Hi Jonathan, thanks for the definitive answers. > On 4 March 2013 19:01, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > > On 4 March 2013 16:48, <Heiko.Papenfuss@xxxxxxxxxxx> wrote: > > > 2.) [1] states that starting with GCC 3.2, there is a default C++ ABI (the > > vendor-neutral C++ ABI) that GCC tries to adhere to. However, there is not > > a hint of which versions did or did not, or with which versions of GCC an > > incompatible change of the ABI has happened. > > The manual for each version tells you the default value for -fabi-version I noticed that but being confused with the library ABI issue and by some posts on the internet that seemed to indicate otherwise, I did not trust it as much as I should have. > > [3] indicates then that "It's pretty easy to see when the ABI has changed > > because we bump the major release number in the soname." of libstdc++.so > > and as one can figure out looking at [2], this has not happened since > > libstdc++.so.6.0.0, which came with GCC 3.4.0. From that, I am willing to > > draw the conclusion that the compiler ABI has been stable since then. Is > > this correct and is it therefore save to say that a library compiled with > > GCC 3.4.x can be linked against (dynamically or statically) with GCC > > 4.y.z, if we assume that all ABI-affecting compiler flags have been the > > same (esp. -fabi-version=2)? > > Yes. (Technically if the object files were compiled with > ABI-compatible GCC versions then what matters at link-time is not > which version of GCC you use to do the link, it's which version of > libstdc++.so you link against, but that is usually determined by the > version of GCC used, unless you specifically force GCC to link to a > different libstdc++.so) Does this mean that it would be possible to link with any GCC that supports -fabi-version=2 against any libstdc++.so.6.x.y? > > > Does the reverse hold, too? > > What is the reverse case? If you are asking whether a library > compiled with GCC 4.x can be linked against using GCC 3.4 the answer > is no, libstdc++.so ABI compatibility only goes backwards, not > forwards. > > If any object in your program (or any object in any library it links > to) was compiled with GCC version X then at run-time the program must > be linked to the libstdc++.so from GCC X or later. You cannot compile > with GCC X then use libstdc++.so from GCC X-1 at run-time. > That was the question, yeah. Another question comes to my mind here: Let's assume I have two object files or libraries that have been compiled separately and were compiled with different versions of GCC thus needing different versions of libstdc++.so at run-time. Do I read [2], "Multiple ABI Testing", correctly that I should be able to compile and run a program which uses both libraries provided that the most current libstdc++.so that any library depends on is present at run-time? Heiko
