Experimental support for -D option.
Unlike normal case, with -D *grandparent* process exec's,
becoming a traced process. Child exits (this prevents traced process
from having children it doesn't expect to have), and grandchild
attaches to grandparent similarly to strace -p PID.
This allows for more transparent interaction in cases
when process and its parent are communicating via signals,
wait() etc. Without -D, strace process gets lodged in between,
disrupting parent<->child link.
* strace.c: Add global flag variable daemonized_tracer for -D option.
(startup_attach): If -D, fork and block parent in pause().
In this case we are already a child, we in fact created a grandchild.
After attaching to grandparent, grandchild SIGKILLs parent.
(startup_child): If -D, parent blocks in wait(), then
execs the program to strace. Normally (w/o -D), it is child
who execs the program.
(main): Detect -D option, call startup_attach() if it is given.
2 files changed