Vasm (http://sun.hasenbraten.de/vasm/) is a very good assembler with an active maintainer always happy to accept patches.
However it has still some (known) issues or differences with other assembler.
I have created two new patches for vasm (one bug fix with 8bits computations and the hability to have several opcodes per line), but I would like to have a feedback on them before sending them to its maintainer, in order to be sure to not break existing z80 projects and other flavors of vasm.
If you are interested, each patch is within its branch here: rgiot/unofficial_vasm_backup · GitHub (https://github.com/rgiot/unofficial_vasm_backup)
Fell free to modify or verify them with your own z80 projects.
I have also created a tool in order to test the assembler and detect regressions or new issues: cpcsdk/vasm_z80_oldstyle_eval · GitHub (https://github.com/cpcsdk/vasm_z80_oldstyle_eval)
Feel free to add new tests or adapt it to test other assemblers.
1 Like for Effort. :)