[gentoo-embedded] gcc question - entry point problem in small, static app

[Christopher Friedt <chrisfriedt@gmail.com>]

I'm sure many of you have run into this problem at some point, so here goes:

I'm writing code in C for a very small static binary, and the code
doesn't use any headers or rely on any other libraries. It's quite
tiny and only does a very specific job - it initializes a uart and
repeatedly prints a message out in an infinite loop. It's intended to
be run by the bootloader instead of a kernel to test out the uart
hardware.

When I'm compiling the code, I'm using

arm-softfloat-linux-gnueabi-gcc -Wall -fomit-frame-pointer -pipe -Os
-march=armv5te -static -o hello_uart hello_uart.c

That compiles fine, but I've noticed that there is a lot of static
libc junk built into my binary, several hundred kilobytes worth of
junk, and I know for a fact that I don't need it. However, when I
build my program with options like -nostdlib -nodefaultlibs
-nostartfiles, I get an error that says

warning: cannot find entry symbol _start; defaulting to 000000000000008074

How is a program like the one below supposed to be compiled in order
to get a static, executable chunk of arm machine code?

I guess main() shouldn't even be there. Do I need to write everything
in assembler, and just link some sort of entry in a .S file, and then
link main.o with func.o ? I was sort of hoping that it would "just
work" in C without having to resort to anything slightly more tedious.

Any thoughts would be appreciated

C

==================

// some defines used in the setup and puts functions
#define X 1
#define Y 2

static void uart_puts( char * s ) {
    // puts code
}

static void uart_setup() {
    // setup uart
}

int main() {
    uart_setup();
    while(1)
        puts( "Hello, UART World!\n\r" );
     // never really returns
     return 0;
}