as: a syntax question.

stf92 · 07-10-2011, 05:00 PM

as 2.17

Hi:
I want to code this:

and byte[45],03

In words, AND the byte at memory location 45 with immediate value 03.
as reports "Ambiguous operand size for and". How could I code the instruction such that as understands my intention?

john: .byte 45
and byte[john],03

gives the same error.

Sergei Steshenko · 07-10-2011, 05:06 PM

Quote:

Originally Posted by stf92

as 2.17

Hi:
I want to code this:

and byte[45],03

In words, AND the byte at memory location 45 with immediate value 03.
as reports "Ambiguous operand size for and". How could I code the instruction such that as understands my intention?

john: .byte 45
and byte[john],03

gives the same error.

You probably have to declare '03' as byte too.

dogpatch · 07-10-2011, 10:30 PM

I am not familiar with as, but in gcc assembly, the op code must in many cases specify the size, as in

Code:

 andb $3,$John

the 'b' in 'andb' designating 'byte'.

This thread has me wondering how i missed as. I went through alot of work converting many of my old Dos masm source files to gcc assembly. Wrote a C program to do most of the converting.

stf92 · 07-11-2011, 02:55 AM

Thanks. andb turned up to be correct. I had the .intel_syntax directive in the source, but it surely is the same in AT&T syntax.

I am also in the task of converting a MASM source file to some linux assembler.

dogpatch · 07-11-2011, 09:15 AM

Quote:

Originally Posted by stf92

I am also in the task of converting a MASM source file to some linux assembler.

If you have lots of code to convert, it may be worth the effort to write a C program to convert the code line by line. I don't think a shell script would answer in this case, since there are too many factors in just a single line. e.g. transposing the operands, adding byte or word indicators, converting comments, etc.

Anyway, that's how i skinned this particular cat. Still had some tinkering to do afterwards by hand, but in the end saved me lots of time.

Sergei Steshenko · 07-11-2011, 11:17 AM

Quote:

Originally Posted by dogpatch

...it may be worth the effort to write a C program to convert the code line by line. ...

Rather a Perl program. And probably a lot of conversions can be made writing specialized macros in the the assembly itself.

stf92 · 07-11-2011, 11:39 AM

@dogpatch: the program would have to do much less work if you feed the output to nasm instead of as. Nasm is almost compatible with MASM. Also, in as, you can turn intel syntax on with the .intel_syntax directive.

dogpatch · 07-11-2011, 04:14 PM

In any case, whether Perl or C, nasm or as: a batch program to do most of the conversion seems like a good investment of time.

stf92 · 07-11-2011, 05:42 PM

Indeed!