Fix safe_packed_borrows error

japaric / stm32f103xx-hal

HAL for the STM32F103xx family of microcontrollers

Apache License 2.0

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Fix safe_packed_borrows error #32

Closed lnicola closed 6 years ago

lnicola commented 6 years ago

Fixes #31

japaric commented 6 years ago

Thanks for the PR. In this case I think it would be better just to remove the repr(packed) from the struct. It's not required for this to work; it was just used to work around a bug in rustc that misallocates statically allocated memory (rustc puts variables in .data, instead of in .bss and this wastes flash and makes initialization longer). None of this matter much in any case because the Buffer abstraction is going to be phased out in favor of safe &'static mut references.

Could you update the PR to drop the repr(packed) attribute?

lnicola commented 6 years ago

Done.

Not sure if it matters, but the a stripped release blinky binary was 66 Kb both before and after this change. I'm using openocd to flash it and it reports:

before:
wrote 2048 bytes from file target/thumbv7m-none-eabi/release/examples/blinky in 0.177486s (11.268 KiB/s)

after:
wrote 1024 bytes from file target/thumbv7m-none-eabi/release/examples/blinky in 0.099451s (10.055 KiB/s)

I'm not sure how relevant is this, or why there's such a large discrepancy between the ELF size and what openocd says.

japaric commented 6 years ago

was 66 Kb

Is that the output of ls? That's irrelevant to the actual flash usage. The proper binary size metric to measure is the output of the size command:

$ arm-none-eabi-size target/thumbv7m-none-eabi/release/examples/blinky
   text    data     bss     dec     hex filename
   1024       0       4    1028     404 target/thumbv7m-none-eabi/release/examples/blinky

text is Flash. bss + data is static RAM usage (excludes stack and heap usage).

Thanks for the update!

@homunkulus r+