makefile 中的错误：_start 的多个定义

我尝试编写一个makefile：

    CC = g++
LD = ld
CFLAGS = -Wall -std=c++0x -O3
LDFLAGS = -lgsl -lgslcblas -lpthread

SOURCES = main.cpp
OBJECTS = $(SOURCES:.cpp=.o)
EXECUTABLES = main

all: $(SOURCES) $(EXECUTABLES)
$(EXECUTABLES): $(OBJECTS)
    $(CC) $(OBJECTS) -o $@ $^ $(LDFLAGS) 

.cpp.o: 
    $(CC) $(CFLAGS) $< -o $@


.PHONY: clean
clean: 
    rm -f *~ *.o main

但是当我执行这段代码时，出现以下错误：

g++ -Wall -std=c++0x -O3 main.cpp -o main.o
main.cpp: In function ‘int main()’:
main.cpp:63:12: warning: unused variable ‘order’ [-Wunused-variable]
main.cpp:64:12: warning: variable ‘x’ set but not used [-Wunused-but-set-variable]
g++ main.o -o main main.o -lgsl -lgslcblas -lpthread 
main.o: In function `_start':
(.text+0x108): multiple definition of `_start'
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 0 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 1 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 2 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 3 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 4 has invalid symbol index 10
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 5 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 6 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 7 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 8 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 9 has invalid symbol index 2
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 10 has invalid symbol index 11
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 11 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 12 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 13 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 14 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 15 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 16 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 17 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 18 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 19 has invalid symbol index 12
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_info): relocation 20 has invalid symbol index 19
/usr/bin/ld: /usr/lib/debug/usr/lib/x86_64-linux-gnu/crt1.o(.debug_line): relocation 0 has invalid symbol index 2
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:/build/buildd/eglibc-2.15/csu/../sysdeps/x86_64/elf/start.S:109: first defined here
main.o: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.fini+0x0): first defined here
main.o:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.rodata.cst4+0x0): first defined here
main.o: In function `__data_start':
(.data+0x0): multiple definition of `__data_start'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.data+0x0): first defined here
main.o: In function `__data_start':
(.data+0x8): multiple definition of `__dso_handle'
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o:(.data+0x0): first defined here
main.o: In function `_init':
(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.init+0x0): first defined here
main.o: In function `__libc_csu_fini':
(.text+0x7f0): multiple definition of `__libc_csu_fini'
main.o:(.text+0x7f0): first defined here
main.o: In function `_start':
(.text+0x108): multiple definition of `_start'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:/build/buildd/eglibc-2.15/csu/../sysdeps/x86_64/elf/start.S:109: first defined here
main.o: In function `Lagrange_coefficient(int, double, int, int)':
(.text+0x1f0): multiple definition of `Lagrange_coefficient(int, double, int, int)'
main.o:(.text+0x1f0): first defined here
main.o: In function `__data_start':
(.data+0x80): multiple definition of `datax'
main.o:(.data+0x80): first defined here
main.o: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.fini+0x0): first defined here
main.o:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.rodata.cst4+0x0): first defined here
main.o: In function `__data_start':
(.data+0x0): multiple definition of `__data_start'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.data+0x0): first defined here
main.o: In function `Lagrange(double, double)':
(.text+0x3b0): multiple definition of `Lagrange(double, double)'
main.o:(.text+0x3b0): first defined here
main.o:(.bss+0x0): multiple definition of `std::cout@@GLIBCXX_3.4'
main.o:(.bss+0x0): first defined here
main.o: In function `__data_start':
(.data+0x8): multiple definition of `__dso_handle'
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtbegin.o:(.data+0x0): first defined here
main.o:(.dtors+0x8): multiple definition of `__DTOR_END__'
main.o:(.dtors+0x8): first defined here
main.o: In function `__libc_csu_init':
(.text+0x760): multiple definition of `__libc_csu_init'
main.o:(.text+0x760): first defined here
main.o: In function `__data_start':
(.data+0x20): multiple definition of `datay'
main.o:(.data+0x20): first defined here
main.o: In function `main':
(.text+0x0): multiple definition of `main'
main.o:(.text+0x0): first defined here
main.o: In function `_init':
(.init+0x0): multiple definition of `_init'
/usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crti.o:(.init+0x0): first defined here
/usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o:(.dtors+0x0): multiple definition of `__DTOR_END__'
main.o:(.dtors+0x8): first defined here
/usr/bin/ld: error in main.o(.eh_frame); no .eh_frame_hdr table will be created.
/usr/bin/ld: error in main.o(.eh_frame); no .eh_frame_hdr table will be created.
collect2: ld returned 1 exit status
make: *** [main] Error 1

那么，我做错了什么，该如何解决呢？如果需要，我也可以添加我的代码。 （但是当我用以下代码编译它时，代码可以工作g++ -Wall -O3 -std=c++0x $1 -lgsl -lgslcblas.
谢谢你！

  g++ main.o -o main main.o -lgsl -lgslcblas -lpthread 
      ^^^^^^         ^^^^^^

你链接main.o两次，所以其中的所有内容都是重复的。