HB> Is there an FCBS bug with Borland C++ 4.5?

Not that I know of; and before you ask, this isn't the FCB bug in OS/2 Warp
4 that people have encountered.  If you had suffered from that bug, your
would have seen a kernel TRAP and a dirty shutdown.

 HB> but when I run the resulting EXE, it traps with a SYS0035 error [...]

Usually an error caused by a DOS program performing an FCB file I/O call
would be returned to the program in the AX register.  It's odd that this
raises a hard error and invokes the hard error handler for the VDM.

However, one thing that is important is to _use the debugger_ and _find out
what the program is doing_.  It's no good saying "my program has an
error in it somewhere".  Get out the Borland debugger, and find out
where the error is.

Without more information, I can only make one guess, and that guess is that
you have passed an incorrectly sized or corrupted buffer to a Borland C++
for DOS library function that makes FCB calls (such as _dos_findfirst).  

 ¯ JdeBP ®

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