Modifying Your makefile

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

Clang makefile

# Use Clang compiler 
	CC = clang 
# 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++ Compiler

# Use Intel C compiler 
	CC = icl 
# 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
    clang -c -O2 -fno-asm $(CFLAGS) area_functions.c 
	clean: rm -rf *o area

If your Clang 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 Clang if necessary.

In the above makefile, area_functions.c is an example of a source file that includes features unique to Clang. Since the Intel C++ Compiler uses the O2 option by default and Clang uses option O0 as the default, you instruct Clang to compile with O2. You 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
clang -c -O2 -fno-asm -std=c99 area_functions.c
icc area_main.o area_functions.o -o area