BSP MEM POSIX realloc impl NULL input ptr handling, diff. vs. C standard

[atigyi]

The SDK BSP MEM's realloc implementation does not enforce C standard behaviour. This is required if the underlying platform's realloc function doesn't meet the standard. In this particular case the behaviour on NULL input ptr value differs from the standard (below) for Raspberry Pi / ARM architecture.

iot-device-sdk's POSIX realloc function impl.

realloc - memory reallocator : "If ptr is a null pointer, realloc() shall be equivalent to malloc() for the specified size."
C realloc C standard definition.

Some more details

• Seems "only" the Wolfssl uses realloc and/or uses 'realloc' with NULL ptr input.
• The SDK actually propagates the standard C adherence to the underlying platform's realloc function by only forwarding the parameters intact, without applying any logic.

[sridharan-8888]

Additional info on the issue, it seems to be related to 'memory_limitter'

• Device: Raspberry PI
• OS : Raspien/Raspberry PI OS
  With the 'memory_limitter' debug extension
  Code causing the issue:
  https://github.com/GoogleCloudPlatform/iot-device-sdk-embedded-c/blob/master/src/libiotc/debug_extensions/memory_limiter/iotc_memory_limiter.c#L230-L232

[atigyi]

Indeed, this isn't C standard compatible. Did you conduct tests with if-null-return-null lines removed?