Question

I have this output from valgrind:

==4836== 10,232 bytes in 1 blocks are still reachable in loss record 1 of 1
==4836==    at 0x4C2779D: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4836==    by 0x401865: thrt() (main.cpp:221)
==4836==    by 0x4048B1: main (tester.cpp:35)

1. what does ==4836== mean?
2. what does 0x4C2779D mean?

Answer 1

The answer to your first question: that number represents the process ID.

Look at the official source.

From this same source, we can see the answer to your second question:

The code addresses (eg. 0x804838F) are usually unimportant, but occasionally crucial for tracking down weirder bugs.