6572(<<42>>), + {'EXIT',{{case_clause,ok},_}} = catch nested_lets_1(<<42>>), + {'EXIT',{badarith,_}} = catch nested_lets_2(id(0), id(0)), ok. -nested_lets_gh_6572(<<X>>) -> +%% GH-6572: Deeply nested `let` expressions caused `sys_core_fold` to generate +%% unsafe code that it would attempt to fix up later. Unfortunately it did so +%% through a limited fixpoint iteration, and would leak said code once the +%% limit was hit. +nested_lets_1(<<X>>) -> Y = case ok of X -> - true = (ok > ((Y = _) = -1)), + true = (ok > (Y = -1)), <<>> = {id( - << - (ok - ok), - (bnot ok), - (nested_lets_gh_6572_f() band ok), - (nested_lets_gh_6572_f()), - (not ok), - (ok or nested_lets_gh_6572_f()), - (id( - id( - << - (id( - << - (id( - <<0 || _ <- []>> - )) - >> - ) * ok) - >> - ) - )) - >> - )} + << + (ok - ok), + (bnot ok), + (nested_lets_1_f() band ok), + (nested_lets_1_f()), + (not ok), + (ok or nested_lets_1_f()), + (id( + id( + << + (id( + << + (id( + <<0 || _ <- []>> + )) + >> + ) * ok) + >> + ) + )) + >> + )} end. -nested_lets_gh_6572_f() -> +nested_lets_1_f() -> + ok. + +%% GH-6612: A variant of GH-6572 that slipped through the initial fix. +nested_lets_2(X, 0) -> + try + 0 = { + _ = 0 + 0, + Z = bnot ok, + {(_ = ok), (_ = X)}#{ok => ok}, + ok + + (nested_lets_2_f( + ok + + nested_lets_2_f( + ok + + (nested_lets_2_f( + (Y = + -nested_lets_2_f( + #{ + (ok + + (ok + + nested_lets_2_f( + case + try ok of + _ -> + fun(_) -> + ok + end + after + ok + end + of + #{} -> + ok + end + ))) => ok + } > ok + )) + ) + ok) + ) > + ok + )) + } + of + _ -> + Z; + _ -> + Y + after + ok + end. + +nested_lets_2_f(_) -> ok. %%% Common utility functions. -- 2.35.3
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