C program no longer compiles on Ubuntu

Question

I made a program in C and I get these errors when compiling using gcc. I have not used them until recently, and my program has not changed.

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 slots: 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 slots: 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 slots:(.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 slots: In function `_start': (.text+0x0): multiple definition of `_start' /usr/lib/gcc/x86_64-linux-gnu/4.6/../../../x86_64-linux-gnu/crt1.o:(.text+0x0): first defined here slots: 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 /tmp/ccIlRWIn.o: In function `main': slots.c:(.text+0x0): multiple definition of `main' slots:(.text+0xe4): first defined here /usr/lib/gcc/x86_64-linux-gnu/4.6/crtend.o:(.dtors+0x0): multiple definition of `__DTOR_END__' slots:(.dtors+0x8): first defined here /usr/bin/ld: error in slots(.eh_frame); no .eh_frame_hdr table will be created. collect2: ld returned 1 exit status 

Answer 1

You forgot -o in front of the output file name so that the linker tries to use your old executable as input.

Answer 2

It seems you have more than one main and some other functions in your code. Make sure you do not include several definitions of the main file more than once in your file.

Answer 3

You could probably define the extern variable in the header file and include it in another file.

For instance,

 extern int _fini = 1; // declared in ah 

Say in a1.c or a2.c

 #include "ah" // _fini again defined in a1.c or a2.c