Breaking long macro argument list in GNU assembler for AArch64-CodePudding

I'm writing assembly code targeting ARMv8 (AArch64) in GNU assembler. Not sure if it matters, but I'm coding directly in my ARMv8 target (a Raspberry Pi board) running Linux.

I have a macro with a very long argument list (as in, over 60 arguments) -- I know, this is just wrong, please don't shoot me.

For readability, I'd like to break this argument list over multiple lines, i.e. something like this:

.macro my_macro arg1, arg2, arg3, arg4,
                arg5, arg6, arg7, arg8,
                // ...
                arg61, arg62, arg63, arg64

    // macro code goes here

.endm

I'd also like to do the same when instantiating the macro.

Unfortunately, as soon as I try to insert a line break in the macro declaration, I get the following error:

test.s: Assembler messages:
test.s:123: Error: Bad parameter list for macro `my_macro'

As for inserting a line break in the macro instantiation, although I don't directly receive an error, the code doesn't assemble because all parameters after the line break are ignored, i.e. as though I had instantiated the macro with fewer parameters than it expects, so the missing ones default to an empty string.

According to the manual:

The ‘;’ character can be used instead of a newline to separate statements.

I tried to add a ; to the end of each line, i.e.:

.macro my_macro arg1, arg2, arg3, arg4, ;
                arg5, arg6, arg7, arg8, ;
                // ...
                arg61, arg62, arg63, arg64

    // macro code goes here

.endm

This made no difference. Same thing for a line break in the macro instantiation. I also tried other characters, such as #, @ and // with no luck.

So: is it possible to insert line breaks in the middle of the argument list in a macro declaration or instantiation?

CodePudding user response：

I don't know a way to do this in the assembler itself. However, a common practice when writing Unix-style assembly is to run your source through the C preprocessor before passing it on to the assembler. It's common enough that the gcc command will do it for you if you give your source file a name ending in .S with an upper case S.

The C preprocessor does support backslash line continuation, so in that case you can write

.macro my_macro arg1, arg2, arg3, arg4,     \
                arg5, arg6, arg7, arg8,     \
                // ...
                arg61, arg62, arg63, arg64  

    // macro code goes here
.endm

and the whole .macro directive will be seen as a single line by the assembler.

Having the C preprocessor also gives you the ability to use C-style macros with #define, in case that is useful.