为什么会出现错误：从类型'UINT8 *'分配给类型'P_Name_t'时类型不兼容

Question

I don't understand why I am getting the error above and how to fix it. Please help.

//STRUCTURES
typedef UINT8 P_Name_t[5];
typedef UINT8 ChipSN_t[3]; 

typedef struct                   
{  
   ChipSN_t  ChipSN; 
   <other members>   
} ChipIdent_t;


typedef struct Data_t              
{ 
   ChipIdent_t      ReadOnlyMemID;
    <other members>   
} Data_t;


typedef struct                
{
   P_Name_t NameOfPart;   
   <other members>
} Log_t;

Data_t     Data_Src;

typedef struct
{
   P_Name_t       NameOfPart;           
   ChipSN_t       ChipSN;   
}PartNum_ID_t;


//VARIABLE DECALARTION
PRIVATE PartNum_ID_t PN_ChipID[12]; 
PRIVATE Log_t   *LogEntry = NULL;               


//Usage in code
PN_ChipID[0].NameOfPart = LogEntry->NameOfPart; 
PN_ChipID[0].ChipSN = Data_Src.ReadOnlyMemID.ChipSN;

I don't understand why I get the error. The LogEntry->NameOfPart is of type P_Name_t and PN_ChipID[0].NameOfPart is of the same type. I don't know if I am missing something here. Please explain.

Answer 1

Apart from hiding it behind complicated structs and pointers,
you are basically trying to do this:

#include <string.h>

int main(void)
{
    char a[5];
    char b[5]={'a', 'b', 'c', 'd', 'e'};

    // version 1 works
    memcpy(a, b, sizeof(b)); // assuming that a and b are same size.

    // version 2 gives the same error as you quote
    //a=b;

    return 0;    
}

It gives the same error. While array identifiers used as R-values decay to pointers, you cannot "write to the pointer" representing an array as L-value.

Besides, what do you want to achieve? What you anyway need to do is to copy the content of one array to the other. Use memcpy() or any other method to do that.

Answer 2

 incompatible types when assigning to type 'P_Name_t' [...] 

[...] why i get the error[?] The LogEntry->NameOfPart is of type P_Name_t and PN_ChipID[0].NameOfPart is of the same type.

P_Name_t is an array, namely of 5 unit8_t .

PN_ChipID[0].NameOfPart is of type P_Name_t .

So this line

PN_ChipID[0].NameOfPart = LogEntry->NameOfPart;

tries to assign to an array, namely to PN_ChipID[0].NameOfPart .

In C it is not possible to assign to an array, hence the error during compilation of the above line.

Answer 3

For the benefit of this thread and future answer seekers. LogEntry->NameOfPart is an array of 5 elements, namely:

LogEntry->NameOfPart[0]
LogEntry->NameOfPart[1] 
LogEntry->NameOfPart[2] 
LogEntry->NameOfPart[3]
LogEntry->NameOfPart[4]

and

PN_ChipID[0].NameOfPart is similar

PN_ChipID[0].NameOfPart[0] 
PN_ChipID[0].NameOfPart[1]
PN_ChipID[0].NameOfPart[2]
PN_ChipID[0].NameOfPart[3]
PN_ChipID[0].NameOfPart[4]

So the way to copy this is to run it through a loop copying element by element

for i=....
{
  PN_ChipID[0].NameOfPart[i] = LogEntry->NameOfPart[i];
}