Use #define or EQU in assembler

[satyria]

Hello,
I want to make my assembler code more readable and wanted to use something like #define (EQU).
I use "Gnu-AS".
Example:

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#define BASE 0xFE000000
   ...
   ...
ldr r0,= BASE
   ...
   ...

Unfortunately, the linker shows an error when compiling:

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build/main.o: in function `wait2$':
(.init+0x8044): undefined reference to `BASE'

By the way: BASE is not used in the WAIT function.
What options are there with the Gnu-AS?

Greetings, Matthias

[trejan]

The equivalent to #define in gas is .set

You need to feed it through the cpp preprocessor first if you want to use #define. Either add that as part of your build script or give your source file the .S extension and use gcc on it.

[dwelch67]

#define is C and not assembly language (gnu assembler), so you would want to use equ. Otherwise it is yet another assembly/hybrid language and you have to pass it through the C preprocessor before it goes to the assembler.

[satyria]

many thanks

Unfortunately, equ did not work either. same error.

I've just read the GAS documentary. The attempt with "=" worked within the code:

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BASE = 0xFE200000

However, when I try to load this with .include, the same error occurs again.
in the "main.s" file:

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.include ../include/base.h
...
...

The base.h:

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BASE = 0xFE200000

[satyria]

Sorry, found my mistake. It works as described.
However, I have a new question: I would now like to set a value that I would like to process via .if query. Example:

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...
.equ RPI_Version, "1a"
...
...
.if RPI_Version == "1a" 
   ....
 .endif
 

However, this does not work because the assembler does not understand the "a" under .equ here. How can I avoid that?
How can I use strings for .if?
Greetings, Matthias

[LdB]

Use just numbers

The `#if' directive allows you to test the value of an arithmetic expression, rather than the mere existence of one macro. Its syntax is
#if expression
controlled text
#endif

#ifdef in C is for strings but I don't think the assembler can handle them but admittedly I would never do it so check you might get lucky.

[satyria]

I found a solution.
Example:

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...
.equ RPI_Version_1a, 1
...
...
.ifdef RPI_Version_1a
	...
.endif 

Greetings Matthias