【问题】multiple definition of `_start'

使用GCC编译器的时候，程序能够编译通过，但是结果却有问题，我查找了好多地方，还是不知道问题出在什么地方。后来才发现是因为一个变量未初始化造成的。

感觉以前在使用VS的时候很少会在这种问题上耽误时间，于是想到很少用到的-Wall 参数，我对一个正确编译通过，使用结果也是正确的程序用-Wall重新编译了一下，却出来了一堆警告和错误！如下：

test2: In function `_start':
(.text+0x0): multiple definition of `_start'
/lib/../lib64/crt1.o:(.text+0x0): first defined here
test2: In function `_fini':
(.fini+0x0): multiple definition of `_fini'
/lib/../lib64/crti.o:(.fini+0x0): first defined here
test2:(.rodata+0x0): multiple definition of `_IO_stdin_used'
/lib/../lib64/crt1.o:(.rodata.cst4+0x0): first defined here
test2: In function `data_start':
(.data+0x0): multiple definition of `__data_start'
/lib/../lib64/crt1.o:(.data+0x0): first defined here
test2: In function `data_start':
(.data+0x8): multiple definition of `__dso_handle'
/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.9.1/crtbegin.o:(.data+0x0): first defined here
test2: In function `main':
(.text+0xf8): multiple definition of `main'
/tmp/cc89iE33.o:test2.cpp:(.text+0x0): first defined here
test2: In function `_init':
(.init+0x0): multiple definition of `_init'
/lib/../lib64/crti.o:(.init+0x0): first defined here
/usr/local/lib/gcc/x86_64-unknown-linux-gnu/4.9.1/crtend.o:(.tm_clone_table+0x0): multiple definition of `__TMC_END__'
test2:(.data+0x10): first defined here
/usr/bin/ld: error in test2(.eh_frame); no .eh_frame_hdr table will be created.
collect2: error: ld returned 1 exit status

这种问题该如何解决？