[Exim] confused about exim_group in exim 3.33

Using exim 3.33 I have defined numeric values for EXIM_USER and EXIM_GROUP.
I check this by using exim -bP and look for the equivalent runtime values
and I think the compile time options are in effect; exim prints out the
equivalent names from our passwd and group files for the numeric values.

I should point out that for historical reasons the passwd entry for "Mr Exim"
has a different primary group number ( lets call it N ) from EXIM_GROUP.


OK so far ... now I try to deliver to a pipe, hoping the program will run
by default as the EXIM_GROUP.

Actually we have set up the program ( let's call it "mailman" ) in the
hope that it will run as the EXIM_GROUP.

Looking at the -d9 output things go quite well, with debugging output
showing gid=<EXIM_GROUP> for quite a while, until it is about to deliver
when all of a sudden some lines inside df_generated.c print out bad news
in the form of gid=N ... where N is the number I first thought of when
creating the exim user (which was before we realised having an exim group
was a good idea).

Does the above seem correct behaviour? I am surprised to see the compiled
in value used to start with and then the passwd file entry take over.


Now to verify, if I change the N value in the password file to the same
value as EXIM_GROUP in the build-time configuration, then as you'd guess
the pipe is run under this new N value as the group ID.


Any explanations please?
Thanks,
Steve