White space being inserted before a semicolon in asm-mode

Question

When I try to insert a semicolon in my code (in asm-mode) it seems to indent a certain number of tabs like this (usually 4 it seems):

D               ;

And if I put another semicolon on the next line it will indent one tab so it looks like this and add another semicolon even though I only pressed it once:

D               ;
    ;; 

I am sure this is some helpful auto-complete technique, but I am just trying to do commands with a semicolon inside of it like 0;JEQ but since I am an Emacs noob I don't know where to look to deactivate this. I searched with different queries looking for this problem, but I am having trouble finding it which is weird since everything else I looked up was easily answerable either from the Emacs manual or some other site. Can anyone point me to which option I can change so no white space is inserted?

Edit: Here is what option I changed my comment button to:

Is this correct? Basically, I just deleted the comment char which was ";" to what it is now which is "/", but like I say the same problem happens where when I press the semicolon key I get a slash instead and my slash key still gives me a slash.

Answer 1

In asm-mode, C-hk; reports that ; is bound to asm-comment.

The Commentary for asm-mode.el (M-x find-library RET asm-mode RET) says:

This minor mode is based on text mode.  It defines a private abbrev table
that can be used to save abbrevs for assembler mnemonics.  It binds just
five keys:

        TAB             tab to next tab stop
        :               outdent preceding label, tab to tab stop
        comment char    place or move comment
                        asm-comment-char specifies which character this is;
                        you can use a different character in different
                        Asm mode buffers.
        C-j, C-m        newline and tab to tab stop

Code is indented to the first tab stop level.

This mode runs two hooks:
  1) An asm-mode-set-comment-hook before the part of the initialization
depending on asm-comment-char, and
  2) an asm-mode-hook at the end of initialization.

So the variable asm-comment-char defines the comment character, and the mode uses this value to bind the associated key to the asm-comment command (i.e. "place or move comment").

You can configure this value globally via M-x customize-option RET asm-comment-char RET

Exactly how this feature works is entirely up to how the mode is written. In this case I can see that when the asm-mode function is called it generates a new local keymap for the buffer which inherits from asm-mode-map, and it defines the comment key in there.

Immediately before it does that it runs asm-mode-set-comment-hook, so one could also set a value for asm-comment-char (potentially a buffer-local value) using that hook, instead of customizing the option globally.

All of this commenting configuration happens when the asm-mode function runs, so changing the global value doesn't affect existing asm-mode buffers; but you could just run M-x asm-mode in a buffer to get it to pick on on a change to asm-comment-char, or you could revert the buffer(s), or re-visit them.

e.g.:

• M-x revert-buffer
• or kill the buffer and re-visit it
• or use something like M-x ibuffer to mark and revert buffers en-masse

In ibuffer that would be *M asm-mode RET to mark, and V to revert.

Note that the way the keymap is generated means that each asm-mode buffer has its own independent comment key binding, so reverting a single buffer will not affect the pre-existing comment bindings in other asm-mode buffers, so reverting them all after a change to the global comment char option would make sense.

Answer 2

A quick hack to disable this confusing functionality entirely is:

(advice-add #'asm-comment :override #'self-insert-command)

Then pressing your comment character will just insert it like you were expecting.