Help!!!!!!!!!
krn.c
void _start(void)
{

int a;
a=1;
}


boot.asm
format ELF
extrn '_start' as _start
section '.text'
jmp _start

and try it this command
fasm boot.asm
tcc -nostdlib -nostdinc -wl,--oformat,elf32-i386 krn.c
tcc -r -o test.o krn.o boot.o

but entry-point start krn.c
i want this after compile

jmp _start
_start:
int a;
a=1;


how compile binary file?????

I've briefly touched on this elsewhere but not without modifying TCC. I can't remember exactly what it was I had to do but if I remember correctly, the PE linker won't create a binary and the ELF linker even though it has been told to create a binary, still sticks the dynamic interpreter section at the start of the file. Tell it to link at a particular address and you'll also end up with up to 4K of padding up to a page boundary at the start. I really must find those sources if people are starting to show interest.
Theoretically, according to the manual it should be possible with certain command line flags but in practice, Fabrce Bellard moved on to develping FFDSHOW and PLEX86.
I'd actualy compiled a working bootloader and was part way through paged memory management when I got bored. I was develping the basic algorithms in 'C' and then migrating to assembler.

Ooops.. Qemu..