Heap corruption - Loading file (StaticMesh) - c++

Question

I have the following class declared:
class StaticMesh
{
public:
unsigned int v_count;
float* vertices;
unsigned int n_count;
float* normals;
void Load_lin(const char* file);
void Draw(void);
void Release(void);
};
This class (as it's name indicates) represents a static mesh, which can load .lin files.
.lin files are generated by another application I made using C#. This application reads .obj files and generates the .lin file that has this structure:
v_count v
n_count n
a#a#a
b#b#b
a#a#a
b#b#b
Where v is the number of vertices, n the number of normals, and a/b represent coordinates.
Load_lin(const char*) is the function that loads these files, and here it is:
void StaticMesh::Load_lin(const char* file)
{
std::ifstream in (file);
if (!in)
{
std::cout << "Error: Failed to load staticmesh from '" << file << "'." << std::endl;
return;
}
char buffer[256];
in.getline(buffer, 256);
sscanf_s(buffer, "v_count %i", &v_count);
in.getline(buffer, 256);
sscanf_s(buffer, "n_count %i", &n_count);
vertices = new float[v_count];
normals = new float[n_count];
unsigned int a = 0;
unsigned int p = 0;
float x, y, z;
do
{
in.getline(buffer, 256);
if (buffer[0] == '\n' || buffer[0] == '\r') break;
sscanf_s(buffer, "%f#%f#%f", &x, &y, &z);
vertices[a++] = x;
vertices[a++] = z;
vertices[a++] = y;
in.getline(buffer, 256);
sscanf_s(buffer, "%f#%f#%f", &x, &y, &z);
normals[p++] = x;
normals[p++] = z;
normals[p++] = y;
} while (!in.eof());
in.close();
}
I've narrowed down the cause of the error to this function, however, the error only shows when the application is closed, and sometimes it doesn't happen.
So the line where the error occurs is actually the end of WinMain:
return msn.message;
I've went further and used std::cout to print the variables 'a' and 'p', this causes an heap corruption error, but this time in malloc.c line 55:
__forceinline void * __cdecl _heap_alloc (size_t size)
{
if (_crtheap == 0) {
_FF_MSGBANNER(); /* write run-time error banner */
_NMSG_WRITE(_RT_CRT_NOTINIT); /* write message */
__crtExitProcess(255); /* normally _exit(255) */
}
return HeapAlloc(_crtheap, 0, size ? size : 1);
} // LINE 55
I've searched for this last error with no avail.
Thank you for your time. :)

Answer 1

I think v_count and n_count mentions the number of vertices. According to the code, each vertex will have 3 components (x/y/z) and each component is stored in a float variable. This means that you need to allocate 3 times v_count and 3 times n_count number of floats for vertices and normals respectively.
i.e modify your allocation as
vertices = new float[v_count * 3];
normals = new float[n_count * 3];

Answer 2

v_count v means the number you read is (unsigned int)'v'. And then you have vertices = new float[v_count];. It's likely you don't allocate enough storage and write outside the bounds of the arrays vertices and normals resulting in undefined behavior.

Answer 3

Just try re-write your code to use std::vector instead of raw pointers. This will really help you avoid issues with heap corruption.