Add option to change signals

[Bojun-Seo]

heaptrace use SIGUSR1 and SIGUSR2 to dump allocation status (in terms of size and count respectively) during process running.
But the signal handler will not work properly, if the target process uses one or both of the signals.

So I suggest to add option to change signals to dump allocation status.
For example, (only to show the intention not an actual option format)

# register signal 33 to dump the allocation status sorted in terms of size
./heaptrace --signal size:33 ./a.out

# register signal 34 to dump the allocation status sorted in terms of count
./heaptrace --signal count:34 ./a.out

# register signal 33 and 34 to dump the allocation status sorted in terms of size and count
./heaptrace --signal size:33 --signal count:34 ./a.out

[honggyukim]

Yes, that's doable, but we can also support signal name as well as signal number.

For example, the following commands do the same thing.

$ heaptrace --signal size:27 ./a.out

$ heaptrace --signal size:SIGPROF ./a.out

The signal number of SIGPROF is 27. Would you like to implement it?

[Bojun-Seo]

Yes, I'd like to implement it

[Bojun-Seo]

I suggested to register multiple keys like followings:

./heaptrace --signal size:33 --signal count:34 ./a.out

But how about registering multiple keys like this?(comma separate)

./heaptrace --signal size:33,count:34 ./a.out

Whatever the signal option interface looks like, I'm thinking about to set HEAPTRACE_SIGNAL environmental variable like following.
HEAPTRACE_SIGNAL=size:33,count:34
The second form make it easy to fabricate this environmental variable.
And some users may want to use libheaptrace.so directly after setting environment variables. The second form would be more intuitive for this kind of users as well.

Or

We could think about another form to set environmental variable.

Or

We could think about to allow only one signal and sort key pair can be set.

[Bojun-Seo]

I almost implement this feature except to convert SIGXX into corresponding signal number. It seems very hard to do this neatly. So I suggest to support only signal numbers, not signal macro names.

[honggyukim]

You can simply use the std::map as follows.

std::map<std::string, int> signum = {
        {"SIGHUP", 1},
        {"SIGINT", 2},
        {"SIGQUIT", 3},
        {"SIGILL", 4},
        {"SIGTRAP", 5},
        {"SIGABRT", 6},
        {"SIGBUS", 7},
        {"SIGFPE", 8},
        {"SIGKILL", 9},
        {"SIGUSR1", 10},
        {"SIGSEGV", 11},
        {"SIGUSR2", 12},
        {"SIGPIPE", 13},
        {"SIGALRM", 14},
        {"SIGTERM", 15},
        {"SIGSTKFLT", 16},
        {"SIGCHLD", 17},
        {"SIGCONT", 18},
        {"SIGSTOP", 19},
        {"SIGTSTP", 20},
        {"SIGTTIN", 21},
        {"SIGTTOU", 22},
        {"SIGURG", 23},
        {"SIGXCPU", 24},
        {"SIGXFSZ", 25},
        {"SIGVTALRM", 26},
        {"SIGPROF", 27},
        {"SIGWINCH", 28},
        {"SIGIO", 29},
        {"SIGPWR", 30},
        {"SIGSYS", 31},
};

[honggyukim]

/usr/include/asm-generic/signal.h says the SIGRTMIN and above should not be considered constants, which means the signal number might be different depending on the systems so we can't support it.
https://github.com/torvalds/linux/blob/v6.6/include/uapi/asm-generic/signal.h#L49-L50

[Bojun-Seo]

You are right, so I updated PR without supporting signal definition string.

[Bojun-Seo]

I discussed about the option format with my coworkers and followings are the suggested candidates.

heaptrace --signal size:33,count:34 ./a.out
heaptrace --signal size:33 --signal count:34 ./a.out
heaptrace --sig-size 33 --sig-count 34 ./a.out
heaptrace --signal 33,34 ./a.out // set sort key implicitly, size for 33 and count for 34
heaptrace --signal ,34 ./a.out // In case to set count for 34 only
heaptrace --signal 33, ./a.out // In case to set size for 33 only
heaptrace --SIG 33,34 ./a.out // upper or lower
heaptrace --sig-for-size 33 --sig-for-count 34 ./a.out
heaptrace --sig4size 33 --sig4count 34 ./a.out
heaptrace --signal s:33,c:34 ./a.out