MATLAB: How to force Polyspace to ignore null pointer

Polyspace Client for C/C++

I am using a (UINT8)* 0x0 as an absolute address but Polyspace errors out on this due to null pointer representation.

Best Answer

Polyspace cannot differentiate Null pointer from Absolute adressing.

Note that, this case is referenced at page 315 in the documentation (8.2.20.1.2. The NULL pointer case). In such cases, PolySpace cannot do the difference between the NULL pointer and the absolute address which could become at address 0x0.

Intrusive way proposed with PolySpace directive flag is valid.

#ifdef PolySpace
ComputedCRC = crc32((UINT8 *)0x1000, length, 0xFFFFFFFF);
#else
ComputedCRC = crc32((UINT8 *)0, length, 0xFFFFFFFF);
#endif

The only non intrusive way is to use option -post-preprocessing-command with a script which looks like the one attached (null_addr.pl). It works with the attached example (null.c) and replaces (UINT8 *)0 by (UINT8 *)0x1.

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MATLAB: How to avoid compilation error: expression must be a modifiable lvalue

(u8 *) dest is a temporary variable, which cannot be increased. Perhaps you want this:

*((u08*)dest++) = *((u08*)source++);

But this copies the first byte only. Perhaps memcpy would be smarter?

Or:

u08 *d = (u08 *) dest, *s = (u08 *) source;
while (count--) {
  *d++ = *s++;
}

MATLAB: Polyspace 2015a orange check IDP (Illegally dereferenced pointer)

Hi !

You can see this message for example when a memory buffer is allocated by malloc then used as an array but without checking if the malloc operation was ok. Example:

 uint8 * my_tab;
 my_tab = (uint8 *)malloc(100);
 data = my_tab[10];

Here my_tab is used as an array but the malloc operation has not been checked for a potential failure. So it "may not be allocated memory". In this situation, when accessing my_tab, you will see this message.

Please note that this message disappears if the pointer is tested for nullity before being accessed:

 uint8 * my_tab;
 my_tab = (uint8 *)malloc(100);
 if (my_tab != NULL)
  data = my_tab[10];

For your specific example, I'm not able to reproduce this message with this reproduction code:

 uint8 const * NvM_sectionPointer[( ( 4 ) )];
 volatile uint8 DrvEep_PolyspaceNvmStartAddress[( 1024 )*( 4 )];
 void f() {
  uint8 data;
  
  NvM_sectionPointer[0] = &DrvEep_PolyspaceNvmStartAddress[0];
  NvM_sectionPointer[1] = &DrvEep_PolyspaceNvmStartAddress[1024];
  NvM_sectionPointer[2] = &DrvEep_PolyspaceNvmStartAddress[2048];
  NvM_sectionPointer[3] = &DrvEep_PolyspaceNvmStartAddress[3072];
  data = NvM_sectionPointer[1][27];
 }

There is no allocation here so no reason to see this message. But I guess that your code is more complex and there are probably more write accesses to NvM_sectionPointer than in this example.

NvM_sectionPointer is probably a global array so in order to better understand why polypace gives this message, it may be interesting to see how it is accessed by using the Variable Access view : each write and read access to any global variable is displayed in this view so you can precisely trace the accesses of global variables.

Alex

Best Answer

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MATLAB: How to avoid compilation error: expression must be a modifiable lvalue

MATLAB: Polyspace 2015a orange check IDP (Illegally dereferenced pointer)

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