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There is currently no zero-cost way to silence the warning
"the result of the expression is ignored", which is issued
for code such as:
list_to_integer(S),
ok
Such code can be useful for assertions or input validation.
Teach the compiler to silence the warning for expressions
that are explicitly assigned to to the "_" variable,
such as:
_ = list_to_integer(S),
ok
Implement it by having the v3_core pass annotate calls in
Core Erlang like this:
let <_> = ( call 'erlang':'list_to_integer'(S) -| ['result_not_wanted'] )
in 'ok'
and modifiy sys_core_fold to suppress the warning for any call
having the annotation.
We deliberately do not make it possible to silence the warnings
for expressions like:
{build,an,unnecessary,term}, ok
or
is_list(L), ok
because we don't know of any real-world scenarios in which that would
be useful.
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A function_clause exception is generated by jumping to a func_info/3
instruction at the beginning of the function. The x registers are
assumed to contain the arguments for the function. That means
that a func_info/3 instruction copied from another function
(or even from the same function if not at the top level) will
not work, so it must be replaced with an instruction that
generates a case_clause exception.
In Core Erlang, a func_info/3 instruction is represented as
a the primop match_fail({function_clause,Arg1,...ArgN}).
The current mechanism that is supposed to replace the
primop match_fail(function_clause) with match_fail(case_clause)
will fail to do that in the following circumstances:
1. If the inliner has inlined a function into itself.
Fix that by having the inliner clear the function_name annotations
on all match_fail primops in functions that are inlined. (To simplify
doing that, the annotation is now on the primop node itself and not on
the 'function_clause' atom inside it.)
2. If the inliner has rewritten the tuple node in the primop node
to a literal (when inlining a function call with literal arguments),
v3_kernel would not recognize the match_fail(function_clause) primop
and would not rewrite it. Fix it by making v3_kernel smarter.
Also simplify the "old" inliner (sys_core_inline) to only clear
the function_name annotations instead of rewriting function_clause
execptions to case_clause execptions itself.
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The no_binaries option terminates the compiler with an error
if any bit syntax is used in the module being compiled.
(It used to be implied by the removed r11 option.)
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* ks/compiler:
compiler: keep line numbers for attributes
compiler Makefile: alphabetize module names
compile.erl: eliminate compiler warning
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In the future, we might want to generate warnings
for attributes, referring to them with line numbers.
sys_pre_expand used to replace line number for attributes
with 0. Change sys_pre_expand to retain the real line
number.
v3_core used to throw away the line numbers. Change
v3_core so that it retains the line numbers in annotations.
While at it, do some tidying as suggested by tidier.
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