Error: linking with avr-gcc failed

[jonahbron]

I'm working on a program that uses @Rahix's avr-hal and the w5500 driver crate. However when compiling, I get this error:

$ export RUST_TARGET_PATH="/home/jonah/Projects/smart-plug/"
$ export RUSTUP_TOOLCHAIN=avr-toolchain
$ export XARGO_RUST_SRC="/home/jonah/Projects/rust/src"
$ xargo build --target avr-atmega328p --release
error: linking with `avr-gcc` failed: exit code: 1
  |
  = note: "avr-gcc" "-Os" "-mmcu=atmega328p" "-L" "/home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib" "/home/jonah/Projects/smart-plug/target/avr-atmega328p/release/deps/smart_plug-c760f2efbebaee9b.smart_plug.17dox426-cgu.0.rcgu.o" "-o" "/home/jonah/Projects/smart-plug/target/avr-atmega328p/release/deps/smart_plug-c760f2efbebaee9b.elf" "-Wl,--gc-sections" "-L" "/home/jonah/Projects/smart-plug/target/avr-atmega328p/release/deps" "-L" "/home/jonah/Projects/smart-plug/target/release/deps" "-L" "/home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib" "-Wl,--start-group" "-Wl,--end-group" "-Wl,-Bstatic" "/home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib" "-Wl,-Bdynamic" "-Wl,--gc-sections"
  = note: /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_24':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x35c): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_26':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x37c): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_51':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x7ee): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_65':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x924): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_89':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xbde): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_101':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xcfc): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB4_103':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xd22): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB12_17':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x2df6): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB12_23':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x2e52): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x2e64): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB18_17':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x5e84): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB18_23':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x5ee0): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x5ef4): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB24_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x89c2): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB24_12':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x89dc): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB25_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x8aa6): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB26_8':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x8bfc): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB30_8':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x9210): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB30_10':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x921a): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB31_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x92da): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB32_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x940e): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB36_76':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xa2f0): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB36_78':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xa352): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB39_46':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc024): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc044): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc056): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc070): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB39_75':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc526): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB39_78':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xc5a6): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB48_3':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xdebc): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB62_53':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0xfd98): undefined reference to `__divmodti4'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB64_49':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1091e): undefined reference to `__divmodti4'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB74_6':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11b7a): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11b8c): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11ba2): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB74_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11bb4): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB75_6':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11c50): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11c60): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11c76): undefined reference to `__ashrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB75_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11c88): undefined reference to `__ashrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB76_6':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11d5e): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11d6e): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11d84): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB76_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x11d96): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB83_21':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x12dc2): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x12dd6): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB84_21':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x134a4): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x134c2): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB85_24':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x13bda): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x13bf6): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB90_93':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x15668): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `_$LT$i32$u20$as$u20$compiler_builtins..int..Int$GT$::wrapping_shl::h538766759685e63f':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x18eba): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB148_9':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1aa00): undefined reference to `__divmodti4'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB149_9':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1ac50): undefined reference to `__divmodti4'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `_$LT$u32$u20$as$u20$compiler_builtins..int..WideInt$GT$::wide_shift_left::h2260981b3eb5ef04':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b7fa): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b814): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b83a): undefined reference to `__ashlsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB169_3':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b8e0): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b8f8): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b914): undefined reference to `__ashlsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b942): undefined reference to `__lshrsi3'
          /home/jonah/.xargo/lib/rustlib/avr-atmega328p/lib/libcompiler_builtins-9a1ff32ee7e2d645.rlib(compiler_builtins-9a1ff32ee7e2d645.compiler_builtins.d7w6r55k-cgu.0.rcgu.o): In function `LBB169_7':
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b984): undefined reference to `__lshrsi3'
          compiler_builtins.d7w6r55k-cgu.0:(.progmem.data+0x1b99c): undefined reference to `__ashlsi3'
          collect2: error: ld returned 1 exit status
          

error: aborting due to previous error

Because these clearly aren't normal Rust compiler errors, it seems like this might be a bug with the Rust compiler itself. Does anything obvious stand out as a problem here? Could there be a problem with my setup? I just updated and re-compiled avr-rust today to make sure. Note that this error only occurs if I invoke the receive method of w5500 in my application. Full application code can be found here:

https://github.com/jonahbron/smart-plug/tree/c9f8994

[Rahix]

This error often occurs if your program size overflows the flash size. Are you building in release or debug mode?

[Rahix]

Sorry, should have read more carefully ... It seems you are already building in release mode, so the compiler is doing its best to optimize out everything it can. Somewhere along the call-graph you are pulling in code which bloats the binary so much that it no longer fits into flash. A common candidate for this is core::fmt.

I'm not sure what the best way is to find out where this issue comes from. Personally, I'd use one of these:

1. Try commenting out parts until you find the one responsible. In this case, the code you linked contains a few references to core::fmt, they might be good candidates.
2. Try building with rustc --emit=obj and analyze the symbol sizes with nm --print-size --size-sort.

[jonahbron]

Ah, that seems like a good place to start, thank you @Rahix . Would it be appropriate to alter the compiler so that it can catch that sort of problem and provide a clearer error message?

[jonahbron]

@Rahix Do you know if there's a way to alter the target descriptor to trick it into thinking there's more space? At least it would let me confirm that it's a size constraint issue.

[Rahix]

Would it be appropriate to alter the compiler so that it can catch that sort of problem and provide a clearer error message?

Not really possible as final sizes are only known at link time.

Do you know if there's a way to alter the target descriptor to trick it into thinking there's more space?

You could write your own linker script, but I don't think the effort is worth it. Try compiling with --emit=obj, you'll see pretty quickly where the bloat comes from.

[jonahbron]

@Rahix I'm having trouble figuring how how to follow your instructions. Currently my command to compile is

xargo build --target avr-atmega328p --release

So I tried altering it to be

xargo rustc --target avr-atmega328p --release -- --emit=obj

But it ends up giving the same error. It seems like nm is expecting some sort of file, but I don't know where to find the file supposedly being output by emit=obj.

[Rahix]

It should be an object file (.o), somewhere in target/avr-atmega328p/release. It should still be emitted, even if you get the error during linking.

[jonahbron]

Thanks so much for your help @Rahix . I find the file and got the output.

00000000 00000001 B DEVICE_PERIPHERALS
0000119c 00000002 r rust_begin_unwind
00000000 00000002 r __unnamed_3
00000008 00000002 r _ZN4core3ptr18real_drop_in_place17h671565532a8ec42eE
0000000a 00000002 r _ZN4core3ptr18real_drop_in_place17h84aaf412b5654cb2E
00000000 00000004 r _ZN112_$LT$embedded_hal..digital..v1_compat..OldOutputPin$LT$T$GT$$u20$as$u20$embedded_hal..digital..v1..OutputPin$GT$7set_low17ha964da085e52de99E
00000004 00000004 r _ZN112_$LT$embedded_hal..digital..v1_compat..OldOutputPin$LT$T$GT$$u20$as$u20$embedded_hal..digital..v1..OutputPin$GT$8set_high17h53da3a0de33410acE
000011a6 00000008 r _ZN4core9panicking5panic17h5dbe8e19a91fe7ddE
0000119e 00000008 r _ZN4core9panicking9panic_fmt17h88f68b20b00f166eE
00000000 0000000a d __unnamed_1
00000000 0000000a d __unnamed_2
00001190 0000000c r _ZN84_$LT$atmega328p_hal..spi..Spi$u20$as$u20$embedded_hal..spi..FullDuplex$LT$u8$GT$$GT$4read17h7ffa6261298b29e9E
00000000 00000019 r switch.table._ZN5w55008Register12control_byte17h997a9dab34649aa0E
00001120 00000070 r _ZN84_$LT$atmega328p_hal..spi..Spi$u20$as$u20$embedded_hal..spi..FullDuplex$LT$u8$GT$$GT$4send17hfd5c80352a5cc8d5E
0000000c 00000252 r _ZN5w550020ActiveW5500$LT$E$GT$8write_to17h03ad5119f6a62654E
0000025e 00000258 r _ZN5w550020ActiveW5500$LT$E$GT$9read_from17h90d8084f962a2233E
000004b6 00000c6a R main

Based on some some searching, it sounds like the second column is the size of each object in hex. They sum up to ~4.5Kb The big things are w5500's write_to and read_from methods, and (assumedly) my program's main. Is it possible to explore the contents of those functions with this method to determine what their size is caused by?

[jonahbron]

Something I've found is that those two functions contain the only references to the dependency crate "BigEndian".

https://github.com/kellerkindt/w5500/blob/master/src/lib.rs#L247

It's possible that this dependency is too large. Will need to investigate further.

[jonahbron]

Apparently the ATMega328P has 32Kb of program memory. So it seems super weird that 4.5Kb would be too much...

[Rahix]

Hm. Try nm -u to see undefined symbols in that object file. You might also want try not unwrapping the result, because that will pull in core::fmt. Instead, you can .unwrap_or_else(|_| panic!());

[jonahbron]

@Rahix I made the unwrap change you suggested (and pushed up to the repo), and tried nm -u. It only had these items:

         U abort
         U __do_clear_bss
         U __do_copy_data
         U memset

Even if I add print-size, the output remains the same.

[Rahix]

Sorry, I really don't have the time right now to look into this in more detail ... I am pretty confident it has something to do with formatting of u64/i64/u128/i128. Whether that's code-size or some missing intrinsics in compiler-builtins I am not sure. You'll probably be best off if you try removing everything fmt related from that crate you are using. If that is not enough, look at panic related stuff. One other thing which might be relevant is enums with values, because they use a u64 as the discriminant internally. Good luck! Feel free to still post whatever you can dig up, maybe someone else has ideas ...

[jonahbron]

Thanks a lot for your input @Rahix . I'll start ripping the crate apart and see what I can get to compile.