Bug#876825: gcc: infinite loop targeting armel

[Edmund Grimley Evans <edmund.grimley.evans@gmail.com>]

Package: gcc-6-arm-linux-gnueabi
Version: 6.3.0-18cross1

This is not specific to cross-compiling and not even to gcc-6.

We noticed the infinite loop when the buildd tries to build rnahybrid:

https://buildd.debian.org/status/logs.php?pkg=rnahybrid&arch=armel

It seems to be easy to reproduce with the cross-compiler. On Debian
amd64 Stretch:

sudo apt-get install gcc-6-arm-linux-gnueabi
apt-get source rnahybrid
cd rnahybrid-2.1.2/
export CC=arm-linux-gnueabi-gcc-6
./configure --host=xx
make
# cc1 runs forever with 100% CPU, not much memory, compiling "energy.c"

There's a warning about undefined behaviour, and I've not looked at
the source at all, but an infinite loop like this is presumably a GCC
bug in any case (though perhaps not such a serious one if it only
happens with code that invokes undefined behaviour).