Panic handler crate compilation fails in debug configuration

[pacmancoder]

Hi, @MabezDev

I have the following issue:
Compilation of panic handlers (e.g. panic-abort, panic-halt) for esp8266 target fails in the debug mode with the following errors:

note: /home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s: Assembler messages:
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s:11: Error: CFI is not supported for this target
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s:12: Error: CFI is not supported for this target
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s:15: Error: CFI is not supported for this target
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s:25: Error: CFI is not supported for this target
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s: Error: unhandled local relocation fix BFD_RELOC_64
/home/pacmancoder/core/shelter-unicorn/firmware/target/xtensa-esp8266-none-elf/debug/deps/panic_abort-84b1cfdabd08f15b.panic_abort.5hi23ci5-cgu.0.rcgu.s: Error: unhandled local relocation fix BFD_RELOC_64

Interestingly enough, with release configuration it builds just fine 😕

I am building with the following commands/environment:

    export RUSTFLAGS="-C linker="$LINKER_PATH" -C target-cpu=esp8266 -C save-temps"
    xargo build --target xtensa-esp8266-none-elf

[MabezDev]

Unfortnately the current LLVM fork does not support stack frame pointers, Rust uses frame pointers to generate debug symbols (which is why it works for you in release, although Rust still doesn't guarentee frame pointers won't be used). You will have to disable them by either setting debug = false under the debug and release profiles in your Cargo.toml or using the -C debuginfo=0 compiler flag.

This means your generated binaries will have no debugging symbols in them, so you won't be able to debug with GDB (this is currently blocking me from moving foward, I've open an issue here: https://github.com/espressif/llvm-xtensa/issues/10)