Modifying Your makefile

If you use makefiles to build your gcc application, you need to change the value for the GCC compiler variable to use the Intel® C++ compiler. You may also want to review the options specified by CFLAGS. A simple example follows:

gcc makefile

  # Use gcc compiler 
CC = gcc 
  # Compile-time flags 
CFLAGS = -O2 -std=c99 
all: area_app 
area_app: area_main.o area_functions.o
    $(CC) area_main.o area_functions.o -o area 
area_main.o: area_main.c
    $(CC) -c $(CFLAGS) area_main.c 
area_functions.o: area_functions.c
    $(CC) -c -fno-asm $(CFLAGS) area_functions.c 
clean: rm -rf *o area

Modified makefile for Intel® C/C++ Compiler

# Use Intel C compiler 
CC = icc 
# Compile-time flags 
CFLAGS = -std=c99 
all: area-app 
area-app: area_main.o area_functions.o
    $(CC) area_main.o area_functions.o -o area 
area_main.o: area_main.c
    $(CC) -c $(CFLAGS) area_main.c 
area_functions.o: area_functions.c
    gcc -c -O2 -fno-asm $(CFLAGS) area_functions.c 
clean: rm -rf *o area

If your gcc code includes features that are not supported with the Intel® C++ compiler, such as compiler options, language extensions, macros, pragmas, and so on, you can compile those sources separately with gcc if necessary.

In the above makefile, area_functions.c is an example of a source file that includes features unique to gcc. Since the Intel C++ Compiler uses the O2 option by default and gcc uses option O0 as the default , we instruct gcc to compile with O2. We also include the -fno-asm switch from the original makefile since this switch is not supported with the Intel C++ Compiler. With the modified makefile, the output of make is:

icc -c -std=c99 area_main.c
gcc -c -O2 -fno-asm -std=c99 area_functions.c
icc area_main.o area_functions.o -o area