dwarves is a set of tools that use the debugging information inserted in
ELF binaries by compilers such as GCC, used by well known debuggers such as
GDB, and more recent ones such as systemtap.

Utilities in the dwarves suite include pahole, that can be used to find
alignment holes in structs and classes in languages such as C, C++, but not
limited to these.

It also extracts other information such as CPU cacheline alignment, helping
pack those structures to achieve more cache hits.

A diff like tool, codiff can be used to compare the effects changes in source
code generate on the resulting binaries.

Another tool is pfunct, that can be used to find all sorts of information about
functions, inlines, decisions made by the compiler about inlining, etc.