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{{TOC|side|0.9}}
The PreProcessor and the Config Parser allow to use macros in configs. The purpose of macros is to re-use the same definition in scripts and configs multiple times. It also gives a centralized place to correct errors in this definition.
Know that edge cases may arise - see the collection of test-cases linked at the end of this page.
{{Feature | arma3 | In {{arma3}}, preprocessor commands are '''case-sensitive!'''}}


== Parsing ==

See {{HashLink|#Config Parser}} below:
* '''[[Config.cpp]]''' - parsed when PBO is binarized.
** [[localize]] cannot be used in macros, as it would hardcode string of current language instead of creating reference.
* '''[[Description.ext]]''' - parsed when mission is loaded or previewed in missions list.
* '''[[SQF Syntax|SQF]] script''' - parsed when [[preprocessFile]], [[preprocessFileLineNumbers]], [[compileScript]] or [[execVM]] is used.

== Macros ==

=== Comments ===

A comment is a line within code that is not actually processed by the game engine. They are used to make code more readable or to add notes for future reference. The preprocessor removes all comments from the file before it is processed. Therefore, comments are never actually "seen" by the game engine.

 {{cc|this is a single-line comment}}
 
 {{codecomment|/*
 	this is a
 	multi-line
 	comment
 */}}
 
 myValue = something; {{cc|only this part of the line is commented out}}
 
 myArray = ["apple"{{codecomment|/*,"banana*/}},"pear"]; {{cc|a portion in the middle of this line is commented out}}

=== #define ===

Using the ''#define'' instruction, it is possible to define a keyword and assign a definition to it. The keyword may contain any letter, digit or underscore in arbitrary order, as long as it does not start with a digit (RegEx: <tt>[a-zA-Z_][0-9a-zA-Z_]*</tt>). As an example:
<syntaxhighlight lang="cpp">
#define true 1
</syntaxhighlight>

The above means that whenever ''true'' is used in a config, the parser will replace this with the value ''1''.

The define-statement does swallow all spaces in between the macro-keyword and any non-space-character in the body (Note that tabs are not spaces! They don't get removed)
<syntaxhighlight lang="cpp">
#define MACRO                     test
MACRO // preprocesses to test (without any spaces)

#define MACRO	test // There's a tab between MACRO and test
MACRO // preprocesses to "	test" (without quotes - they are only used to show that the tab character didn't get removed)
</syntaxhighlight>

The space between the macro-keyword and the body is also fully optional (though very useful to tell the preprocessor where the macro name ends and where the body begins):
<syntaxhighlight lang="cpp">
#define MACRO#test
MACRO // preprocesses to "test"
</syntaxhighlight>

==== Arguments ====
Arguments can be added to more complex macros, by including them between brackets after the keyword. For the name of the arguments the same rule as for the macro-keyword (see above) apply.
<syntaxhighlight lang="cpp">
#define CAR(NAME) displayName = NAME;
</syntaxhighlight>

If ''CAR("Mini")'' is used, it will be replaced with ''displayName = "Mini";''. Multiple arguments can also be used:
<syntaxhighlight lang="cpp">
#define BLASTOFF(UNIT,RATE) UNIT setVelocity [0,0,RATE];
</syntaxhighlight>

Macro arguments may be composed of any characters, as long as they do not contain a comma (because commas are used as argument-delimiters). If quotes are being used, they have to be balanced. The same applies to single-quotes This is because String detection is working in macro arguments - Therefore commas can even get passed in as a macro argument as long as they are part of a String (This only works with Strings wrapped in double-quotes though). Note however that although the macro gets resolved properly, the comma gets removed from the String (probably a bug).
<syntaxhighlight lang="cpp">
#define MACRO(arg) arg
MACRO("Some, content") // preprocesses to "Some content" (note the missing comma)
</syntaxhighlight>

Quote escaping is also not supported in this context (neither with double- nor with single-quotes)
<syntaxhighlight lang="cpp">
#define MACRO(arg) arg
MACRO("Some ""content""") // preprocesses to "Some ""content"""
</syntaxhighlight>

Passing arrays with more than one element <tt>[el1,el2,...]</tt> as arguments into macros as well as any argument containing comas <tt>"some, sentence"</tt>, will need a small workaround:
<syntaxhighlight lang="cpp">
#define HINTARG(ARG) hint ("Passed argument: " + str ARG)
</syntaxhighlight>

Incorrect usage:
<syntaxhighlight lang="cpp">
HINTARG([1,2,3,4,5,6,7,8,9,0]); // ERROR, won't even compile
</syntaxhighlight>

Correct usage:
<syntaxhighlight lang="cpp">
#define array1 [1,2,3,4,5,6,7,8,9,0] 
HINTARG(array1); // SUCCESS
</syntaxhighlight>

The argument replacement is performed before the expansion of the macro body. That means one doesn't have to worry about name-conflicts between argument-names of the current macro and already defined macros:
<syntaxhighlight lang="cpp">
#define ONE foo
#define TWO(ONE) ONE
TWO(bar) // will preprocess to bar
</syntaxhighlight>

==== Replacing parts of words ====
By default, only whole words can be replaced by arguments. If only a part of the word should be replaced, use the ''##'' instruction. This is necessary when either the start or the end of the argument connects to another character that is not a ''';''' (semi-colon) or &nbsp; (space).
<syntaxhighlight lang="cpp">
class NAME##_Button_Slider: RscText \
{ \
	model = \OFP2\Structures\Various\##FOLDER##\##FOLDER; \
</syntaxhighlight>

It is also possible to use the single ''#'' to convert an argument to a string.
<syntaxhighlight lang="cpp">
statement = (this animate [#SEL, 0]); \
</syntaxhighlight>

==== Multi-line ====
For longer definitions, one can stretch the macro across multiple lines. To create a multi-line definition, each line except the last one should end with a ''\'' character:
<syntaxhighlight lang="cpp">
#define DRAWBUTTON(NAME)\
	__EXEC(idcNav = idcNav + 4) \
	...
</syntaxhighlight>

{{Feature | Informative | The backslash must be the last character in a line when defining a multi-line macro. Any character (including spaces) after the backslash will cause issues.}}

=== #undef ===

Undefine (delete) a macro previously set by the use of #define.
<syntaxhighlight lang="cpp">
#undef NAME
</syntaxhighlight>

=== #if  ===

'''Description:''' Checks condition and processes content if condition returns 1. Skips content if it returns 0
<syntaxhighlight lang="cpp">
#if __A3_DEBUG__ // Check if game is started in debug mode
#include "debug.hpp" // Include some file if debug mode is enabled
#endif
</syntaxhighlight>

=== #ifdef ===

A simple if-then construction to check whether a certain set of definitions has already been made:
<syntaxhighlight lang="cpp">
#ifdef NAME
	...text that will be used if NAME is defined...
#endif
</syntaxhighlight>

IFDEFs ''cannot'' be nested. The preprocessor will generate errors for all inner definitions if the outer definition doesn't exist.

=== #ifndef ===

Same as #ifdef, but checks for absence of definition instead.
<syntaxhighlight lang="cpp">
#ifndef NAME
	...text that will be used if NAME ''isn't'' defined...
#endif
</syntaxhighlight>

=== #else ===

Provides alternative code to <tt>#if</tt>, <tt>#ifdef</tt>, <tt>#ifndef</tt> checks.
<syntaxhighlight lang="cpp">
#ifndef NAME
	...text that will be used if NAME is -not- defined...
#else
	...text that will be used if NAME -is- defined...
#endif
</syntaxhighlight>

=== #endif ===

This ends a conditional block as shown in the descriptions of #ifdef and #ifndef above.

=== #include ===

Copies the code from a target file and pastes it where #include directive is.
<syntaxhighlight lang="cpp">
#include "file.hpp"
#include <file.txt> // Brackets are equivalent to quotation marks and may be used in their place.
</syntaxhighlight>

Source directory is:
* For any file without starting the include path with \ - the file's current directory
* When starting with \ - the internal filesystem root (see [[CMA:DevelopmentSetup#Addon_development|Addon Development]]) or the Game's working directory (only with [[Arma 3 Startup Parameters|-filePatching]] enabled)

A path beginning can be defined as follow:
* drive (only with [[Arma 3 Startup Parameters|-filePatching]] enabled): <syntaxhighlight lang="cpp">#include "D:\file.txt"</syntaxhighlight>
* PBO with [[PBOPREFIX]]: <syntaxhighlight lang="cpp"> #include "\myMod\myAddon\file.txt"</syntaxhighlight>
* PBO (keep in mind that in this case, if the PBO's file name will be changed, all '#include' referencing it will need to be updated):<!--
--><syntaxhighlight lang="cpp">#include"\myMod\myAddon\file.txt" // Arma 3\@myMod\addons\myAddon.pbo\file.txt;</syntaxhighlight>

To move to parent directory use '..' (two dots) (Supported since {{GVI|arma3|1.50}}):
<syntaxhighlight lang="cpp">
#include "..\file.sqf"
</syntaxhighlight>

Preprocessor does not support the use of macros for pre-defined file names.
<syntaxhighlight lang="cpp">
#define path "codestrip.txt"
#include path // this will cause an error
</syntaxhighlight>

=== # ===

'#' (single hash) operator wraps the text with quotation marks.
<syntaxhighlight lang="cpp">
#define STRINGIFY(s) #s;
#define FOO 123
test1 = STRINGIFY(123); //test1 = "123";
test2 = STRINGIFY(FOO); //test2 = "123";
</syntaxhighlight>

This operator does only work on keywords following the rules for macro-names (see <tt>#define</tt>-section). If one wants to stringify anything else (like e.g. a number), one has to use a stringify-macro that takes an argument and stringifies that (as in the example above).
<syntaxhighlight lang="cpp">
#define MACRO Test #123
MACRO // preprocesses to Test 123 - note that there are not any quotes inserted
</syntaxhighlight>

=== ## ===

'##' (double hash) operator concatenates what's before the ## with what's after it.
<syntaxhighlight lang="cpp">
#define GLUE(g1,g2) g1##g2
#define FOO 123
#define BAR 456
test1 = GLUE(123,456); //test1 = 123456;
test2 = GLUE(FOO,BAR); //test2 = 123456;
</syntaxhighlight>

=== __LINE__ ===

This keyword gets replaced with the line number in the file where it is found. For example, if __LINE__ is found on the 10th line of a file, the word __LINE__ will be replaced with the number 10.

=== __FILE__ ===

This keyword gets replaced with the CURRENT file being processed.

{{ArgTitle|3|__has_include|{{GVI|arma3|2.02}}}}

'''Description:''' Checks if given file exists. Returns 1 if it does, 0 if it does not exist.
 #if __has_include("\z\ace\addons\main\script_component.hpp")
 {{cc|File exists! Do something with it}}
 #else
 {{cc|File does not exist}}
 #endif

{{ArgTitle|3|__DATE_ARR__|{{GVI|arma3|2.02}}}}

'''Description:''' Is replaced for current date in format [[Array|array]].
 __DATE_ARR__ {{cc|2020,10,28,15,17,42}}

{{ArgTitle|3|__DATE_STR__|{{GVI|arma3|2.02}}}}

'''Description:''' Is replaced for current date in format [[String|string]].
 __DATE_STR__  {{cc|"2020/10/28, 15:17:42"}}

{{ArgTitle|3|__DATE_STR_ISO8601__|{{GVI|arma3|2.02}}}}

'''Description:''' Is replaced for current date in format [[String|string]]. The date is presented in ISO8601 standard.
 __DATE_STR_ISO8601__ {{cc|"2020-10-28T14:17:42Z"}}

{{ArgTitle|3|__TIME__|{{GVI|arma3|2.02}}}}

'''Description:''' Is replaced for current time.
 __TIME__ {{cc|15:17:42}}

{{ArgTitle|3|__TIME_UTC__|{{GVI|arma3|2.02}}}}

'''Description:''' Is replaced for  UTC time.
 __TIME_UTC__ {{cc|14:17:42}}

{{ArgTitle|3|__COUNTER__|{{GVI|arma3|2.02}}}}

'''Description:''' Counts 1 up everytime it is defined.
 __COUNTER__ {{cc|0}}
 __COUNTER__ {{cc|1}}
 __COUNTER__ {{cc|2}}
 __COUNTER__ {{cc|3}}
 __COUNTER_RESET__
 __COUNTER__ {{cc|0}}
 __COUNTER__ {{cc|1}}
 __COUNTER__ {{cc|2}}

{{ArgTitle|3|__COUNTER_RESET__|{{GVI|arma3|2.02}}}}

'''Description:''' Resets counter. See example above.

{{ArgTitle|3|__RAND_INT<tt>N</tt>__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by a random <tt>N</tt> bit integer. <tt>N</tt> can be 8, 16, 32 or 64, e.g:
<syntaxhighlight lang="cpp">
__RAND_INT8__
__RAND_INT16__
__RAND_INT32__
__RAND_INT64__
</syntaxhighlight>

 __RAND_INT8__ {{cc|e.g -102}}

{{ArgTitle|3|__RAND_UINT<tt>N</tt>__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by a random ''unsigned'' <tt>N</tt> bit integer. <tt>N</tt> can be 8, 16, 32 or 64, e.g:
<syntaxhighlight lang="cpp">
__RAND_UINT8__
__RAND_UINT16__
__RAND_UINT32__
__RAND_UINT64__
</syntaxhighlight>

 __RAND_UINT8__ {{cc|108}}

{{ArgTitle|3|__GAME_VER__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by the game version.
 __GAME_VER__ {{cc|02.00.146790}}

{{ArgTitle|3|__GAME_VER_MAJ__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by the ''major'' game version. 
 __GAME_VER_MAJ__ {{cc|02}}

{{ArgTitle|3|__GAME_VER_MIN__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by the ''minor'' game version.
 __GAME_VER_MIN__ {{cc|00}}

{{ArgTitle|3|__GAME_BUILD__|{{GVI|arma3|2.02}}}}

'''Description:''' Gets replaced by the build number.
 __GAME_BUILD__ {{cc|146790}}

{{ArgTitle|3|__ARMA__|{{GVI|arma3|2.02}}}}

'''Description:''' {{Wiki|stub}}
 __ARMA__ {{cc|1}}

{{ArgTitle|3|__ARMA3__|{{GVI|arma3|2.02}}}}

'''Description:''' {{Wiki|stub}}
 __ARMA3__ {{cc|1}}

{{ArgTitle|3|__A3_DEBUG__|{{GVI|arma3|2.02}}}}

'''Description:''' This macro is only set when the [[Arma 3 Startup Parameters| -debug parameter]] was provided. It can be used to switch mods or scripts to debug mode dynamically.
 __A3_DEBUG__ {{cc|1 (If -debug was enabled)}}


== Config Parser ==

{{Feature|important|'''Config Parser''' keywords '''cannot''' be used in preprocessor {{HashLink|#Macros}}, e.g '''{{HashLink|##if}}'''!}}

=== __EXEC ===

This '''Config Parser''' macro allows to assign values to internal variables or just execute arbitrary code. The code inside <tt>__EXEC</tt> macros runs in [[parsingNamespace]] and variables defined in it will also be created in [[parsingNamespace]]. The variables can then be used to create more complex macros:

 __EXEC(cat = 5 + 1;)
 __EXEC(lev = cat - 2;)
 _cat = [[parsingNamespace]] [[getVariable]] "cat"; {{cc|6}}
 _lev = [[parsingNamespace]] [[getVariable]] "lev"; {{cc|4}}

{{Feature | Warning |
<tt>__EXEC</tt> doesn't like round brackets <tt>()</tt> inside expressions. If grouping is needed, perhaps values could be calculated inside the brackets separately and assigned to local variables:
<code>__EXEC(a {{=}} (1+2);) {{cc|ERROR}}</code>
<div><code>__EXEC(_expr {{=}} 1+2;)
__EXEC(a {{=}} _expr;) {{cc|OK}}</code></div>
}}

=== __EVAL ===

With this '''Config Parser''' macro expressions can be evaluated, including previously assigned internal variables. Unlike <tt>__EXEC</tt>, <tt>__EVAL</tt> supports multiple parentheses:

 w = __EVAL([[safeZoneW]] - (5 * ((1 / ([[getResolution]] [[select]] 2)) * 1.25 * 4)));

<tt>__EVAL</tt> macros '''must''' be assigned to a config property and the expression '''must''' be terminated with <tt>;</tt>. <tt>__EVAL</tt> can only return [[Number]] or [[String]]: . Any other type is represented as [[String]], even [[Boolean]] type, which will result in either <tt>"true"</tt> or <tt>"false"</tt>.

{{Feature | Warning |
<tt>__EVAL</tt> doesn't like curly brackets <tt>{}</tt>; if code is needed in the expression, use [[compile]] [[String]] instead:
<code>result {{=}} __EVAL([[call]] {123}); {{cc|ERROR}}</code>
<code>result {{=}} __EVAL([[call]] [[compile]] "123"); {{cc|OK}}</code>}}

{{Feature|important|<tt>__EXEC</tt> and <tt>__EVAL</tt> macros are not suitable for SQF/SQS scripts but can be used in configs, including [[Description.ext|description.ext]]. <br>Both global and local variables set in <tt>__EXEC</tt> are available in <tt>__EVAL</tt>}}


== Errors ==

=== Error 2 ===

; Problem: Preprocessor failed error 2.

; How to fix: Add quotation marks in the title, or the file path. (''e.g.'' <tt>#include "soGood.sqf"</tt>).

=== Error 6 ===

; Problem: Preprocessor failed on file X - error 6.

; Known reasons:
: "The problem is using <tt>#ifdef #ifdef #endif #endif</tt>, a.k.a nested <tt>#ifdef</tt>. This doesn't work in Arma. It's only possible to use <tt>#ifdef</tt> and <tt>#endif</tt> once and not nested."
: <tt>#endif</tt> without preceding <tt>#ifdef</tt> or <tt>#ifndef</tt>

=== Error 7 ===

; Problem: Preprocessor failed on file X - error 7.

; Known reasons: The preprocessor encountered an unknown directive. Read, as a typo most has likely found a way into the file (something like <tt>#inlcude</tt> or <tt>#defien</tt>). Double-check all preprocessor directives in that file.


== External links ==

* [https://web.archive.org/web/20170319190732/http://ofp-faguss.com/files/ofp_preprocessor_explained.pdf {{ofp}} - Preprocessor Guide (Wayback Machine)]
* [https://github.com/Krzmbrzl/ArmaPreprocessorTestCases Collection of preprocessor test-cases]

[[Category:Scripting_Topics]]