"Invalid value for -O" build failure(s) — clang 3.9.1

clang refuses the command:
$ clang -O6 main.c
(gcc accepts it even if it is meaning less)
PackageVersionSupposed error messageFull log Bug report
basemap 1.0.7+dfsg-4error: invalid integral value 'g' in '-Og' Log
cython 0.25.2-1error: invalid integral value 'g' in '-Og' Log
gamera 1:3.4.2+git20160808.1725654-1error: invalid integral value 'g' in '-Og' Log
matplotlib 2.0.0+dfsg1-2error: invalid integral value 'g' in '-Og' Log
pillow 4.1.1-3error: invalid integral value 'g' in '-Og' Log
pillow-sane 2.8.3-1error: invalid integral value 'g' in '-Og' Log
psycopg2 2.7.1-1error: invalid integral value 'g' in '-Og' Log
pygpgme 0.3-1.2error: invalid integral value 'g' in '-Og' Log
pyicu 1.9.5-1error: invalid integral value 'g' in '-Og' Log
pyodbc 3.0.10-2error: invalid integral value 'g' in '-Og' Log
python-bsddb3 6.1.0-1error: invalid integral value 'g' in '-Og' Log
python-djvulibre 0.8-1error: invalid integral value 'g' in '-Og' Log
python-levenshtein 0.12.0-2error: invalid integral value 'g' in '-Og' Log
python-reportlab 3.4.0-3error: invalid integral value 'g' in '-Og' Log
python3-stdlib-extensions 3.5.3-2error: invalid integral value 'g' in '-Og' Log
twisted 16.6.0-2error: invalid integral value 'g' in '-Og' Log

16 errors