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Code Prover warning 'Illegally dereferenced pointer'

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Nideesh Madhu
Nideesh Madhu on 5 May 2021
Commented: Anirban on 6 May 2021
While running the code prover i got same Orange warning on many places in the code. For example in the function,
void DD_XYZ_Init( uint32_t addr_mcs_crit_ctrl )
( ( *((uint32_t volatile *)((uint32_t)addr_tim_crit_ctrl + ( (uint32_t)((uint32_t)0xf0100000+0x00001024) - (uint32_t)((uint32_t)0xf0100000+0x00001024) ))) ) ) = 0;
The Warning that i got,
Illegally dereferenced pointer
Warning: pointer may be outside its bounds
Dereference of expression (pointer to volatile unsigned int 32, size: 32 bits):
Pointer may be null.
Points to 4 bytes at unknown offset in buffer of unknown size, so may be outside bounds.
Pointer may point to dynamically allocated memory.
My Question,
We have given proper range for ‘addr_tim_crit_ctrl’ in constraint specification file, but still getting the warning. What could be the reason?
Nideesh Madhu
Nideesh Madhu on 5 May 2021 is a typo.. Function parameter is addr_tim_crit_ctrl and the range I have given is 0×F0130012 - 0×F0130014

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Accepted Answer

Anirban on 6 May 2021
Edited: Anirban on 6 May 2021
In your example, you are converting an integer to a pointer. These conversions have results that are implementation-dependent and in the most general case, the pointer might point to an address that is illegal to dereference. That is why Code Prover is showing an orange check.
Even if you constrain the integer to a range of addresses, since Code Prover has no knowledge of the size of your target and the memory layout, this constraint is not sufficient to determine that the addresses are valid and the dereference is ok.
If you are sure that the dereference is ok, you can justify this orange check. See Address Polyspace Results Through Bug Fixes or Justifications.
Anirban on 6 May 2021
As of now, there is no way to specify a memory layout. The most you can do is specify the sizes of fundamental data types, alignment, endianness and so on using the option Target processor type. If you contact MathWorks Technical Support, they might provide you specific solutions for your needs.

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