how to pass a value to the bitfield-CodePudding

I don't know how to pass a value to the bitfield:

in header file I have the struct definition below:

typedef struct { boolean Error; } Struct_A_T;

Struct_A_T Struct_A = {0U};
boolean WriteValue;

if (TRUE) {
  Struct_A.Error.index = WriteValue;
}
}
else {
  index  ;
}

As you can see, the index will increment, I want the WriteValue to pass a value to the bit location equal to index for Struct_A_Error. I don't know how should I define this and make the bit as flexible so index can control the bit location. Thanks

expect to have bit location update to the value of index

CodePudding user response：

expect to have bit location update to the value of index

That's not how bitfields work. That's impossible in C.

Types in C are static. They can't be changed at runtime – so your bitfield must always be in the same position.

If you need to set a specific bit in a memory location, you will have to put an integer there, and use bit shifts and logical operators to put the bit where you want it.

CodePudding user response：

As I see it, OP does not want a bit-field or bool struct member, yet a simply unsigned.

#include <stdbool.h>

typedef struct {
  unsigned Error;
} Struct_A_T;

Struct_A_T Struct_A = {0U};

...
bool WriteValue;
...
if (TRUE) {
  unsigned mask = 1u << index; 
  if (WriteValue) Struct_A |= mask;
  else Struct_A &= ~mask;
}
...

index should be less than an unsigned bit-width (typically 32).