X macros - Revision history

Vegard: add category

2020-03-01T11:54:29Z

add category

← Older revision		Revision as of 11:54, 1 March 2020
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	[[Category:Programming]]		[[Category:Programming]]
	[[Category:C++]]		[[Category:C++]]
			[[Category:C preprocessor snippets]]

Vegard: /* See also */ add link

2020-02-29T07:57:44Z

Vegard: Vegard moved page The X macro to X macros

2019-12-19T09:00:04Z

Vegard moved page The X macro to X macros

← Older revision		Revision as of 09:00, 19 December 2019
(No difference)

Vegard: /* Serialization */

2019-12-19T08:59:41Z

Serialization

← Older revision		Revision as of 08:59, 19 December 2019
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	== Serialization ==		== Serialization ==

	You can use the same technique to define structs and also generate code to serialize them:		You can use the same technique to define structs and also generate code to inspect them (reflection) or serialize them:

	<source lang="C++">		<source lang="C++">

Vegard: serialisation

2019-12-15T06:46:35Z

serialisation

@@ Line 1: / Line 1: @@
 Definitions:
@@ Line 88: / Line 92: @@
 => ADD
 => SUB
 </pre>

Vegard: /* See also */ correct order

2019-12-14T19:08:58Z

Vegard: new page

2019-12-14T19:00:11Z

new page

New page

Definitions:

<source lang="C++">
#define _DEFINE_ENUM_NAME(name) name,
#define _DEFINE_ENUM_STR(name) #name,
#define DEFINE_ENUM(name) \
enum name { \
name(_DEFINE_ENUM_NAME) \
}; \
\
const char *name##_names[] = { \
name(_DEFINE_ENUM_STR) \
}; \
\
const unsigned int nr_##name##s = sizeof(name##_names) / sizeof(*name##_names);
</source>

Usage:

<source lang="C++">
#define opcode(X) \
X(LOAD_CONSTANT) \
X(LOAD_LOCAL) \
X(STORE_LOCAL) \
X(ADD) \
X(SUB)

DEFINE_ENUM(opcode)
</source>

This defines <tt>enum opcode</tt> which contains <tt>LOAD_CONSTANT</tt>, etc.
You can also map enum values to strings using the <tt>opcode_names</tt> array, like this:

<source lang="C++">
void print_value(enum opcode opc)
{
printf("%s\n", opcode_names[opc]);
}
</source>

=== Discontiguous values ===

For bitfields and cases where you need specific values, you can also modify the definition to allow specific/discontiguous enum values.

To avoid the name array from growing too large it is probably useful to use a map instead of an array.

<source lang="C++">
#include <map>

#define _DEFINE_ENUM_NAME(name) name,
#define _DEFINE_ENUM_NAME_VALUE(name, value) name = value,

#define _DEFINE_ENUM_VALUE_STR1(name) { name, #name },
#define _DEFINE_ENUM_VALUE_STR2(name, value) { name, #name },

#define DEFINE_ENUM(name) \
enum name { \
name(_DEFINE_ENUM_NAME, _DEFINE_ENUM_NAME_VALUE) \
}; \
\
std::map<enum name, const char *> name##s = { \
name(_DEFINE_ENUM_VALUE_STR1, _DEFINE_ENUM_VALUE_STR2) \
};

#define opcode(X, Y) \
Y(LOAD_CONSTANT, 100) \
X(LOAD_LOCAL) \
Y(STORE_LOCAL, 200) \
Y(ADD, 300) \
X(SUB)

DEFINE_ENUM(opcode)

int main(int argc, char *argv[])
{
for (auto &it: opcodes)
printf("%d => %s\n", it.first, it.second);

return 0;
}
</source>

This prints:
<pre>
100 => LOAD_CONSTANT
101 => LOAD_LOCAL
200 => STORE_LOCAL
300 => ADD
301 => SUB
</pre>

== See also ==
* https://en.wikipedia.org/wiki/X_Macro
* https://philliptrudeau.com/blog/x-macro

[[Category:Programming]]
[[Category:C++]]

← Older revision		Revision as of 07:57, 29 February 2020
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	* https://philliptrudeau.com/blog/x-macro		* https://philliptrudeau.com/blog/x-macro
	* https://en.wikipedia.org/wiki/X_Macro		* https://en.wikipedia.org/wiki/X_Macro
			* https://stackoverflow.com/questions/8662395/counting-preprocessor-macros

	[[Category:Programming]]		[[Category:Programming]]

← Older revision		Revision as of 19:08, 14 December 2019
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	== See also ==		== See also ==
⚫	* https://en.wikipedia.org/wiki/X_Macro
	* https://philliptrudeau.com/blog/x-macro		* https://philliptrudeau.com/blog/x-macro
		⚫	* https://en.wikipedia.org/wiki/X_Macro

	[[Category:Programming]]		[[Category:Programming]]