Valgrind reporting a segment overflow

Question

When running my program with valgrind / callgrind I get the following message a lot:

==21734== brk segment overflow in thread #1: can\'t grow to 0x4a39000

Answer 1

While this is not really an answer, it still satisfies OP's "couldn't find any docs" requirement:

1) http://repo.or.cz/valgrind.git/blob/HEAD:/coregrind/m_syswrap/syswrap-generic.c

contains the message discussed at line 1322

2) http://sourceforge.net/p/valgrind/mailman/message/34068401/

is the commit that introduced the feature, and the corresponding commit message reads

Author: florian
Date: Wed Apr 29 13:59:16 2015
New Revision: 15155

Log: Issue an error message if then brk segment overflows.

from where we can further relay this question on to those who can give a qualified answer to "what exactly does "a brk segment overflows" mean in this context"!