Gas altmacro macro with a percent sign in a default parameter fails with “% operator needs absolute expression”

Question

I want to create a macro like the following:

.altmacro

.macro assert_eq a, b=%eax
    LOCAL ok
    #...
.endm

To be used as:

Answer 1

I have run into a very similar problem where I wanted to pass registers as arguments to a macro that required the use .altmacro. The fix that worked was to enclose the registers in <> and place ! before %. So try changing your macro to be

.macro assert_eq a, b=<%eax>

and if you ever want to call your macro with a register as an argument do

assert_eq <%eax>, <%ecx>