Built files change if I redo cmake configuration

[atgeirr]

If I build an executable and store it, then remake that file without reconfiguration, the files compare identical. However, if I reconfigure and rebuild they differ.

Why does this happen? Is some timestamp being embedded? I think this is unfortunate behaviour, but do not know what to do about it.

[rolk]

I think this may be toolchain-dependent. On my system:

rm -rf * ; ../../src/opm-core/configure --enable-shared && ionice -c2 -n7 make -j5
cp lib/libopmcore.so libopmcoreso1.dat
make clean
ionice -c2 -n7 make -j5
cp lib/libopmcore.so libopmcoreso2.dat
../../src/opm-core/configure --enable-shared && ionice -c2 -n7 make -j5
cp lib/libopmcore.so libopmcoreso3.dat
make distclean
../../src/opm-core/configure --enable-shared && ionice -c2 -n7 make -j5
cp lib/libopmcore.so libopmcoreso4.dat
for ((i=2;i<5;i++)); do 
  cmp libopmcoreso1.dat libopmcoreso${i}.dat && echo $i: Same || echo $i: Differ;
done

produces this output:

2: Same
3: Same
4: Same

Note that ELF objects (which are used on Linux) does not have timestamps, whereas Mach-O (which is used on MacOS X) does. At which offset and how many bytes are different?

[atgeirr]

I do not know exactly where the difference is, but the file sizes are identical. I will assume this is caused by Mach-O timestamping then, and close the issue.