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beam_validator would complain that x(1) is uninitialized
in a test_heap instruction when attempting to compile
the following code with sys_core_fold turned off:
foo(M) when not (M#{true := 0}); [M] ->
ok.
Simplified, the generated BEAM assembly code looked like
this:
test is_map BadMap x(0)
put_map_exact Fail x(0) => x(1) ...
jump BooleanStuff
BadMap:
move ok => x(1)
jump Fail
BooleanStuff:
...
move Boolean => x(2)
jump Build
Fail:
move false => x(2)
Build:
test_heap 2 3 %% x(0), x(1), x(2) must be live.
...
That is, if put_map_exact failed, control would transfer
to the label Fail without initializing x(1).
Fix that by making sure that x(1) is initilized even if
put_map_exact fails:
test is_map BadMap x(0)
put_map_exact BadLbl x(0) => x(1) ...
jump OkLbl
BadLbl:
move ok => x(1)
jump Fail
OkLbl:
jump BooleanStuff
BadMap:
move ok => x(1)
jump Fail
BooleanStuff:
...
move Boolean => x(2)
jump Build
Fail:
move false => x(2)
Build:
test_heap 2 3 %% x(0), x(1), x(2) must be live.
...
Note that this situation is rare, and that other optimization passes
(beam_dead and beam_jump in particular) will clean up this mess.
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Generate code that not only is safe, but can easily be seen by
beam_validator to be safe.
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* maint:
Fix crash when attempting to update a fun as if it were a map
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The following example would cause an internal consistency
failure in the compiler:
f() -> ok.
update() -> (fun f/0)#{u => 42}.
The reason is that internally, v3_core will (incorrectly)
rewrite update/0 to code similar to this:
update() ->
if
is_map(fun f/0) ->
maps:update(u, 42, fun f/0)
end.
Since funs are not allowed to be created in guards, incorrect and
unsafe code would be generated.
It is easy to fix the bug. There already is a is_valid_map_src/1
function in v3_core that tests whether the argument for the map update
operation can possibly be a valid map. A fun is represented as a
variable with a special name in Core Erlang, so it would not be
recognized as unsafe. All we'll need to do to fix the bug is to look
closer at variables to ensure they don't represent funs. That will
ensure that the code is rewritten in the correct way:
update() ->
error({badmap,fun f/0})
end.
Reported-by: Thomas Arts
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According to EEP-43 for maps, a 'badmap' exception should be
generated when an attempt is made to update non-map term such as:
<<>>#{a=>42}
That was not implemented in the OTP 17.
José Valim suggested that we should take the opportunity to
improve the errors coming from map operations:
http://erlang.org/pipermail/erlang-questions/2015-February/083588.html
This commit implement better errors from map operations similar
to his suggestion.
When a map update operation (Map#{...}) or a BIF that expects a map
is given a non-map term, the exception will be:
{badmap,Term}
This kind of exception is similar to the {badfun,Term} exception
from operations that expect a fun.
When a map operation requires a key that is not present in a map,
the following exception will be raised:
{badkey,Key}
José Valim suggested that the exception should be
{badkey,Key,Map}. We decided not to do that because the map
could potentially be huge and cause problems if the error
propagated through links to other processes.
For BIFs, it could be argued that the exceptions could be simply
'badmap' and 'badkey', because the bad map and bad key can be found in
the argument list for the BIF in the stack backtrace. However, for the
map update operation (Map#{...}), the bad map or bad key will not be
included in the stack backtrace, so that information must be included
in the exception reason itself. For consistency, the BIFs should raise
the same exceptions as update operation.
If more than one key is missing, it is undefined which of
keys that will be reported in the {badkey,Key} exception.
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To be sure that the compiler and BEAM virtual machine correctly
handles literals maps, we must test it.
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where key 1 is less than key 1.0
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A map key in a pattern would be incorrectly pretty-printed.
As an example, the pattern in:
x() ->
#{ #{ a => 3 } := 42 } = X.
would be pretty-printed as:
<~{~<~{~<'a',3>}~,42>}~
instead of:
<~{~<~{::<'a',3>}~,42>}~
When this problem has been corrected, the workaround for it in
cerl:ann_c_map/3 can be removed. The workaround was not harmless,
as it would cause the following map update to incorrectly succeed:
(#{})#{a:=1}
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Map keys with large (non literal) binary keys must fail.
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Increases coverage.
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Coverage removed by literals.
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Reported-by: José Valim
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* nox/maps-beam_jump-put_map:
Properly collect labels in put_map instructions in beam_jump
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* nox/maps-beam_jump:
Properly check label use in get_map_elements in beam_jump
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* nox/maps-v3_codegen-sort-nil-keys:
Properly sort map pairs in v3_codegen
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Reported-by: Ulf Norell
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Reported-by: Ulf Norell
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The Kernel instructions were not properly ordered when compiling maps with
complex values mixed in assoc and exact pairs.
Reported-by: Ulf Norell
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Literal nil values aren't tagged tuple but the bare atom nil.
The function lists:sort/2 expects the passed function to return true if the first
element is less than or equal to the second, not strictly less than. The original
base clause is changed accordingly.
Reported-by: Ulf Norell
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* nox/maps-fix-beam_bool-put_map:
Properly collect labels in put_map instructions in beam_bool
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* nox/maps-expand-update:
Fix expansion of map update arguments
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Reported-by: Ulf Norell
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Reported-by: José Valim
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* egil/compiler/maps-fix-sys_core_fold:
compiler: Fix sys_core_fold let optimization
compiler: Add debug listing after sys_core_fold
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* egil/compiler/maps-fix-codegen:
compiler: Fix codegen multiple updates for Maps
erts,compiler: Correct and amend tests for Maps
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Map variable was not covered and faulty optimization could occur.
Ex.
t() ->
M0 = id(#{ "a" => 1 }),
#{ "a" := _ } = M0,
M0#{ "a" := b }.
M0 was lost in let expression optimization.
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Faulty test for maps update
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M#{ key := V } should fail when M is not a Map
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