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From: tholen@uhccux.uhcc.Hawaii.Edu (David Tholen)
Newsgroups: comp.os.os2.programmer
Subject: LONGNAMES
Message-ID: <11355@uhccux.uhcc.Hawaii.Edu>
Date: 7 Feb 91 11:11:56 GMT
Organization: University of Hawaii
Lines: 30

Does somebody have detailed information about the contents of an OS/2 EXE
header?  Microsoft LINK version 5.03 (bundled with FORTRAN version 5.0)
does not support the LONGNAMES statement in the module definition file.  To
enable long filename support for HPFS, I've considered two options:  (1) use
the OS/2 version 1.2 linker, or (2) continue using the Microsoft linker and
edit the executable file header to flip the necessary bits.  I'm a little
reluctant to use option (1) routinely, partly because the OS/2 version 1.2
documentation doesn't have anything for LINK (either on paper or in the
on-line command reference), and partly because of the possibility of some
subtle incompatibility with the FORTRAN version 5.0 .OBJ files (or should I
not be concerned about this possibility?).

To use option (2), I need to know which bits to flip.  I tried to determine
this information on my own by comparing the output from the Microsoft and
IBM linkers, but the .EXE files were of different sizes.  Next, I tried
comparing the .EXE files produced by only the IBM linker, one done with
LONGNAMES in a .DEF file and the other done without a .DEF file.  Four bytes
were different:  offset 20 (hex) went from 0 to 1, offset B7 went from 0 to
1, offset 88 went from CE to CF, and offset 8B went from F to 10 (an increase
of 1 in each case).  Whereas the 20 and B7 bytes were the same in the output
from the Microsoft linker, bytes 88 and 8B were not, so I don't know what to
change (other than to try simply incrementing those bytes by 1).  A little
bit of experimentation showed that I could get a FORTRAN program to accept
a long filename by changing only the B7 byte, but now I'm wondering what
effect the other three bytes have and whether I need not bother with them?

Can somebody advise me in this matter?

Dave Tholen
tholen@uhifa.ifa.hawaii.edu