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modules. (Thanks to Jebu Ittiachen.)
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* cf/compile_warning_as_error:
Add option -Werror in erlc(1)
compile: add flag warnings_as_errors to treat warnings as errors
compile.erl: remove trailing whitespace
OTP-8382 The -Werror option for erlc and the compiler option
warnings_as_errors will cause warnings to be treated as errors.
(Thanks to Christopher Faulet.)
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With this flag, warnings are treated as errors, like gcc flag '-Werror'.
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* bg/compiler-beam_validator:
beam_validator: fix incorrect assumptions about GC guard BIFs
OTP-8378 In rare circumstances when using garbaging collecting guard BIFs,
the validation pass (beam_validator) would signal that the code
was unsafe, when it in fact was correct. (Thanks to Kiran
Khaladkar.)
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The beam_validator pass incorrectly assumes that a GC guard
BIF (such as length/1) may first do a garbage collection
and then fail. That assumption is not correct (guards BIF
only do garbage collection when it is known that the BIF
call will succeed), and will cause the compiler to reject
valid programs.
Modify the beam_validator to assume that if the branch is
taken for a gc_bif instruction, all registers are unchanged
and no garbage collection has occurred. Also add a comment
in the emulator about that assumption.
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* bg/on_load:
Test on_load functions that don't return 'ok'
Change the expected return value for on_load functions
OTP-8339 The expected return value for an on_load function has been
changed. (See the section about code loading in the Reference
manual.)
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An on_load function is supposed to return 'true' to indicate
that the module should be loaded, and 'false' if it should be
unloaded. But returning any other term, as well as causing an
exception, will also unload the module.
Since we don't like boolean values mixed with other values,
change the expected return value as follows:
* If 'ok' is returned, the module will remain loaded and become
callable.
* If any other value is returned (or an exception is generated),
the module will be unloaded. Also, if the returned value is
not an atom, send a warning message to the error_logger
(using error_logger:warning_msg/2).
The new interpretation of the return value means that an on_load
function can now directly return the return value from
erlang:load_nif/2.
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The following code (by Simon Cornish)
bad(XDo1, XDo2, Do3) ->
Do1 = (XDo1 =/= []),
Do2 = (XDo2 =/= []),
CH1 = if Do1 == true;
Do1 == false,Do2==false,Do3 == blah ->
ch1;
true ->
no
end,
CH2 = if Do1 == true;
Do1 == false,Do2==false,Do3 == xx ->
ch2;
true ->
no
end,
{CH1,CH2}.
is optimized by beam_bool even though the optimization is not
safe. The trouble is that an assignment to {y,0} no longer
occurs on all paths leading to its use.
The bug is in dst_regs/2 which is supposed to return a set
of all registers assigned in a code block, but it ignores
registers assigned in 'move' instructions.
Fix the bug by taking 'move' instructions into account. This change
is safe since it can only cause more registers to be added
to the MustBeKilled and MustBeUnused sets in ensure_opt_safe/6,
which means that it can only cause the optimization to be turned
off for code that used to be optimized.
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The following code crashes beam_bool:
bad(XDo1, XDo2, Do3) ->
Do1 = (XDo1 =/= []),
Do2 = (XDo2 =/= []),
if Do1 =:= true;
Do1 =:= false, Do2 =:= false, Do3 =:= delete ->
no
end.
(Reported by Simon Cornish; minimized by Kostis Sagonas.)
For the moment fix the bug in the simplest and safest way possible
(basically, instead of crashing just don't do the optimization).
In a future major release (e.g. R14), the following improvements
could be considered:
* In beam_bool, it should be possible to move the Do1 and Do2
expressions to the pre-block and still optimize the expression
in the 'if' statement.
* In sys_core_fold, it should be possible to eliminate the
try/catch around the guard expression in the 'if', because
none of the guard tests can actually fail.
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