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Access Violation Using memcpy or Assignment to an Array in a Struct


Access Violation Using memcpy or Assignment to an Array in a Struct

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Access Violation Using memcpy or Assignment to an Array in a Struct
Tag : cpp , By : user157138
Date : January 02 2021, 06:48 AM


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Struct assignment or memcpy?


Tag : c , By : David
Date : March 29 2020, 07:55 AM
This might help you The struct1=struct2; notation is not only more concise, but also shorter and leaves more optimization opportunities to the compiler. The semantic meaning of = is an assignment, while memcpy just copies memory. That's a huge difference in readability as well, although memcpy does the same in this case.
Use =.

array assignment access violation


Tag : cpp , By : Santhanam
Date : March 29 2020, 07:55 AM
may help you . I don't see how it can ever work. You allocate one byte on the heap but treat it as multiple bytes:
byte *Packet1 = new byte;
*Packet1 = 0x01;
*(Packet1+1) = 'P';  // !!!
*(Packet1+2) = '1';  // !!!
*(Packet1+3) = STX;  // !!!
*(Packet1+4) = '(';  // !!!

Memcpy or struct assignment?


Tag : c , By : Thomas Plunkett
Date : March 29 2020, 07:55 AM
like below fixes the issue I don't think that this can be called struct assignment. You are assigning to the individual fields.
struct assingment in your case where you are merely interested in initialization of the object on the stack that you are "reserving" could use a temporary:
struct base tmp = {
       .type = 1,
       .prev = NULL,
       // whatever other fields you want to initialize
};
var->base = tmp;
var->base = (struct base){
       .type = 1,
       .prev = NULL,
       // whatever other fields you want to initialize
};

Access violation when trying to populate an array of struct


Tag : c , By : Bobblegate
Date : March 29 2020, 07:55 AM
it fixes the issue as it happens and as i am new to pointers i have not realize that when debugging i will not see the elements of given pointer to an array as i am used to with normal Array[] but looping through result which i did not even try as when i was hovering above the Array* within the while loop expecting to see the elements as in a normal array:
Data[] DataArr = new Data[1000] <- i have expected to actually see the body of the array while looping and populating the Data* and did not realize it is not an actual array but a pointer to one so you can not see the elements/body.
void dodata(int requestedMasterArrLength,int requestedStringSize){

    int ccountr,count;
    count=0;
    UntArr=NULL;
    UntArr = (Unit *)malloc(sizeof(Unit)*requestedMasterArrLength);

        while(count!=requestedMasterArrLength)
        {
                char dummyStringDataObject[]= "abcdefgHi";

                UntArr[count].StrVal=NULL;  

                dummyStringDataObject[requestedStringSize-1] = count+'0';
                UntArr[count].Id= count;
                ccountr=0;
                UntArr[count].StrVal= (char*)malloc(sizeof(char)*requestedStringSize);
                    while(ccountr!=requestedStringSize){
                        UntArr[count].StrVal[ccountr] = dummyStringDataObject[ccountr];
                        ++ccountr;
                    }
            ++count;
        }


}

can a struct assignment overlap similar to memmove() or is struct assignment like memcpy()?


Tag : c , By : artifex
Date : March 29 2020, 07:55 AM
hope this fix your issue Section 6.5.16.1 ("Simple assignment") of the C standard (reading from draft N1548) states:
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