title: Error in makefile: multiple definition of _start
body: <p>I have tried to write a makefile:  </p>
  
  <pre><code>    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) $&lt; -o $@
  
  
  .PHONY: clean
  clean: 
      rm -f *~ *.o main
  </code></pre>
  
  <p>But when I am executing this code, I get the following errors:</p>
  
  <pre><code>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
  </code></pre>
  
  <p>So, what am I doing wrong, and how can I fix it? If requested I can add my code, too. (But the code works when I am compiling it with <code>g++ -Wall -O3 -std=c++0x $1 -lgsl -lgslcblas</code>.<br>
  Thank you!</p>