Created attachment 1250551 [details]
Test case

I have a package (mapnik) that is failing some tests on armv7hl since the switch to gcc 7 in rawhide while still passing on all other platforms.

I have extracted the relevant code and narrowed it down as best I can but unfortunately as it involves a boost::spirit parser the 50 lines of source expands to about 6Mb of preprocessed source :-(

Test case and preprocessed source are attached - the resulting code should not assert when run but will on armv7hl if compiled with both -O2 and -fstack-protector-strong options.

Bisecting the optimisation flags has narrowed it down to the -ftree-pre option, so this produces failing code:

  g++ -Wall -std=c++11 -O2 -fstack-protector-strong

while this produces working code:

  g++ -Wall -std=c++11 -O2 -fno-tree-pre -fstack-protector-strong