PreProcessor Commands

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.

In Arma 3, preprocessor commands are case-sensitive!

Parsing

• 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 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.

// this is a single-line comment
 
/*
	this is a
	multi-line
	comment
*/
 
myValue = something; // only this part of the line is commented out

myArray = { "apple"/*, "banana"*/, "pear" }; // 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: [a-zA-Z_][0-9a-zA-Z_]*). As an example:

#define true 1

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)

#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)

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):

#define MACRO#test
MACRO // preprocesses to "test"

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.

#define CAR(NAME) displayName = NAME;

If CAR("Mini") is used, it will be replaced with displayName = "Mini";. Multiple arguments can also be used:

#define BLASTOFF(UNIT,RATE) UNIT setVelocity [0,0,RATE];

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).

#define MACRO(arg) arg
MACRO("Some, content") // preprocesses to "Some content" (note the missing comma)

Quote escaping is also not supported in this context (neither with double- nor with single-quotes)

#define MACRO(arg) arg
MACRO("Some ""content""") // preprocesses to "Some ""content"""

Passing arrays with more than one element [el1,el2,...] as arguments into macros as well as any argument containing comas "some, sentence", will need a small workaround:

#define HINTARG(ARG) hint ("Passed argument: " + str ARG)

Incorrect usage:

HINTARG([1,2,3,4,5,6,7,8,9,0]); // ERROR, won't even compile

Correct usage:

#define array1 [1,2,3,4,5,6,7,8,9,0] 
HINTARG(array1); // SUCCESS

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:

#define ONE foo
#define TWO(ONE) ONE
TWO(bar) // will preprocess to bar

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   (space).

class NAME##_Button_Slider: RscText \
{ \
	model = \OFP2\Structures\Various\##FOLDER##\##FOLDER; \

It is also possible to use the single # to convert an argument to a string.

statement = (this animate [#SEL, 0]); \

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:

#define DRAWBUTTON(NAME)\
	__EXEC(idcNav = idcNav + 4) \
	// ...

ⓘ

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.

#undef NAME

#if

Description: Checks condition and processes content if condition returns 1. Skips content if it returns 0

#if __A3_DEBUG__ // Check if game is started in debug mode
#include "debug.hpp" // Include some file if debug mode is enabled
#endif

#ifdef

A simple if-then construction to check whether a certain set of definitions has already been made:

#ifdef NAME
	// config that will be used if NAME is defined
#endif

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.

#ifndef NAME
	// config that will be used if NAME is -not- defined
#endif

#else

Provides alternative code to #if, #ifdef, #ifndef checks.

#ifndef NAME
	// config that will be used if NAME is -not- defined
#else
	// config that will be used if NAME -is- defined
#endif

#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.

#include "file.hpp"
#include <file.txt> // Brackets are equivalent to quotation marks and may be used in their place.

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 Addon Development) or the Game's working directory (only with -filePatching enabled)

A path beginning can be defined as follow:

• drive (only with -filePatching enabled):

  #include "D:\file.txt"
  

• PBO with PBOPREFIX:

   #include "\myMod\myAddon\file.txt"
  

• 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):

  #include"\myMod\myAddon\file.txt" // Arma 3\@myMod\addons\myAddon.pbo\file.txt;
  

To move to parent directory use '..' (two dots) (Supported since 1.50):

#include "..\file.sqf"

Preprocessor does not support the use of macros for pre-defined file names.

#define path "codestrip.txt"
#include path // this will cause an error

#

'#' (single hash) operator wraps the text with quotation marks.

#define STRINGIFY(s) #s
#define FOO 123
test1 = STRINGIFY(123); //test1 = "123";
test2 = STRINGIFY(FOO); //test2 = "123";

This operator does only work on keywords following the rules for macro-names (see #define-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).

#define MACRO Test #123
MACRO // preprocesses to Test 123 - note that there are not any quotes inserted

##

'##' (double hash) operator concatenates what's before the ## with what's after it.

#define GLUE(g1,g2) g1##g2
#define FOO 123
#define BAR 456
test1 = GLUE(123,456); //test1 = 123456;
test2 = GLUE(FOO,BAR); //test2 = 123456;

__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.

2.02

__has_include

Description: Checks if given file exists. Returns 1 if it does, 0 if it does not exist.

⚠

• The file path must start with the backslash \ otherwise it would fail silently (returns 0 so does nothing unless you put something in #else)!
• If you wanted to make an addon that can change its config dynamically depending on mods that loaded along, do not binarize the config.cpp!

ⓘ

To validate that the file exists in your game, you can use fileExists command to check.

fileExists "\a3\data_f\config.bin"; // returns true fileExists "\z\ace\addons\main\script_component.hpp"; // returns true if ACE is loaded, false otherwise

#if __has_include("\z\ace\addons\main\script_component.hpp")
// file exists! Do something with it
#else
// file does not exist
#endif

2.02

__DATE_ARR__

Description: Is replaced for current date in format array.

__DATE_ARR__ // 2020,10,28,15,17,42

2.02

__DATE_STR__

Description: Is replaced for current date in format string.

__DATE_STR__  // "2020/10/28, 15:17:42"

2.02

__DATE_STR_ISO8601__

Description: Is replaced for current date in format string. The date is presented in ISO8601 standard.

__DATE_STR_ISO8601__ // "2020-10-28T14:17:42Z"

2.02

__TIME__

Description: Is replaced for current time.

__TIME__ // 15:17:42

2.02

__TIME_UTC__

Description: Is replaced for UTC time.

__TIME_UTC__ // 14:17:42

2.02

__COUNTER__

Description: Counts 1 up everytime it is defined.

__COUNTER__ // 0
__COUNTER__ // 1
__COUNTER__ // 2
__COUNTER__ // 3
__COUNTER_RESET__
__COUNTER__ // 0
__COUNTER__ // 1
__COUNTER__ // 2

2.06

__TIMESTAMP_UTC__

Description: Is replaced to the current timestamp in UNIX timestamp.

__TIMESTAMP_UTC__ // 1622639059

2.02

__COUNTER_RESET__

Description: Resets counter. See example above.

2.02

__RAND_INTN__

Description: Gets replaced by a random N bit integer. N can be 8, 16, 32 or 64, e.g:

__RAND_INT8__
__RAND_INT16__
__RAND_INT32__
__RAND_INT64__

__RAND_INT8__ // e.g -102

2.02

__RAND_UINTN__

Description: Gets replaced by a random unsigned N bit integer. N can be 8, 16, 32 or 64, e.g:

__RAND_UINT8__
__RAND_UINT16__
__RAND_UINT32__
__RAND_UINT64__

__RAND_UINT8__ // 108

2.02

__GAME_VER__

Description: Gets replaced by the game version.

__GAME_VER__ // 02.00.146790

2.02

__GAME_VER_MAJ__

Description: Gets replaced by the major game version.

__GAME_VER_MAJ__ // 02

2.02

__GAME_VER_MIN__

Description: Gets replaced by the minor game version.

__GAME_VER_MIN__ // 00

2.02

__GAME_BUILD__

Description: Gets replaced by the build number.

__GAME_BUILD__ // 146790

2.12

__A3_DIAG__

Description: Gets replaced by 1 on diag, undefined otherwise.

__GAME_BUILD__ // 1

2.02

__ARMA__

Description:

__ARMA__ // 1

2.02

__ARMA3__

Description:

__ARMA3__ // 1

2.02

__A3_DEBUG__

Description: This macro is only set when the -debug parameter was provided. It can be used to switch mods or scripts to debug mode dynamically.

__A3_DEBUG__ // 1 (If -debug was enabled)

__EXEC / __EVAL

Exec/Evals are used in paramfiles to create constant parameters from variables.

A paramfile is a config.cpp, a desc.ext, an rvmat etc.

Bi's naming them `paramfile`is an excellent choice to describe them. They can only store hard wired parameters. Not functions and not arithmetic expressions. (#defines CAN preprocess arithmetic to produce a constant.)

Being paramfiles, the Bis compiler does not handle C statements like the following

param1= 1; param2= param1+ 77; // the compiler cannot access param1

or

param1= myCfunc(); // sqf funcs yes, C funcs no

The way around this limitation is to use exec/eval SQF statements to produce constants

The only difference between an __EXEC and an __EVAL is that __EXEC sets internal variables, __EVAL sets eternal parameters. ANY sqf expressions that produce a constant can be used in either

__EXEC will set or reset an internal variable to a value

In it's simplest form:

__EXEC(fred= 77);

• the variable 'fred' is only known and shared by execs and evals

A complex eval would be:

__EXEC(fred=1; mary=2 * Cos 80); // note the semi required between statements

Neither __EXEC nor __EVAL can 'read' an existing parameter

__EVAL can set an outside param.

new_param=__EVAL(fred+99; fred=fred+1;);

• Note that #defines can be used in exec or eval
• note that these are pre processor commands. they don't exist in the binarised equivalent.
• note that sqf is inherent in the compiler thus

angle= Rad+90; // requires no exec/eval

common usage

the most common use by bis is incrementing hitpoints

#define DO_IT  hit= __EVAL(count); __EXEC(count=count+1)

__EXEC(count=1);
class one
{
     hit=DO_IT;
     ....
};
class two
{
     hit=DO_IT;
     ....
};
etc etc

Errors

Error 2

Problem

Preprocessor failed error 2.

How to fix

Add quotation marks in the title, or the file path. (e.g. #include "soGood.sqf").

Error 6

Problem

Preprocessor failed on file X - error 6.

Known reasons

"The problem is using #ifdef #ifdef #endif #endif, a.k.a nested #ifdef. This doesn't work in Arma. It's only possible to use #ifdef and #endif once and not nested."

#endif without preceding #ifdef or #ifndef

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 #inlcude or #defien). Double-check all preprocessor directives in that file.

External links

• Operation Flashpoint - Preprocessor Guide (Wayback Machine)
• Collection of preprocessor test-cases