Repeatable object code generation c++

Question

When I build a project using a c++ compiler, can I make sure that the produced binary is not affected if there were no changes in source code? It looks like everytime I recompile my source, the binary's md5 checksum is affected. Is the time of compilation somehow affecting the binary produced? How can I produce compilation results which are repeatable?

Answer 1

One can disassemble the binaries and run md5 on the output

Example on MacOSX

otool -tV a.out | md5
ee2e724434a89fce96aa6b48621f7220

But, one misses out on the global data...(might be a parameter to include too)

I'm answering on the problem of md5 checking a binary...how you manage your sources and build system as others have written about is also a thing to look at

Answer 2

I suspect it'll heavily depend on your toolchain and OS. For example, if one of the executable headers contains a timestamp then you're always going to find the resulting MD5 is different.

What's the end result you're trying to achieve (ie why is it so important that they're identical)..?