[erlang-bugs] bogus 'unsafe variable' warning with try-else

[Anthony Ramine]

try file:read(F, 1024 * 1024) of
    {ok,Bin} -> binary_to_term(Bin)
after
    file:close(F)
end


Le 20 nov. 2014 à 12:49, Mikael Pettersson <mikpelinux@REDACTED> a écrit :

> The following, adapted from an example in the online Erlang
> Reference Manual, looks like a bug to me:
> 
>> cat bug.erl
> -module(bug).
> -compile(export_all).
> 
> termize_file(Name) ->
>  {ok,F} = file:open(Name, [read,binary]),
>  try
>    {ok,Bin} = file:read(F, 1024*1024)
>  after
>    file:close(F)
>  end,
>  binary_to_term(Bin).
>> erlc bug.erl
> bug.erl:11: variable 'Bin' unsafe in 'try' (line 6)
> 
> Unless I'm missing something, there is no way to reach the
> binary_to_term/1 call without successfully evaluating the
> {ok,Bin} = ... match expression; therefore the use is not
> unsafe.  If the file:read/2 call or the {ok,Bin} match fails,
> the after clause runs and the entire try expression fails,
> and the binary_to_term/1 is not reached.
> 
> Reproduced with 17.3 and r15b03-1.
> 
> Workaround: match on the value of the try itself:
> "{ok,Bin} = try file:read(...) after ... end".
> 
> /Mikael
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