Nim compiler generates strange C code

[japplegame]

Look at this very strange code: 
    
    
    N_CDECL(void, NimMain)(void) {
            void (*volatile inner)(void); // <------ volatile?!! Why?
            PreMain();
            inner = NimMainInner;
            (*inner)();
    }
    
    
    Run

This code turns into strange asm (ARM v6, dangerous build):
    
    
     800002e:   4b05            ldr     r3, [pc, #20]   ; (8000044 
<NimMain+0x28>)
     8000030:   9300            str     r3, [sp, #0]
     8000032:   9b00            ldr     r3, [sp, #0]
     8000034:   f000 f808       bl      8000048 <NimMain+0x2c>
     ...
     
     8000044:   08000015        .word   0x08000015
     8000048:   4718            bx      r3
    
    
    Run

WAT?