Macro instructions in MASM and GAS

Although the core idea behind the macro instruction mechanism is the same across all assemblers, the syntax of macro instructions and the capabilities of the engine vary. The following are two examples of simple macros for MASM and GAS.

Microsoft Macro Assembler

Remember our test program for MASM in Chapter 2, Setting Up a Development Environment? We can replace the code that invokes the show_message procedure with the following macro instruction:

MSHOW_MESSAGE MACRO title, message ;macro_name MACRO parameters
   push message
   push title
   call show_message
ENDM

This may make the code a bit more readable as we may then call the show_message procedure this way:

MSHOW_MESSAGE offset ti, offset msg

The GNU Assembler

The macro engine of the GNU Assembler is quite similar to that of Microsoft's MASM, yet there are a few syntactic differences (not taking into account the overall syntax difference) that we have to pay attention to. Let us take the output_message procedure...