In response to your message I just fetched doc.dtx off ctan

> 2. There's a typo on code line 395. It reads
>      |gdef|gtempa

there is no occurence of |gdef|g but one of  |gdef|@gtempa

> 4. Last, and indeed least, the checksum is wrong.

I got:
* Checksum passed *

This is using
Package: doc 1999/03/25 v2.0h Standard LaTeX documentation package (FMi)

which version do you have?

> BTW, has ever a case in which the doc checksum facility correctly detected
> that code was missing been recorded?

I'm sure Robin can give more details, but that checksum dates from a
time when files were usually transmitted by mail, and mail gateways had
a habit of turning \ into % and { into space and other horrors that I
now try to forget.....

(by the way, latex-l isn't the bug address)