Repeatable checksums on object files + Shared Objects

[Jeff Kilpatrick]

Hello,

At my work place, we have a business requirement to produce
reproducible builds and build artifacts. That is, all our .o's
and .so's must have consistent checksums, when using the same compiler
and libraries, across multiple builds, with no code changes. In
practice, this works the majority of the time. We do hundreds of
builds a week with repeatable checksums.

However, from time to time, the checksums don't match. Using objdump -
x, we have isolated the problem to the index number of some symbols,
where two symbols will switch spots.

For example:
  100    Symbol1
  101    Symbol2

would appear:
  100    Symbol2
  101    Symbol1

Is there any way to take it deeper to find out why on some machines,
the symbols are in the first order, while other machines (with same
dependency, OS, compilers, etc) produce the second order? Or is their
a way to tell g++ symbols in a particular order?

Thanks,
-Jeff