Tab width oddity

[Nate Bargmann]

Although I've used Emacs on and off in the past, this time I decided to 
get serious about using it.  Editing some C source I found that in a 
struct where assignments had been lined up by other contributors and 
other editors that Emacs is making a slight mess of things.  I will try 
to explain and if needed I can post some screenshots.

My tab-stop-list is (8 16 24 32 40 48 56 64 72 80 88 96 104 112 120) and 
I am using CC-mode with indent defaults.

For example, I have a line like:

        .foo =          bar;

For most lines this lines up just fine but for some the '=' is positioned 
at a tab-stop -1 (position 7, 15, 23, etc) and the next character in the 
source file is a tab (0x09).  The character immediately following is also 
a tab.  Editors such as Vim and Midnight Commander only give the tab 
character one blank in this position and give the following tab the 
customary 8 blanks (per my settings).  However, Emacs is expanding the 
first tab to 9 blanks before showing the second tab character.  I do not 
see this occurring when a tab character is two or more characters to the 
left of the tab stop.  I first became aware of this when I found things 
were not lined up in Emacs as I had expected and a 'git diff' showed that 
my changes had moved the assignment operand to the left by one tab stop.

Neither my search of the Emacs documentation nor any amount of searching 
the Web has turned up mention of this.  Hopefully, this is not an FAQ I 
have yet to find.

Thanks,

- Nate