CODEWITHSUNDEEP
c++variablespointerslocalinitialization
blitzeus
blitzeus

Reputation: 495

uninitialized local variable

This code compiles and runs though gives a Microsoft compiler error that I cant fix

warning C4700: uninitialized local variable '' used.

This is in the last line of the code, I think

#include <iostream>
using namespace std;

const int DIM0 = 2, DIM1 = 3, DIM2 = 4, DIM3 = 5;

void TestDeclar();

int main(){
    TestDeclar();
    cout << "Done!\n";
    return 0;
}

void TestDeclar(){        
    //24 - array of 5 floats
    float xa[DIM3], xb[DIM3], xc[DIM3], xd[DIM3], xe[DIM3], xf[DIM3];
    float xg[DIM3], xh[DIM3], xi[DIM3], xj[DIM3], xk[DIM3], xl[DIM3];   
    float xm[DIM3], xn[DIM3], xo[DIM3], xp[DIM3], xq[DIM3], xr[DIM3];
    float xs[DIM3], xt[DIM3], xu[DIM3], xv[DIM3], xw[DIM3], xx[DIM3];

    //6  - array of 4 pointers to floats
    float *ya[DIM2] = {xa, xb, xc, xd}, *yb[DIM2] = {xe, xf, xg, xh};   
    float *yc[DIM2] = {xi, xj, xk, xl}, *yd[DIM2] = {xm, xn, xo, xp};
    float *ye[DIM2] = {xq, xr, xs, xt}, *yf[DIM2] = {xu, xv, xw, xx};

    //2 - array of 3 pointers to pointers of floats
    float **za[DIM1] = {ya, yb, yc};    
    float **zb[DIM1] = {yd, ye, yf};

    //array of 2 pointers to pointers to pointers of floats
    float ***ptr[DIM0] = {za, zb};   
    cout << &***ptr[DIM0] << '\n';  
}

Upvotes: 1

Views: 2868

Answers (2)

Ryan
Ryan

Reputation: 2404

You're accessing past the end of the ptr4D. DIM0 is 2, one greater than the last index of 1!

Change the last few lines to:

//array of 2 pointers to pointers to pointers of floats
float ***ptr4D[DIM0] = {za, zb};   
cout << &***ptr4D[0] << '\n';

Upvotes: 3

Daniel Noguchi
Daniel Noguchi

Reputation: 613

Not sure if I can help you but I tried to find out what's wrong trying to run it on my linux machine. I've compiled it on a ubuntu machine to compare and it went ok, even tellign the compiler to turn on all option warnings (passing the -Wall option). When running, I got this:

# Compiled it with -Wall to enable all warning flags and -g3 to produce extra debug information
~$ g++ -Wall stackoverflow.cpp -g3
./a.out 
Segmentation fault (core dumped)

Then I've tried to debug it with GDB (GNU debugger) and got this:

(gdb) r
Starting program: /home/ubuntu/a.out 

Program received signal SIGSEGV, Segmentation fault.
0x0000000000400986 in TestDeclar () at stackoverflow.cpp:34
34          cout << &***ptr4D[DIM0] << '\n';  
(gdb) s

So it appears that the problem is at the cout line. Checking your code again, DIM0's value is 2, so you're trying to access a memory address beyond the ptr4D. As user1721424 mentioned, just replace the DIM0 with 0 and it's done!

#After fixing it:
~$ ./a.out 
0x7fff74cd3830
Done!

Hope it helps!

Upvotes: 0

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