Chap3 pre-proocess

.... pre process (cc1, pcc)

`gcc -print-prog-name=cc1` -E -H -quiet hello_define.c > /dev/null

so as to observe include info

cc1 -quiet
cc1 -E .. exec pre-processing (re-direct to stdout)
cc1 -H .. show more detail include info (re-direct to stderr)
cc1 -v

`gcc -print-prog-name=cc1` -E -M -quiet hello_define.c

so as to see header files

cc1 -M .. Makfile option

gcc -print-prog-name=xxx (ex =cc1)
gcc -Wall -W -Werror

which cpp
cpp -v < /dev/null
cpp -nostdinc -v < /dev/null
cpp -nostdinc -v -I/usr/include .. add "system Header files"

cpp -nostdinc -I./a -I- -I./b -v < /dev/null .. -I- works as separeter,
./a part shuld be "local", -b part should be "local"/"system"

cpp -nostdinc -I./ -I./a -I- -I./b -v < /dev/null

cpp -dM < /dev/null .. show defined micros.

#if
..
#else
..
#endif