Bug#887880: Different results for g++-4/5 vs g++-6/7

[Steffen Möller]

Dear Aurelien,

The package compiles just fine with the later gcc version. But - and 
this is a big but - about 10 to 25 percent of results produced with the 
newer versions give slightly different results, i.e. different enough 
that the difference between the g++ versions is bigger than the 
difference between platforms (ARM, 32bit annd 64bit Intel and AMD 
machines, ARM and Intel with an OpenCL implementation).

I would not have found that compiler dependency if g++-5 had already 
been completely removed from the distribution. So, I am really thankful 
for that. It was not expected. I can see that you want to remove that 
older gcc, but I think it would be a mistake. I do not say that the 
newer version has an issue, that may or may not be the case, just be 
aware that the binaries at hand have been tested against against 
injected known truths and error tolerance thresholds been derived from 
there. This needs more investigation. Please do not remove this package 
or g++-5 yet.

Cheers,

Steffen