Improve backtrace (#49)

src/lib.rs

@@ -83,7 +83,7 @@ fn panic_handler(info: &core::panic::PanicInfo) -> ! {
     }
     for e in backtrace {
         if let Some(addr) = e {
-            println!("0x{:x}", addr);
+            println!("0x{:x}", addr - crate::arch::RA_OFFSET);
         }
     }
 

src/riscv.rs

@@ -1,6 +1,13 @@
 use crate::MAX_BACKTRACE_ADDRESSES;
 use core::arch::asm;
 
+// subtract 4 from the return address
+// the return address is the address following the JALR
+// we get better results (especially if the caller was the last function in the calling function)
+// if we report the address of the JALR itself
+// even if it was a C.JALR we should get good results using RA - 4
+pub(super) const RA_OFFSET: usize = 4;
+
 /// Registers saved in trap handler
 #[doc(hidden)]
 #[allow(missing_docs)]

src/xtensa.rs

@@ -1,6 +1,12 @@
 use crate::MAX_BACKTRACE_ADDRESSES;
 use core::arch::asm;
 
+// subtract 3 from the return address
+// the return address is the address following the callxN
+// we get better results (especially if the caller was the last function in the calling function)
+// if we report the address of callxN itself
+pub(super) const RA_OFFSET: usize = 3;
+
 #[doc(hidden)]
 #[allow(missing_docs)]
 #[derive(Debug, Clone, Copy)]