!description.txt

You can specify the underlying name for a C function the linker/compiler should actually use. If you use an existing
function's name, it will just let you refer to it with your prototype's name. If you define the function, it'll give
it that name. It even complains if a function of that name already exists. Tested with clang on a Mac, but AFAIK also
works in GCC. You can even use special characters in your function names, like you can do in assembly.

manglednames.c

extern int PrintIt(const char *format, ...) __asm("_printf");

void MyFunc( int a ) __asm("foo$barMüller");

void MyFunc( int a )
{
	PrintIt("Yay %d\n", a);
}


int main()
{
	PrintIt("Hello, world!\n");
	MyFunc(5);
	
	return 0;
}

otool.txt

(__TEXT,__text) section
foo$barMüller:
0000000100000f00	pushq	%rbp
0000000100000f01	movq	%rsp, %rbp
0000000100000f04	subq	$0x10, %rsp
0000000100000f08	leaq	0x73(%rip), %rax        ## literal pool for: "Yay %d\n"
0000000100000f0f	movl	%edi, -0x4(%rbp)
0000000100000f12	movl	-0x4(%rbp), %esi
0000000100000f15	movq	%rax, %rdi
0000000100000f18	movb	$0x0, %al
0000000100000f1a	callq	0x100000f62             ## symbol stub for: _printf
0000000100000f1f	movl	%eax, -0x8(%rbp)
0000000100000f22	addq	$0x10, %rsp
0000000100000f26	popq	%rbp
0000000100000f27	retq
0000000100000f28	nopl	(%rax,%rax)
_main:
0000000100000f30	pushq	%rbp
0000000100000f31	movq	%rsp, %rbp
0000000100000f34	subq	$0x10, %rsp
0000000100000f38	leaq	0x4b(%rip), %rdi        ## literal pool for: "Hello, world!\n"
0000000100000f3f	movl	$0x0, -0x4(%rbp)
0000000100000f46	movb	$0x0, %al
0000000100000f48	callq	0x100000f62             ## symbol stub for: _printf
0000000100000f4d	movl	$0x5, %edi
0000000100000f52	movl	%eax, -0x8(%rbp)
0000000100000f55	callq	"foo$barMüller"
0000000100000f5a	xorl	%eax, %eax
0000000100000f5c	addq	$0x10, %rsp
0000000100000f60	popq	%rbp
0000000100000f61	retq

output.txt

Hello, world!
Yay 5