STM32 compilation warning issues

[jeromecoutant]

Description

This PR follow @pauluap work in #6262
and correct ("only") compilation warning in the ST driver files.

Internal tickets has been raised in ST side to align code.

Thx

Pull request type

[x] Fix
[ ] Refactor
[ ] New target
[ ] Feature
[ ] Breaking change

[pauluap]

I have compiler messages covering this set of changes

https://github.com/pauluap/mbed-os/tree/compiler_warning_declaration_not_provided

../targets/TARGET_STM/stm_spi_api.c: In function 'spi_master_start_asynch_transfer':
../targets/TARGET_STM/stm_spi_api.c:531:5: warning: implicit declaration of function 'HAL_SPIEx_FlushRxFifo' [-Wimplicit-function-declaration]
     HAL_SPIEx_FlushRxFifo(handle);
     ^~~~~~~~~~~~~~~~~~~~~

https://github.com/pauluap/mbed-os/commits/compiler_warning_inline_keyword_misuse

Compile: serial_device.c
../targets/TARGET_STM/TARGET_STM32F7/serial_device.c:42:15: warning: inline function 'get_uart_index' declared but never defined
 inline int8_t get_uart_index(UARTName uart_name);
               ^~~~~~~~~~~~~~

https://github.com/pauluap/mbed-os/commits/compiler_warning_strict_antialiasing
This warning appears at the -O3 optimization level

Compile: stm32f7xx_hal_crc.c
../targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_hal_crc.c: In function 'CRC_Handle_8':
../targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_hal_crc.c:436:8: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
        *(__IO uint16_t*) (&hcrc->Instance->DR) = (uint16_t)((uint16_t)((uint16_t)(pBuffer[4*i])<<8) | (uint16_t)(pBuffer[4*i+1]));
        ^
../targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_hal_crc.c:440:8: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
        *(__IO uint16_t*) (&hcrc->Instance->DR) = (uint16_t)((uint16_t)((uint16_t)(pBuffer[4*i])<<8) | (uint16_t)(pBuffer[4*i+1]));
        ^
../targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_hal_crc.c: In function 'CRC_Handle_16':
../targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_hal_crc.c:470:6: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
      *(__IO uint16_t*) (&hcrc->Instance->DR) = pBuffer[2*i];
      ^

Compile: stm_spi_api.c
In file included from .././targets/TARGET_STM/TARGET_STM32F7/spi_device.h:33:0,
                 from ../targets/TARGET_STM/stm_spi_api.c:42:
.././targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_ll_spi.h: In function 'LL_SPI_TransmitData16':
.././targets/TARGET_STM/TARGET_STM32F7/device/stm32f7xx_ll_spi.h:1388:3: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
   *((__IO uint16_t *)&SPIx->DR) = TxData;
   ^

[pauluap]

I currently think that this function needs further work to handle other potential negative number issues. I've generated a pull request for this particular set of changes - #6609

[jeromecoutant]

PCD warnings are now followed by #6609
I removed then this part from this PR

[0xc0170]

@pauluap Please rereview

[pauluap]

Ok, I checked out the PCD comments and I now agree with the ST driver team that my more extensive changes aren't required. I'll clean up #6609 to get things back in line with the ilen variant.

[0xc0170]

what is this solving for GCC?

[pauluap]

pauluap@27425bc

The warning messages that this change clears is shown in the commit message. The warning only appears at the -O3 optimization level

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 1743
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/6599/

Triggering tests

/morph test
/morph uvisor-test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 1377
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/6599/

[mbed-ci]

Test : SUCCESS

Build number : 1546
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/6599/1546