Hi!
I just added support for reproducible builds (-frandom-seed=) into the
qbs build system.
For a automated test case I'd like to have a small snippet of C/C++
code, which definitely leads to different object files if compiled
twice.
I wasn't able to write such a snippet, so any help would be very
appreciated.
Regards,
Stephan
You could try something like this:
template
class X{}
static X<SOME_INT> x;
// or
char str[SOME_INT];
then compile it like this:
clang++ -D$RANDOM -c file.cpp -o file.o
RANDOM is a bash thing, but basically you just need to generate a random number each time you compile and pass it in as a macro.
hth…
don
sorry, typo, should be -DSOME_INT=$RANDOM
Well,
that's not exactly what I meant. In gcc, if you use -flto a c file compiled twice leads to different binaries, if you don't add -frandom-seed=<something>.
clang also supports the switch -frandom-seed=<something>, but the object files produced by clang are always binary equal.
Meanwhile I think clang intorduced -frandom-seed only for gcc compatibility:
But thanks for the hint. 
Regards,
Stephan
Sorry, didn’t read closely enough. Looks like it’s currently ignored:
$ grep -n frandom_seed include/clang/Driver/Options.td
949:def frandom_seed_EQ : Joined<[“-”], “frandom-seed=”>, Group<clang_ignored_f_Group>;