First of all: I'm sorry if this is the wrong place to ask, but at least it's related to the book :)
While reading the Embedonomicon I wrote some bare metal stuff without using any crate. Just for learning how everything works together. I didn't find out why this source code:
// Copy DATA
let mut sdata = &mut _sdata as *mut u32;
let edata = &mut _edata as *mut u32;
let mut sidata = &_sidata as *const u32;
while sdata < edata {
ptr::write(sdata, ptr::read(sidata));
sdata = sdata.offset(1);
sidata = sidata.offset(1);
}
was compiled to this assembly (copied from gdb):
│ 0x8000026 <rustymc::run+18> ldmia r1!, {r2} │
│ 0x8000028 <rustymc::run+20> stmia r0!, {r2} │
│ >0x800002a <rustymc::run+22> b.n 0x8000026 <rustymc::run+18> │
An endless loop which will write to invalid memory sooner or later.
I boiled it down to a minimal program which is attached. I used rustc 1.47.0 and cargo run --release.
What's wrong with my code?