If we have the source file:

defb 2ah
defb '*'

it strikes me as odd that the listing looks like this:

0000 2a                            defb 2ah
0001 ..                            defb '*'

I can see good reasons for not wanting to have a messy listing by listing all the bytes for a really long string, but showing at least as many generated bytes as a normal instruction would show (i.e. 4) would seem to be a good idea.

The really old CP/M ZASM assembler, which produced very neat listings, also showed the first four hex bytes of defined strings, so the attached patch changes the listing to do this.

With this patch applied, this source:

    defb 2ah
    defb '*'
    defb '0123'
    defb 'abcdefghijkl'
    defb '*'

produces this listing:

# File test-defb.asm
0000 2a                            defb 2ah
0001 2a                            defb '*'
0002 30 31 32 33            defb '0123'
0006 61 62 63 64            defb 'abcdefghijkl'
0012 2a                            defb '*'
# End of file test-defb.asm
0013

If you wanted to indicate that a string has more than four bytes, it wouldn't be difficult to change the listing to append another '..' after the fourth byte. I'm happy to amend the patch if you'd like to do this. (ZASM didn't indicate missing bytes, but its listing format didn't have room to do so.)