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VC crashes in 'Start without debugging' mode

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I usually run w/o debugging, but now the program only seems to run in debugging mode. My code stores large arrays and vectors (the vectors of which I've been hoping to 'delete' since I only need them temporarily, but closest I can get is 'clear'), which are used to store a mesh and its AABB tree. I use an .obj loader which was written in C along with the code I'm trying to run written in C++ (shouldn't pose a problem?). I'd thought the program was crashing because of a memory shortage, but it runs fine in debugging mode. Checked for leaks too, none found. Also, when I use 'printf' to try to find out where the problem lies, it runs without crashing. Any of this info raise any red flags?

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This would be a good time to investigate as to what running in debug mode actually does. I cannot say for certain, but a big offender is uninitialised variables. In debug mode all variables are initialised (usually with particular bit patterns that have meaning). It just might happen that the bit pattern one of your variables is set to works, but when your run without the debugger there no longer is that pattern.

Mixing C and C++ typically works fine. There are subtle differences sometimes but these are relatively rare in practise.

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Thanks for the quick reply.
The biggest puzzler for me is why a 'printf' statement would allow the program to run fine. I've checked all my variables and they seem to be initialized, else a warning would have come up anyway. Any links to what the debug mode does differently?

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Quote:
Original post by Demolit
I've checked all my variables and they seem to be initialized, else a warning would have come up anyway.
Not necessarily. A compiler can not prove that a variable is initialised before it is used, in every case. So unless it gives you false positives it wont necessarily be giving a warning in every case.

Anyway, the only two possibilities I've ever heard of are uninitialised variables, and different paths leading to files not being found. Check the results of attempts to open files.

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It seems to be the latter of what iMalc mentioned, but I'm not sure what to do about it. fclose seems to be messing up the memory, arrays created after it don't get initialized. Should I just not close the file? I'm definitely not accessing the file again after closing it, it's merely in a function which opens a file and reads the data into a struct.
And as usual, calling 'printf' or 'fprintf(stderr)', or even std::cout, before opening the second file allows the program to run without problems. A stream buffer problem?

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Something else, since no one seemed to mention it, that would be worth looking into is the compiler settings itself. When you mess with the linker settings in visual studio (for instance, to change between multithreaded and single threaded libraries) it only effects the current build specifications (unless changed manually to both). by default, in VS at least, you are only changing the settings to the debug build.

There are many many many painful and strange conflicts that can happen when mixing single and multithreaded libraries.

In addition, optimizing compilers sometimes perform certain things like struct alignment that can sometimes cause problems. so you could always mess around with the optimizations, lowering them until it works (if that helps anyways), and then using information about what differenciates that particular optimization technique.

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I'm afraid I don't mess with the configurations enough to know how those are configured.
These look to be my configurations:
C/C++ optimization is disabled, Linker optimization is default.
Runtime library is multi-threaded debug (no option for single threaded)

Following what you've mentioned, I don't think changing these will affect the outcome.

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PaulCesar's suggestions might not explain your problem in this case. Assuming of course my interpretation of your description is correct in that it works when you run a debug build normally, but then without recompiling the same debug build subsequently fails to run without the debugger.

Double-check what is passed to fclose is exactly what was obtained from fopen.
Any chance you can post a section of code around where you think the problem is? In particular I'd like to confirm what your description of arrays created after the fclose, that are not being initialised, refers to. Is the file opened in the same function that it is closed from? If so, perhaps posting the whole function would be best, if that is okay.

Oh and of course I just thought I should check that you've tried a rebuild-all[smile].

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Quote:
Assuming of course my interpretation of your description is correct in that it works when you run a debug build normally, but then without recompiling the same debug build subsequently fails to run without the debugger.

Yes, but even if I recompile it, it still fails without debugger.

Yes I always rebuild-all. Tried a clean then rebuilding, didn't change anything.

Did a few more tests, the problem occurs after using the conversion function.


// This is probably the problem, works fine when I don't use it
template <typename T>
vector<T> convertArrayToVector(T *array, int size)
{
vector<T> newVec;
for(int i=0; i<size; i++)
{
newVec.push_back(array);
}
return newVec;
}

// This function works fine, tested and used several times
// If I chuck a random 'printf' statement here, program runs fine
mesh_t *mesh_load(const char *obj_filename)
{
mesh_t *mesh = mesh_create();
char buf[MAX_LINE_LENGTH];
const char *bufp;
size_t token_len;
int line_number = 0;
const material_t *current_material;
char material_filename[MAX_LINE_LENGTH];
char material_path[MAX_PATH_SIZE];
FILE *file = fopen(obj_filename, "r");
int i;

if(!file)
return NULL;

/* Get the relative path where the mtl file is (it should be in the same
location as the obj file) */

strcpy(material_path, obj_filename);
for(i = (int)strlen(obj_filename); material_path != '\\' &&
material_path != '/' && i >= 0; i--)
{
material_path = '\0';
}

/* Process each line from the OBJ file */
while (fgets(buf, sizeof(buf), file))
{
... // Process object file
}

/* Pad the normals and tex coords arrays to be as large as the vertex
* array. */

pad_vertex_data(&mesh->normals, mesh->vertices.n_vertices);
pad_vertex_data(&mesh->tex_coords, mesh->vertices.n_vertices);

fclose(file); // Had been giving problems
return mesh;
}

int main(int argc, char **argv)
{
... (opengl and glut initialization)

ship.mesh = mesh_load(argv[2]);
vector<triangle_t> ship_tri = convertArrayToVector(
ship.mesh->triangles, ship.mesh->n_triangles);

asteroid.g_mesh = mesh_load(argv[1]);
cout << asteroid.mesh->vertices.vertices[0].x << endl; // Crashes here, doesn't seem to be initialized

glutMainLoop();

return EXIT_SUCCESS;
}

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Set a break point at the line

cout << asteroid.mesh->vertices.vertices[0].x << endl; // Crashes here, doesn't seem to be initialized

and run it in the debugger. When the break point is hit, hover your mouse over the variables and make sure they are all valid. If they are invalid, then you need to find where in your code you fail to give them valid values. Make sure the array passed to convertArrayToVector really is of length size. Also make sure that the parameters you are giving it when you call it (ship.mesh->triangles and ship.mesh->n_triangles) are valid.

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