Pfthb

I found the below warning in map file , the struct extern declaration TYPE got changed in file2.c declaration. Below warning from IAR compiler,
Please let me know what is the impact of below type cast.
what is the memory size in file2.c while link time ?

I am trying to find impacts of this implementation not the solution

"struct_tag" to "uint8"

Warning[w6]: Type conflict for external/entry "Block_01", in module file2.c against external/entry in module file1.c; different basic types 
 /* In module file2.c: */
 uint8 NvM_Block_01;
 typedef unsigned char uint8;
 /* In module file1.c: */
 Block_01_T Block_01;
typedef struct Block_01_Tag Block_01_T;

typedef struct Block_01_Tag

/* 4 bytes with CRC16 */

 uint16 Data_01;
 uint16 Crc_01;
Block_01_T;

File1.c

Block_01_T Block_01 = 1234,1;

File2.c

extern unsigned char Block_01;
#define RPM_BLOCK (&Block_01)

Thanks
Damodaran

In file2.c, Block_01 is given type unsigned char, which is 1 byte in size. This will access the first byte of the structure Block_01_t, which will be part of Block_01_T.Data_01.

You have two variables of the same name. Block_01 and different types. This is not allowed. You need to change one of them.

Block_01_T Block_01 = 1234,1; // in File1.c
extern unsigned char Block_01; // in File2.c

If you want both files to refer to the same variable, you can use.

extern Block_01_T Block_01; // in File2.c

The linker generally doesn't care about the size of object, just their addresses. The compiler reserves space in the object file that defines the object. In this case, the definition is in File1.c, which declares a structure containing two uint16, so it will most reserve at least 4 bytes.

According to the C standard, the consequences are undefined when you use Block_01 in File2.. But I think it's likely that it will be equivalent to giving it the same structure type declaration, and then using *(char *)(&Block_01).