modify addr-exp [ , byte-size ]

The specified address range has been modified. This is the older watchpoint facility.

addr-exp is any expression that can be evaluated to produce an address. If a symbolic expression is used, the size of the region to be watched is automatically deduced, or you can override that with the `,` syntax. You can also use nonsymbolic, typeless address expressions; in which case, the size is mandatory. For example:

stop modify 0x5678, sizeof(Complex)

Limitations of modify event-spec on Solaris 2.5.1

Addresses on the stack cannot be watched.

The event does not occur if the address being watched is modified by a system call.

Shared memory (MAP_SHARED) cannot be watched, because dbx cannot catch the other processes stores into shared memory. Also, dbx cannot properly deal with SPARC swap and ldstub instructions.

Addresses that do not exist at the time a handler for this event is created cannot be watched.

Multithreaded applications are prone to deadlock so mt watchpoints are nominally disallowed. They can be turned on by setting the dbx environment variable mt_watchpoints.