CODEWITHSUNDEEP
c++
DeepSpace
DeepSpace

Reputation: 81654

Run time error while using realloc: " _CrtIsValidHeapPointer(pUserData), dbgheap.c"

The following code is written in C++ but using realloc from stdlib.h because I don't know much about std::vector.

Anyway, I get this weird run time error " " _CrtIsValidHeapPointer(pUserData), dbgheap.c".

If you would like to see the whole method or code please let me know.

I have 2 classes, Student and Grades. Student contains 

char _name[21];         
char _id[6];             

int _numOfGrades;
int* _grades;
float _avg;

and Grade simply contains 

Student* _students;
int _numOfStudents;

while the following works

_grades = (int *)realloc(_grades,(sizeof(int)*(_numOfGrades+1)));

this will create that weird run time error:

_students = (Student *)realloc(_students,(sizeof(Student)*(_numOfStudents+1)));

Both _grades and _students are created with new with no problem at all. The problem is only while trying to realloc _students.

Any input will be welcome.

Upvotes: 2

Views: 2080

Answers (1)

Adam Rosenfield
Adam Rosenfield

Reputation: 400454

You cannot mix allocators—if you allocate memory with operator new[], you must deallocate it with operator delete[]. You cannot use free(), realloc(), or any other memory allocator (e.g. Windows' GlobalFree()/LocalFree()/HeapFree() functions).

realloc() can only reallocate memory regions which were allocated with the malloc() family of functions (malloc(), calloc(), and realloc()). Attempting to realloc any other memory block is undefined behavior—in this case, you got lucky and the C runtime was able to catch your error, but if you were unlucky, you might silently corrupt memory and then later crash at some random point in an "impossible" state.

Upvotes: 1

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