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generic_macros.h
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#pragma region _Generic Macros
// ____ _ ______ _ _ ____ _ __ _
// / ___} (_) | ____} | | (_) / __ \ | | | |(_)
// | | ___ ___ _ __ ___ _ __ _ ___ | |__ _ _ _ __ ___| |_ _ ___ _ __ | | | |_ _____ _ __ | | ___ __ _ __| | _ _ __ __ _
// | |{__ |/ _ \ '_ \ / _ \ '__} |/ __| | __} | | | '_ \ / __} __} |/ _ \| '_ \ | | | \ \ / / _ \ '_ }| |/ _ \ / _` |/ _` || | '_ \ / _` |
// | |__j | __/ | | | __/ | | | (__ | | | |_| | | | | (__| l_| | (_) | | | | | l__| |\ V / __/ | | | (_) | (_| | (_| || | | | | (_| |
// \____/ \___}_l l_l\___}_l l_l\___| l_l \__,_l_l l_l\___}\__}_l\___/l_l l_l \____/ \_/ \___}_l l_l\___/ \__,_l\__,_l|_|_| |_|\__, |
// This implemnents macros for utilizing "The Naive Extendible _Generic Macro" explained in: __| |
// https://github.com/JacksonAllan/CC/blob/main/articles/Better_C_Generics_Part_1_The_Extendible_Generic.md {___/
// Since gencpp is used to generate the c-library, it was choosen over the more novel implementations to keep the macros as easy to understand and unobfuscated as possible.
#define GEN_COMMA_OPERATOR , // The comma operator is used by preprocessor macros to delimit arguments, so we have to represent it via a macro to prevent parsing incorrectly.
// Helper macros for argument selection
#define GEN_SELECT_ARG_1( _1, ... ) _1 // <-- Of all th args passed pick _1.
#define GEN_SELECT_ARG_2( _1, _2, ... ) _2 // <-- Of all the args passed pick _2.
#define GEN_SELECT_ARG_3( _1, _2, _3, ... ) _3 // etc..
#define GEN_GENERIC_SEL_ENTRY_TYPE GEN_SELECT_ARG_1 // Use the arg expansion macro to select arg 1 which should have the type.
#define GEN_GENERIC_SEL_ENTRY_FUNCTION GEN_SELECT_ARG_2 // Use the arg expansion macro to select arg 2 which should have the function.
#define GEN_GENERIC_SEL_ENTRY_COMMA_DELIMITER GEN_SELECT_ARG_3 // Use the arg expansion macro to select arg 3 which should have the comma delimiter ','.
#define GEN_RESOLVED_FUNCTION_CALL // Just used to indicate where the call "occurs"
// ----------------------------------------------------------------------------------------------------------------------------------
// GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( macro ) includes a _Generic slot only if the specified macro is defined (as type, function_name).
// It takes advantage of the fact that if the macro is defined, then the expanded text will contain a comma.
// Expands to ',' if it can find (type): (function) <comma_operator: ',' >
// Where GEN_GENERIC_SEL_ENTRY_COMMA_DELIMITER is specifically looking for that <comma> ,
#define GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( slot_exp ) GEN_GENERIC_SEL_ENTRY_COMMA_DELIMITER( slot_exp, GEN_GENERIC_SEL_ENTRY_TYPE( slot_exp, ): GEN_GENERIC_SEL_ENTRY_FUNCTION( slot_exp, ) GEN_COMMA_OPERATOR, , )
// ^ Selects the comma ^ is the type ^ is the function ^ Insert a comma
// The slot won't exist if that comma is not found.
// For the occastion where an expression didn't resolve to a selection option the "default: <value>" will be set to:
typedef struct GENCPP_NO_RESOLVED_GENERIC_SELECTION GENCPP_NO_RESOLVED_GENERIC_SELECTION;
struct GENCPP_NO_RESOLVED_GENERIC_SELECTION {
void* _THE_VOID_SLOT_;
};
GENCPP_NO_RESOLVED_GENERIC_SELECTION const gen_generic_selection_fail = {0};
// Which will provide the message: error: called object type 'struct NO_RESOLVED_GENERIC_SELECTION' is not a function or function pointer
// ----------------------------------------------------------------------------------------------------------------------------------
// Below are generated on demand for an overlaod depdendent on a type:
// ----------------------------------------------------------------------------------------------------------------------------------
#define GEN_FUNCTION_GENERIC_EXAMPLE( selector_arg ) _Generic( \
(selector_arg), /* Select Via Expression*/ \
/* Extendibility slots: */ \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_1__function_sig ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_2__function_sig ) \
default: gen_generic_selection_fail \
) GEN_RESOLVED_FUNCTION_CALL( selector_arg )
// ----------------------------------------------------------------------------------------------------------------------------------
// Then each definiton of a function has an associated define:
#// #define GENERIC_SLOT_<#>_<generic identifier> <typename>, <function_to_resolve>
// Then somehwere later on
// <etc> <return_type> <function_id> ( <arguments> ) { <implementation> }
// Concrete example:
// To add support for long:
#define GENERIC_SLOT_1_gen_example_hash long, gen_example_hash__P_long
size_t gen_example_hash__P_long( long val ) { return val * 2654435761ull; }
// To add support for long long:
#define GENERIC_SLOT_2_gen_example_hash long long, gen_example_hash__P_long_long
size_t gen_example_hash__P_long_long( long long val ) { return val * 2654435761ull; }
// If using an Editor with support for syntax hightlighting macros:
// GENERIC_SLOT_1_gen_example_hash and GENERIC_SLOT_2_gen_example_hash should show color highlighting indicating the slot is enabled,
// or, "defined" for usage during the compilation pass that handles the _Generic instrinsic.
#define gen_hash_example( function_arguments ) _Generic( \
(function_arguments), /* Select Via Expression*/ \
/* Extendibility slots: */ \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_1_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_2_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_3_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_4_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_5_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_6_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_7_gen_example_hash ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_8_gen_example_hash ) \
default: gen_generic_selection_fail \
) GEN_RESOLVED_FUNCTION_CALL( function_arguments )
// Additional Variations:
// If the function takes more than one argument the following is used:
#define GEN_FUNCTION_GENERIC_EXAMPLE_VARADIC( selector_arg, ... ) _Generic( \
(selector_arg), \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_1__function_sig ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_2__function_sig ) \
/* ... */ \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT(GENERIC_SLOT_N__function_sig ) \
default: gen_generic_selection_fail \
) GEN_RESOLVED_FUNCTION_CALL( selector_arg, __VA_ARG__ )
// If the function does not take the arugment as a parameter:
#define GEN_FUNCTION_GENERIC_EXAMPLE_DIRECT_TYPE( selector_arg ) _Generic( \
( GEN_TYPE_TO_EXP(selector_arg) ), \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_1__function_sig ) \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT( GENERIC_SLOT_2__function_sig ) \
/* ... */ \
GEN_IF_MACRO_DEFINED_INCLUDE_THIS_SLOT(GENERIC_SLOT_N__function_sig ) \
default: gen_generic_selection_fail \
) GEN_RESOLVED_FUNCTION_CALL()
// Used to keep the _Generic keyword happy as bare types are not considered "expressions"
#define GEN_TYPE_TO_EXP(type) (* (type*)NULL)
// Instead of using this macro, you'll see it directly expanded by the code generation.
// typedef void* GEN_GenericExampleType;
// GEN_FUNCTION_GENERIC_EXAMPLE_DIRECT_TYPE( GEN_GenericExampleType );
#pragma endregion _Generic Macros