Question

can compiler options be applied selectively on my files?
I want some files to be covered by some option but not the other files.

Answer 1

Guessing that you might be using Make files:

This should get you started: Note how -fopenmp gets added just for source2.c

CC=gcc
SRC=source1.c source2.c
OBJ=$(patsubst %.c,%.o,$(SRC))
EXE=source1.exe
FLAGS= -g -O2

source2.o: FLAGS+=-fopenmp

all: $(EXE)

$(EXE): $(OBJ)
    $(CC) -o $@ $^ $(FLAGS)

%.o: %.c
    $(CC) -c -o $@ $^ $(FLAGS)

clean:
    rm $(EXE)$

Output of make -Bsn:

gcc -o source1.o source1.c -g -O2
gcc -o source2.o source2.c -g -O2 -fopenmp
gcc -o source1 source1.o source2.o -g -O2