Bug 1028169

Created attachment 821291 [details]
simple test.c program

There is happening something weird with ABI compatibility of rebuilt packages in Fedora 20. The attached test.c demonstrates an issue with libical, one place I noticed (with a help of bug #1023020), but there are surely more such places - probably not only in libical.

So, to explain: Current Fedora 20 repositories has two versions of libical available. One is of version 1.0-2, another of version 1.0-3. I also rebuilt 1.0-3 as 1.0-3.1 with no change but increase the version, as a scratch
build [1]. Note that none of the rebuilds change API/ABI/SONAME/anything, it's only a new build.

Get the test.c program; its first line contains a command to build it.

Do these steps:
a1) make sure you have installed libical and libical-devel of a version 1.0-2
a2) compile the test program, verify it ends with Success
a3) copy the test to test.2

b1) update libical and libical-devel to version 1.0-3
b2) compile the test program, verify it ends with Success
b3) copy the test to test.3
b4) run test.2, it fails

c1) update libical and libical-devel to version 1.0-3.1, from [1]
c2) compile the test program, verify it ends with Success
c3) copy the test to test.3.1
c4) run test.2, it fails
c5) run test.3, it fails

It means, if I run my program with installed the same library as I compiled it in, then it works as expected, but if I run it with updated (or downgraded) version, then it doesn't work (I saw this particular function from libical succeed in some version combination, but it fails in other functions for sure).

My question is, how is it possible that the binary change causes failure, even if the package was only rebuilt and nothing else?

[1] http://koji.fedoraproject.org/koji/taskinfo?taskID=6151738