Flags to enable thorough and verbose g++ warnings

-pedantic -Wall -Wextra -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wlogical-op -Wmissing-declarations -Wmissing-include-dirs -Wnoexcept -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wsign-conversion -Wsign-promo -Wstrict-null-sentinel -Wstrict-overflow=5 -Wswitch-default -Wundef -Werror-Wno-unused

General warning options and C++ options (scroll down to the bottom for warnings)

A good base setup for C is:
-std=c99 -pedantic -Wall -Wextra -Wwrite-strings -Werror
and for C++
-ansi -pedantic -Wall -Wextra -Weffc++

My C++ version:

-g -O -Wall -Wextra -Weffc++ -pedantic -Wformat=2 \
 -Waggregate-return -Wcast-align \
 -Wcast-qual   -Wconversion \
 -Wdisabled-optimization  -Wfloat-equal   \
 -Winit-self  -Winline \
 -Winvalid-pch   -Wunsafe-loop-optimizations  -Wmissing-braces \
 -Wmissing-format-attribute   \
 -Wmissing-include-dirs \
 -Wpacked  -Wpadded -Wpointer-arith \
 -Wredundant-decls -Wshadow  -Wstack-protector \
 -Wswitch-default  -Wswitch-enum \
 -Wunknown-pragmas  -Wunreachable-code -Wunused \
 -Wvariadic-macros  -Wwrite-strings \
 -Wlogical-op -Wsign-conversion  \
 -Wstrict-overflow=5 -Wundef