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Fix _stack_end usage and doc #577

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Feb 9, 2025
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Fix _stack_end usage and doc #577

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12 changes: 7 additions & 5 deletions cortex-m-rt/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -67,8 +67,10 @@
//! `_stack_end` which is automatically placed after the end of statically allocated RAM.
//!
//! **NOTE:** If you change `_stack_start`, make sure to also set `_stack_end` correctly to match
//! new stack area if you are using it, e.g for MSPLIM. The `_stack_end` is not used internally by
//! `cortex-m-rt` and is only for application use.
//! new stack area if you are using it, e.g for MSPLIM.
//!
//! The `_stack_end` is checked by linker script to be less than or equal to `_stack_start` and is
//! used as a bound in `paint-stack` feature.
//!
//! For Cortex-M, the `_stack_start` must always be aligned to 8 bytes, which is enforced by
//! the linker script. If you override it, ensure that whatever value you set is a multiple
Expand Down Expand Up @@ -193,7 +195,7 @@
//!
//! ## `paint-stack`
//!
//! Everywhere between `__sheap` and `_stack_start` is painted with the fixed value
//! Everywhere between `_stack_end` and `_stack_start` is painted with the fixed value
//! `STACK_PAINT_VALUE`, which is `0xCCCC_CCCC`.
//! You can then inspect memory during debugging to determine how much of the stack has been used -
//! where the stack has been used the 'paint' will have been 'scrubbed off' and the memory will
Expand Down Expand Up @@ -573,9 +575,9 @@ cfg_global_asm! {
1:",

// If enabled, paint stack/heap RAM with 0xcccccccc.
// `__sheap` and `_stack_start` come from the linker script.
// `_stack_end` and `_stack_start` come from the linker script.
#[cfg(feature = "paint-stack")]
"ldr r0, =__sheap
"ldr r0, =_stack_end
ldr r1, =_stack_start
ldr r2, =0xcccccccc // This must match STACK_PAINT_VALUE
0:
Expand Down