FATAL: BUG: Struct size mismatch:

[dongho-jung]

What I was trying to do is that hook glibc printf and puts and then print its first argument whenever the prove is triggered.
so I tried like this: sudo bpftrace -e 'BEGIN {@prev = ("","")} u:/usr/lib/libc.so.6:printf,u:/usr/lib/libc.so.6:puts / @prev != (comm, str(arg0)) / { printf("%s %s: %s\n", probe, comm, str(arg0)); @prev = (comm, str(arg0)) }' the @prev is for preventing consecutive duplicate outputs.

However if I run this, I get this error message FATAL: BUG: Struct size mismatch: expected: 128, real: 80

what did I do wrong? struct size mismatch...? I have no idea.. thanks..!

[mmisono]

The problem is the size of "" is 64 (STRING_SIZE) but the size of comm is 16 (COMM_SIZE).
https://github.com/iovisor/bpftrace/blob/45d23c82c36d2467e322e96b532edee33720c997/src/ast/passes/semantic_analyser.cpp#L97 https://github.com/iovisor/bpftrace/blob/45d23c82c36d2467e322e96b532edee33720c997/src/ast/passes/semantic_analyser.cpp#L346

(The difference comes from the fact that type of "" is char * but the comm is `char[16].)

A workaround is using comm instead of "" in the BEGIN{}.
sudo bpftrace -e 'BEGIN {@prev = (comm,"")} u:/usr/lib/libc.so.6:printf,u:/usr/lib/libc.so.6:puts / @prev != (comm, str(arg0)) / { printf("%s %s: %s\n", probe, comm, str(arg0)); @prev = (comm, str(arg0)) }

[dongho-jung]

wow thanks a lot! :D