| Adding a new Eiffel built-in routine | ![]() ![]() |
The following sections will describe step by step what needs to be done in order to add support for new built-in routines in the Eiffel compiler.
The first thing to do is to declare the name of the built-in feature and the name of its class. Let's assume that the built-in function foo and built-in procedure poo have been declared in class BAR. These feature and class names will have to be declared as follows in class ET_TOKEN_CONSTANTS if not already done:
feature -- Class names
bar_class_name: ET_CLASS_NAME
-- "BAR" class name
once
create {ET_IDENTIFIER} Result.make (capitalized_bar_name)
ensure
bar_class_name_not_void: Result /= Void
end
feature -- Feature names
foo_feature_name: ET_FEATURE_NAME
-- 'foo' feature name
once
create {ET_IDENTIFIER} Result.make (foo_name)
ensure
foo_feature_name_not_void: Result /= Void
end
poo_feature_name: ET_FEATURE_NAME
-- 'poo' feature name
once
create {ET_IDENTIFIER} Result.make (poo_name)
ensure
poo_feature_name_not_void: Result /= Void
end
feature -- Keyword and symbol names
capitalized_bar_name: STRING = "BAR"
-- Name of Eiffel class "BAR"
foo_name: STRING = "foo"
-- Name of Eiffel feature 'foo'
poo_name: STRING = "poo"
-- Name of Eiffel feature 'poo'
It is a good practice to keep these features in alphabetic order in their
respective feature clauses. Note that capitalized_bar_name,
foo_name and poo_name also
need to be listed in feature strings
from class ET_EIFFEL_SCANNER_SKELETON:
Again, try to keep them in alphabetic order in their respective sections.strings: DS_HASH_TABLE [INTEGER, STRING] -- Strings known by the current scanner, and the associated -- hash codes when they are used as identifier once ... -- Class names. Result.force_new (-1, tokens.capitalized_bar_name) ... -- Feature names. Result.force_new (-1, tokens.foo_name) ... Result.force_new (-1, tokens.poo_name) ... end
Each built-in feature is associated with a code which is made up of a class identifier and a feature identifier within this class. Still assuming that the built-in function foo and the built-in procedure poo have been declared in class BAR, the following features need to be declared in class ET_TOKEN_CODES if not already done:
where XX is the class identifier whose value should be different from all other builtin_*_class declared in this feature clause, and YY and ZZ are unique identifiers within the built-in features of this class. Note that the identifiers for the built-in functions should be listed first, followed by the identifiers for the built-in procedures.feature -- Built-in codes ... builtin_bar_class: NATURAL_8 = XX ... -- Code for classes of built-in features builtin_bar_foo: NATURAL_8 = YY -- Codes for built-in functions from class "BAR" builtin_bar_poo: NATURAL_8 = ZZ -- Codes for built-in procedures from class "BAR"
This convenience routine should also be added in class ET_DYNAMIC_FEATURE:
is_builtin_bar_class: BOOLEAN
-- Is current feature the built-in feature of class "BAR"?
do
Result := builtin_class_code = {ET_TOKEN_CODES}.builtin_bar_class
ensure
builtin: Result implies is_builtin
definition: Result = (builtin_class_code = {ET_TOKEN_CODES}.builtin_bar_class)
end
When features are flattened, the Eiffel compiler checks whether features declared as built-in are known and if they have the expected signature. This is done in class ET_BUILTIN_FEATURE_CHECKER. Let's assume that the feature foo is a built-in function with no argument and a result of type 'like Current', and the feature poo is a built-in procedure with one argument of type INTEGER. The following features need to be modified or added in class ET_BUILTIN_FEATURE_CHECKER:
check_builtin_feature_validity (a_feature: ET_EXTERNAL_ROUTINE) -- Check validity of built-in `a_feature', written in `current_class'. -- Set `has_fatal_error' if a fatal error occurred. require a_feature_not_void: a_feature /= Void local l_name: ET_CLASS_NAME do l_name := current_class.name if ... then ... elseif l_name.same_class_name (tokens.bar_class_name) then check_builtin_bar_feature_validity (a_feature) ... else -- Unknown built-in routine. a_feature.set_builtin_code (tokens.builtin_unknown) if unknown_builtin_reported then set_fatal_error error_handler.report_gvkbu1a_error (current_class, a_feature) end end end check_builtin_bar_feature_validity (a_feature: ET_EXTERNAL_ROUTINE) -- Check validity of built-in `a_feature' from class "BAR". -- Set `has_fatal_error' if a fatal error occurred. require a_feature_not_void: a_feature /= Void local l_builtin_features: DS_HASH_TABLE [TUPLE [arguments: detachable ARRAY [ET_TYPE]; type: detachable ET_TYPE; builtin_feature_code: NATURAL_8], ET_FEATURE_NAME] l_builtin_class_code: NATURAL_8 do l_builtin_class_code := tokens.builtin_bar_class builtin_features.search (l_builtin_class_code) if builtin_features.found then l_builtin_features := builtin_features.found_item else create l_builtin_features.make_map (...) l_builtin_features.set_key_equality_tester (feature_name_tester) builtin_features.force_last (l_builtin_features, l_builtin_class_code) -- Functions. ... register_builtin_feature (tokens.foo_feature_name, Void, tokens.like_current, tokens.builtin_bar_foo, l_builtin_features) ... -- Procedures. ... register_builtin_feature (tokens.poo_feature_name, <<current_universe.integer_type.type>>, Void, tokens.builtin_bar_poo, l_builtin_features) ... end check_expected_builtin_feature_validity (a_feature, l_builtin_class_code, l_builtin_features) end
Various examples with different combinations of argument and result types can be found in class ET_BUILTIN_FEATURE_CHECKER.
The Gobo Eiffel compiler uses the dynamic type sets of the target of the feature calls to implement dynamic binding and CAT-call checking. Each expression is associated with a dynamic type set which is then propagated when there is an assignment or argument passing. The dynamic type set of the 'Result' entity of built-in functions needs to be built. If it is only made up of exactly one type which is the declared type of the 'Result' entity of the built-in function, then nothing special needs to be done. The default implementation will take care of this case. On the other hand, if the dynamic type set is more complicated or if the built-in feature calls internally another feature whose dynamic type sets need to be updated as well (for example feature twin calls feature copy), then the following code needs to appear in class ET_DYNAMIC_TYPE_BUILDER:
feature {NONE} -- Feature validity
check_external_builtin_function_validity (a_feature: ET_EXTERNAL_FUNCTION)
-- Check validity of `a_feature'.
-- `a_feature' is a built-in function.
-- Set `has_fatal_error' if a fatal error occurred.
require
a_feature_not_void: a_feature /= Void
a_feature_is_builtin: a_feature.is_builtin
builtin_feature_known: not a_feature.is_builtin_unknown
do
inspect a_feature.builtin_class_code
...
when {ET_TOKEN_CODES}.builtin_bar_class then
inspect a_feature.builtin_feature_code
when {ET_TOKEN_CODES}.builtin_bar_foo then
report_builtin_bar_foo (a_feature)
else
report_builtin_function (a_feature)
end
...
else
report_builtin_function (a_feature)
end
end
feature {NONE} -- Built-in features
report_builtin_bar_foo (a_feature: ET_EXTERNAL_FUNCTION)
-- Report that built-in feature 'BAR.foo' is being analyzed.
require
no_error: not has_fatal_error
a_feature_not_void: a_feature /= Void
local
l_result_type: ET_DYNAMIC_TYPE
do
if current_type = current_dynamic_type.base_type then
...
l_result_type := result_type_set.static_type
propagate_builtin_result_dynamic_types (l_result_type, current_dynamic_feature)
...
end
end
By default, nothing needs to be done for built-in procedures. But there are some
special cases when the built-in procedure will call internally another feature or
will have an effect on the dynamic type set of some entities (for example in class
SPECIAL, the procedure put will
have an effect on the dynamic type set of item).
In this case, code similar to the one above will be needed for these built-in
procedures. Examples can be found in class ET_DYNAMIC_TYPE_BUILDER.
The last thing to do is to make sure that the C code of the built-in feature is properly generated. Still assuming that foo is a built-in function and poo is a built-in procedure declared in class BAR. Then the following code needs to appear in class ET_C_GENERATOR:
feature {NONE} -- Feature generation
print_external_builtin_function_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in function.
require
a_feature_not_void: a_feature /= Void
a_feature_is_function: a_feature.is_function
a_feature_is_builtin: a_feature.is_builtin
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_class_code
...
when {ET_TOKEN_CODES}.builtin_bar_class then
print_external_builtin_bar_function_body (a_feature)
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
print_external_builtin_bar_function_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in function introduced in class "BAR".
require
a_feature_not_void: a_feature /= Void
a_feature_is_function: a_feature.is_function
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: current_feature.is_builtin_bar_class
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_feature_code
...
when {ET_TOKEN_CODES}.builtin_bar_foo then
print_builtin_bar_foo_body (a_feature)
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
print_external_builtin_procedure_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in procedure.
require
a_feature_not_void: a_feature /= Void
a_feature_is_procedure: a_feature.is_procedure
a_feature_is_builtin: a_feature.is_builtin
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_class_code
...
when {ET_TOKEN_CODES}.builtin_bar_class then
print_external_builtin_bar_procedure_body (a_feature)
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
print_external_builtin_bar_procedure_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in procedure introduced in class "BAR".
require
a_feature_not_void: a_feature /= Void
a_feature_is_procedure: a_feature.is_procedure
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: current_feature.is_builtin_bar_class
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_feature_code
...
when {ET_TOKEN_CODES}.builtin_bar_poo then
print_builtin_bar_poo_body (a_feature)
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
feature {NONE} -- Built-in feature generation
print_builtin_bar_foo_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of `a_feature' corresponding
-- to built-in feature 'BAR.foo'.
require
a_feature_not_void: a_feature /= Void
valid_feature: current_feature.static_feature = a_feature
do
...
end
print_builtin_bar_poo_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of `a_feature' corresponding
-- to built-in feature 'BAR.poo'.
require
a_feature_not_void: a_feature /= Void
valid_feature: current_feature.static_feature = a_feature
do
...
end
In some cases, the C code can be inlined. This is when the call to the C function
can be avoided by calling the C code directly. In that case the code above in class
ET_C_GENERATOR can be changed by replacing
print_builtin_bar_foo_body by print_builtin_bar_foo_call
and print_builtin_bar_poo_body by print_builtin_bar_poo_call,
and by modifying features print_external_builtin_bar_function_body
and print_external_builtin_bar_procedure_body
as follows:
feature {NONE} -- Feature generation
print_external_builtin_bar_function_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in function introduced in class "BAR".
require
a_feature_not_void: a_feature /= Void
a_feature_is_function: a_feature.is_function
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: current_feature.is_builtin_bar_class
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_feature_code
...
when {ET_TOKEN_CODES}.builtin_bar_foo then
fill_call_formal_arguments (a_feature)
print_indentation_assign_to_result
print_builtin_bar_foo_call (current_feature, current_type, False)
print_semicolon_newline
call_operands.wipe_out
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
print_external_builtin_bar_procedure_body (a_feature: ET_EXTERNAL_ROUTINE)
-- Print to `current_file' the body of built-in feature `a_feature'.
-- `a_feature' is a built-in procedure introduced in class "BAR".
require
a_feature_not_void: a_feature /= Void
a_feature_is_procedure: a_feature.is_procedure
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: current_feature.is_builtin_bar_class
valid_feature: current_feature.static_feature = a_feature
do
inspect a_feature.builtin_feature_code
...
when {ET_TOKEN_CODES}.builtin_bar_poo then
fill_call_formal_arguments (a_feature)
print_builtin_bar_poo_call (current_feature, current_type, False)
call_operands.wipe_out
...
else
-- Internal error: unknown built-in feature.
-- This error should already have been reported in ET_FEATURE_FLATTENER.
set_fatal_error
error_handler.report_giaaa_error
end
end
feature {NONE} -- Query call generation
print_builtin_query_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call to query `a_feature' (static binding).
-- `a_feature' is a built-in feature.
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
-- Note that the result of the query is not adapted to match the kind
-- of result type expected by the caller. It is recommended to use
-- `print_adapted_query_call' whenever possible.
require
a_feature_not_void: a_feature /= Void
a_feature_is_query: a_feature.result_type_set /= Void
a_feature_is_builtin: a_feature.is_builtin
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
inspect a_feature.builtin_class_code
...
when {ET_TOKEN_CODES}.builtin_bar_class then
print_builtin_bar_query_call (a_feature, a_target_type, a_check_void_target)
...
else
print_non_inlined_query_call (a_feature, a_target_type, a_check_void_target)
end
end
print_builtin_bar_query_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call to query `a_feature' (static binding).
-- `a_feature' is a built-in feature introduced in class "BAR".
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
-- Note that the result of the query is not adapted to match the kind
-- of result type expected by the caller. It is recommended to use
-- `print_adapted_query_call' whenever possible.
require
a_feature_not_void: a_feature /= Void
a_feature_is_query: a_feature.result_type_set /= Void
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: a_feature.is_builtin_bar_class
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
inspect a_feature.builtin_feature_code
...
when {ET_TOKEN_CODES}.builtin_bar_foo then
print_builtin_bar_foo_call (a_feature, a_target_type, a_check_void_target)
...
else
print_non_inlined_query_call (a_feature, a_target_type, a_check_void_target)
end
end
feature {NONE} -- Procedure call generation
print_builtin_procedure_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call to procedure `a_feature' (static binding).
-- `a_feature' is a built-in feature.
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
require
a_feature_not_void: a_feature /= Void
a_feature_is_builtin: a_feature.is_builtin
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
inspect a_feature.builtin_class_code
...
when {ET_TOKEN_CODES}.builtin_bar_class then
print_builtin_bar_procedure_call (a_feature, a_target_type, a_check_void_target)
...
else
print_non_inlined_procedure_call (a_feature, a_target_type, a_check_void_target)
end
end
print_builtin_bar_procedure_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call to procedure `a_feature' (static binding).
-- `a_feature' is a built-in feature introduced in class "BAR".
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
require
a_feature_not_void: a_feature /= Void
a_feature_is_builtin: a_feature.is_builtin
a_feature_is_builtin_bar: a_feature.is_builtin_bar_class
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
inspect a_feature.builtin_feature_code
when builtin_bar_poo then
print_builtin_bar_poo_call (a_feature, a_target_type, a_check_void_target)
...
else
print_non_inlined_procedure_call (a_feature, a_target_type, a_check_void_target)
end
end
feature {NONE} -- Built-in feature generation
print_builtin_bar_foo_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call (static binding) to `a_feature'
-- corresponding to built-in feature 'BAR.foo'.
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
require
a_feature_not_void: a_feature /= Void
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
...
end
print_builtin_bar_poo_call (a_feature: ET_DYNAMIC_FEATURE; a_target_type: ET_DYNAMIC_TYPE; a_check_void_target: BOOLEAN)
-- Print to `current_file' a call (static binding) to `a_feature'
-- corresponding to built-in feature 'BAR.poo'.
-- `a_target_type' is the dynamic type of the target.
-- `a_check_void_target' means that we need to check whether the target is Void or not.
-- Operands can be found in `call_operands'.
require
a_feature_not_void: a_feature /= Void
a_target_type_not_void: a_target_type /= Void
call_operands_not_empty: not call_operands.is_empty
do
...
end
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Copyright © 2010-2017, Eric Bezault mailto:ericb@gobosoft.com http://www.gobosoft.com Last Updated: 15 April 2017 |
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