SIMPLELINK-CC13XX-CC26XX-SDK: HardFault caused by misaligned pointer in bdb_reporting.c

With SimpleLink CC13XX/CC26XX SDK Version 7.10.01.24, attribute reporting for float (ZCL_DATATYPE_SINGLE_PREC) attributes fails with a HardFault due to a misaligned pointer access on line 1895 in bdb_reporting.c:

      float L = *((float*)lastValue);
      float D = *((float*)delta);
      float C = *((float*)curValue);

With -O0 this works, but with -Oz the FPU instruction loading the (misaligned) float causes a HardFault.

The pointers lastValue, delta, and curValue are of type uint8_t*, and at least lastValue and curValue are not properly aligned (address divisible by 4) for a float pointer. Dereferencing misaligned pointers causes undefined behaviour in C, so a HardFault is a perfectly valid result here.

The same thing probably happens for other attribute types with _Alignof larger than 2, but I haven't tested that.

I worked around the issue by using a defensive memcpy for all three values:

      uint8_t len = zclGetDataTypeLength( datatype );
      float L, D, C;
      OsalPort_memcpy( &L, lastValue, len );
      OsalPort_memcpy( &D, delta, len );
      OsalPort_memcpy( &C, curValue, len );

That should probably be fixed in the SDK.