问题:

Can it be done before compiling, by comparing code? Is there any tools already doing this?

回答1:

You might find this interesting: Static analysis tool to detect ABI breaks in C++

ABI Compliance Checker — a tool for checking backward API/ABI compatibility of a C/C++ library:

abi-compliance-checker -lib NAME -old OLD.abidump -new NEW.abidump

*.abidump files are ABI dumps of OLD and NEW library versions generated by the ABI Dumper tool.

icheck - C interface ABI/API checker:

icheck --canonify -o old_version -I/usr/include/foo/ bar.h
icheck --compare -o results.txt old_version new_version

shlib-compat - ABI compatibility checker that uses DWARF debug info:

python shlib-compat -vv OLD.so NEW.so

I recall Purify had some functionality to verify compatibility between builds, take a look here.