Exception handler not working in forked child

[Yuri Dario]

When a process executes a fork(), the registered exception handlers are not working in child process. In my case, I registered EXCEPTQ 7.0 handler to dump exceptions to disk.

Registering exception handler in fork()ed code, allows testcase code to dump the exception.

[Yuri Dario]

Link to R Walsh/S Levine exception handler (with source):

​http://hobbes.nmsu.edu/download/pub/os2/dev/util/exceptq70-dev.zip

[bird]

(In [3673]) Testcase for ticket 238. references #238.

[bird]

There is nothing wrong in LIBC. The problem is that you are using DosLoadModule to load the exception handler code into the process. LIBC doesn't know about this can won't reload the module in the child address space, so the exception handler chain in the child will contain an invalid entry - bang.

[Yuri Dario]

Is there a workaround for child processes? e.g. some way to detect forking and reinstall the handler?

It seems a static library for exceptq could do the trick, but it will be still nice to use the DLL approach (e.g. licenses not compatible, or other...)

[bird]

This has nothing to do with reinstalling the handler, it is still there only the code it points to isn't there. You have to make sure the DLL is loaded into the child process one way or another.

The fix is to add

#define INCL_EXAPIS
#define INCL_EXAPIS_MAPPINGS

before including os2emx.h. An alternative is to replace DosLoadModule with dlopen.