🚀 go-pugleaf

myao@mailhost.ecn.uoknor.edu (Minghua Yao) wrote:

>I have a C module which uses "fopen()" to open a file. When called by a C main(), the module works well and the file can be opened. But if this module is called by a TSR code (which is loaded at an interrupt not used by the DOS, and is executed by activating this interrupt), the file which does exist cannot be opened often times. Sometimes (seldom,though) the file can be opened. If so, the machine will die. The behavior seems to be undefinte.

>The working enviroment is DOS. I use 80x86 assembly for The TSR and Borland C for the C module. The C module is resident part of the TSR.

>Anybody's help will be greatly appreciated.

Dos is not reentrant. This means you can not make and calls to dos
when another dos call is already in progress.  If you do then the
results are undetermined. There are ways to determine when it is safe
to call dos and ways to set a flag so that as soon as it is ok the
dirty deed will be done then. It is rather a lot to explain but there
are many good books on the subject.

I hope I haven't insulted your intelligence but it sounds like this is
the problem if it works fine from main. l8r