CODEWITHSUNDEEP
assemblyarm
user1415536
user1415536

Reputation: 266

arm-none-eabi-as and ARM comments sign ';'

I have to ask it... It literally has driven me crazy for days already. After the choosing as toolchain an arm-none-eabi my life became a kind of nightmare and the reason is a very simple - arm-none-eabi-as treats every comment as an instruction and moreover sometimes it just doesn't understand an ARM assembler throwing fancy errors like "AREA is a bad instruction"...

Here is the code I copied and paste from the keil's docs:

AREA     Loadcon, CODE, READONLY
    ENTRY                              ; Mark first instruction to execute
start
    BL       func1                     ; Branch to first subroutine
    BL       func2                     ; Branch to second subroutine
stop
    MOV      r0, #0x18                 ; angel_SWIreason_ReportException
    LDR      r1, =0x20026              ; ADP_Stopped_ApplicationExit
    SVC      #0x123456                 ; ARM semihosting (formerly SWI)
func1
    LDR      r0, =42                   ; => MOV R0, #42
    LDR      r1, =0x55555555           ; => LDR R1, [PC, #offset to
                                       ; Literal Pool 1]
    LDR      r2, =0xFFFFFFFF           ; => MVN R2, #0
    BX       lr
    LTORG                              ; Literal Pool 1 contains
                                       ; literal Ox55555555
func2
    LDR      r3, =0x55555555           ; => LDR R3, [PC, #offset to
                                       ; Literal Pool 1]
    ; LDR r4, =0x66666666              ; If this is uncommented it
                                       ; fails, because Literal Pool 2
                                       ; is out of reach
    BX       lr
LargeTable
    SPACE    4200                      ; Starting at the current location,
                                       ; clears a 4200 byte area of memory
                                       ; to zero
    END                                ; Literal Pool 2 is empty

My question is: What flags should I use to make arm-none-eabi-as to understand its very own assembler instructions and treat comments as comments?

*ADDED: * Here is the command I'm using to compile this code:

arm-none-eabi-gcc hello.S -Os -g -mthumb -mcpu=cortex-m3 -msoft-float -o hello.elf

Upvotes: 1

Views: 4519

Answers (3)

auselen
auselen

Reputation: 28087

One should check gnu as's documentation. Generally every architecture has its own differences about syntax. ARM is no different.

Upvotes: 1

Michael
Michael

Reputation: 58427

The default character for starting a single-line comment in GNU's ARM assembly syntax is @ IIRC. As in:

BL   func1             @ Branch to first subroutine

As for the assembler directives; they are assembler-specific, so you can't just take armasm code and assemble it with GNU's assembler, or vice versa. You'll have to look up what each directive means and try to find a corresponding one for the assembler you're going to use.

For example, to replace AREA Loadcon, CODE, READONLY you could probably use .text (unless you need to be able to refer to the section by its name).

Upvotes: 5

old_timer
old_timer

Reputation: 71506

The gnu assembler is well known for making up its own assembly language to replace well established syntaxes. Basically your arm assembler syntax as written wont work with gnu. As far as comments go I prefer to use a combination of both ;@ for my comments, beyond that you will need to figure out syntax that is common between both, at one point when I was developing for both I would/could write code that assembled on both, but I dont have access any more.

yes this is very frustrating...

Upvotes: 1

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