math.h refer failure when compile LinSched 3.3 under 64-bit Ubuntu12.04 - linux

Question

Compiling the LinSched 3.3 under 64-bit Ubuntu-12.04 throws me the following errors:
******/home/xxxxx/Desktop/linsched_3.3/tools/linsched/tests/linsched_rand_test.c:169: undefined reference to `sqrt'
collect2: ld returned 1 exit status
make[1]: [linsched_rand_test] Error 1
make[1]: Leaving directory `/home/jianguo/Desktop/linsched_3.3/tools/linsched/tests'
make: [all] Error 2*
Seems there is a problem when refer/link to the math.h, which is:
math: /usr/include/math.h
From the make file of LinSched 3.3, the CFLAGS and LFLAGS are defined as follows,
CC = ${CROSS_COMPILE}gcc
CFLAGS = -g -O2 -m64 -D__KERNEL__ -D__LINSCHED__ -Wall -Wundef -Wstrict-prototypes \
-Werror-implicit-function-declaration -fno-common \
-I${LINSCHED_DIR}/include -I${LINUXDIR}/include \
-I${LINUXDIR}/arch/linsched/include -I${LINSCHED_DIR}/ \
-include ${LINSCHED_DIR}/include/generated/autoconf.h \
-Wno-pointer-sign -include ${LINUXDIR}/include/linux/kconfig.h
CFLAGS_LINUX = $(CFLAGS) -nostdinc -isystem $(shell $(CC) -print-file-name=include) \
-include ${LINSCHED_DIR}/linux_linsched.h \
-Wno-unused -Wno-strict-aliasing
LFLAGS = -lm
....
...
...
LD_PERCPU = ${LD} -r -T ${LINSCHED_DIR}/linsched.lds
OBJ_FILES = ${LINSCHED_OBJS} ${LINUX_OBJS}
DEPS := ${OBJ_FILES:.o=.d}
-include ${DEPS}
TIME_HDR=${LINUXDIR}/kernel/timeconst.h
${TIME_HDR}: ${LINUXDIR}/kernel/timeconst.pl
#echo "(Generating timeconst.h)"
#perl ${LINUXDIR}/kernel/timeconst.pl 1000 > $#
${LINUX_OBJS}: %.o: %.c ${TIME_HDR}
#echo "CC KERNEL $<"
#${CC} -o $# ${CFLAGS_LINUX} -c $< -MMD
%.o: %.c
#echo "CC SIM $<"
#${CC} ${CFLAGS} -o $# -c $< -MMD
Someone on the web suggested to add -lm into the CFLAGS, I tried to insert the -lm parameter to several places of the CFLAGS, but the same errors persist.
Any idea ???
BTW, I compiled the LinSched 3.3 under 64-bit ubuntu becasue in the CFLAGS it is configured as -m64. And a former compile under 32-bit Ubuntu throws me error of data incompatibility(between elf64-x86-64 and elf32-i386)
As suggested by #another.anon.coward, I checked how the LFLAGs is used later, and find it is vever used. As a solution, how should I modify the makefile to add the LFLAGS parameter ???

Answer 1

Actually the issue was that linker flag ${LFLAGS} was used in /tools/linsched/tests/Makefile incorrectly.
Here is the patch that fixes the math library link related build issue for linsched:
diff --git a/tools/linsched/tests/Makefile b/tools/linsched/tests/Makefile
index 91bb8eb..8074c93 100644
--- a/tools/linsched/tests/Makefile
+++ b/tools/linsched/tests/Makefile
## -33,7 +33,7 ## TEST_DEPS := ${TESTS:%=%.d}
${TESTS}: ${OBJ_FILES} $$#.o
#echo CC TEST $#
#${LD_PERCPU} -o $#.percpu $^
- #${CC} ${LFLAGS} -o $# $#.percpu -MMD
+ #${CC} -o $# $#.percpu ${LFLAGS} -MMD
#rm $#.percpu
clean: