Error c4700 uninitialized local variable n used

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Learn more about: Compiler Warning (level 1 and level 4) C4700	Compiler Warning (level 1 and level 4) C4700	08/30/2022	C4700	C4700	2da0deb4-77dd-4b05-98d3-b78d74ac4ca7

uninitialized local variable ‘name‘ used

Remarks

The local variable name has been used, that is, read from, before it has been assigned a value. In C and C++, local variables aren’t initialized by default. Uninitialized variables can contain any value, and their use leads to undefined behavior. Warning C4700 almost always indicates a bug that can cause unpredictable results or crashes in your program.

To fix this issue, you can initialize local variables when they’re declared, or assign a value to them before they’re used. A function can be used to initialize a variable that’s passed as a reference parameter, or when its address is passed as a pointer parameter.

The /sdl (Enable Additional Security Checks) compiler option elevates this warning to an error.

Example

This sample generates C4700 when variables t, u, and v are used before they’re initialized, and shows the kind of garbage value that can result. Variables x, y, and z don’t cause the warning, because they’re initialized before use:

// c4700.cpp
// compile by using: cl /EHsc /W4 c4700.cpp
#include <iostream>

// function takes an int reference to initialize
void initialize(int& i)
{
    i = 21;
}

int main()
{
    int s, t, u, v;   // Danger, uninitialized variables

    s = t + u + v;    // C4700: t, u, v used before initialization
    std::cout << "Value in s: " << s << std::endl;

    int w, x;         // Danger, uninitialized variables
    initialize(x);    // fix: call function to init x before use
    int y{10};        // fix: initialize y, z when declared
    int z{11};        // This C++11 syntax is recommended over int z = 11;

    w = x + y + z;    // Okay, all values initialized before use
    std::cout << "Value in w: " << w << std::endl;
}

When this code is run, t, u, and v are uninitialized, and the output for s is unpredictable:

Value in s: 37816963
Value in w: 42

Дообрый день! Имеется следующий код

#include "stdafx.h"
#include <iostream>
#include <math.h>
#include <conio.h>

using namespace std;

double count(double, double, double, double);
void input(void);
void output(void);

int main()
{
	double a, b, c, d, y;

	input();
	y = count(a, b, c, d);
	output();

	double count (double a, double b, double c, double d) {
		return 2 * sqrt((sin(a) / fabs(tan(b - a)) + (log(c) / d)));
	}

	void input(void) {
		cout << "Enter a" << endl;
		cin >> a;
		cout << "Enter b" << endl;
		cin >> b;
		cout << "Enter c" << endl;
		cin >> c;
		cout << "Enter d" << endl;
		cin >> d;
	}

	void output(void) {
		cout << "Your y is " << y;
	}

	_getch();

	return 0;
}

При компиляции выскакивают ошибки:

Error C4700 uninitialized local variable ‘a’ used
Error C4700 uninitialized local variable ‘b’ used
Error C4700 uninitialized local variable ‘c’ used
Error C4700 uninitialized local variable ‘d’ used

Прдскажите, пожалуйста, в чем проблема.. не могу понять.. переменные же вроде инициализировала еще в самом начале функции main()

Error c4700 uninitialized local variable

My issue is i am getting error C4700: uninitialized local variable ‘response’ used on line 26. I know it’s probably something simple I’m completely missing please help.

Here’s my instructions:

The local Driver’s License Office has asked you to write a program which grades the written portion of the driver’s license exam. The exam has 20 multiple choice questions. The correct answers are:

1. A 2. D 3. B 4. B 5. C 6. B 7. A 8. B 9. C 10. D 11. A 12. C 13. D 14. B 15. D 16. C 17. C 18. A 19. D 20. B

In main, declare an array and initialize it with the above correct answers. Also declare a second array for an exam taker’s answers, and get a text file name from the user.

This program will have two functions:

1) have the user enter 20 answers from an exam taker and write the answers to the text file (validate that the answers are A, B, C, or D). See the 20 exam taker’s answers below.

Hint: open (and close) the file in the function.

2) read the text file of the exam taker’s answers and store them in the exam taker’s array, which was declared in main.

Then in main, the program should display the following information:

-whether the exam taker passed or failed (15 of the 20 answers must be correct).

-total number of questions answered correctly

-total number of questions answered incorrectly

-a list of the numbers of the questions answered incorrectly (question numbers are 1-20).

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Error c4700 uninitialized local variable

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Answered by:

Question

I created a infix to postfix converter. Below is the code:

// pstcnvrtr.cpp : Converts infix notation to postfix.
//Author: Evolution; Date: 9 Feb 2013 Time:9:17pm
#include
#include
using namespace std;
int priority(char );
void main()
<
char *stack,*symbol,*post,*temp;
int top=-1,len,psym,pstk;
cout top=top+1;
stack[top]='(‘;
stack[top+1]=’′;
>
else if(*symbol==’^’||*symbol==’/’||*symbol==’*’||*symbol==’+’||*symbol==’-‘)
<
psym=priority(*symbol);
pstk=priority(stack[top]);
while(psym <
*post=stack[top];
top—;
stack[top+1]=’′;
post++;
*post=’′;
pstk=priority(stack[top]);
>
top=top+1;
stack[top]=*symbol;
stack[top+1]=’′;
>
else if(*symbol==’)’)
<
while(stack[top]!='(‘)
<
*post=stack[top];
top—;
stack[top+1]=’′;
post++;
*post=’′;
>
top—;
stack[top+1]=’′;
>
else
<
*post=*symbol;
post++;
*post=’′;
>
symbol++;
>
post=temp;
cout

Answers

Also if I follow one of your methods and declare the arrays like this:

Then I meet a series of errors which makes the entire code to be modified. The errors are listed below:
Error 1 error C2106: ‘=’ : left operand must be l-value

Error 6 error C2106: ‘=’ : left operand must be l-value

Error 2 error C2105: ‘++’ needs l-value

Error 3 error C2105: ‘++’ needs l-value

Error 4 error C2105: ‘++’ needs l-value
Error 5 error C2105: ‘++’ needs l-value

You should probably change the code to something like:

Also, post needs to be initialized. I don’t understand this algorithm well enough to tell you how it needs to be initialized; it doesn’t make sense to me.

As a final comment, if you are going to program in C or C++, you need a basic understanding of pointers and arrays before you can move forward. It’s clear from your post that you are confused over these fundamental concepts.

This material is covered in every introductory C or C++ textbook. I suggest you re-read this material, or Google/Bing for «pointers arrays C» and a number of tutorials will pop up.

Look at this little snippet of code. You create a variable called stack. Stack is will point to memory that contains a sequence of chars. But you never told it where to point. You then decide to poke ‘(‘ at that (undefined) memory location. The compiler sees this and emits the warning you are seeing.

If this code worked for you under Turbo C, then it was simply a fluke that it did.

You need to provide storage for the memory that you are writing. There are a number of ways to do it. The most fundamental way (but not really recommended in modern C++) would be to use new to allocate a buffer, the delete to free it

Another option is to put it on the stack. This option is probably the simplest, and works well if you know in advance how large your buffers need to be and they are relatively small.

The more modern C++ way to tackle something like this would be:

I very clearly understand what the error is all about

The same fundamental programming error occurs with variables
«post» and «symbol»:

. // «symbol» never assigned a value

>gets_s(symbol,20); // storing at a random address

As «post» has never been assigned a value, you’re storing
a random value in «temp».

I tried assigning null string to all the undeclared strings as below:

This of course removed all the errors but created a run-time error and I have to abort the program. (

You should always give the *exact* error message.

Note that in versions of VC++ since 2003 when you define
a char string in that way it is placed in a «read-only»
area of memory and so the string *cannot* be changed later.
Any attempt to do so will cause a run-time error. So to
catch any such attempt to change the string at *compile*
time, you should declare it as a pointer to const char:

const char *stack=»″;

«String literals now have the type const char [] and are now
placed in a read-only section of memory. Changing that memory
will now cause an access violation.»

Of course, in this case each pointer holds the address of
a zero-length string so it would be impossible to copy a
longer string to that address without causing a memory
overwrite even if they weren’t in a read-only area.

Further, string literals are not STRINGS. They are arrays of const char.

In your case above you have a bunch of 2 character arrays. Even if you were allowed to store into them, you’d overfill them with things like gets_s(symbol, 20) as it’s only 2 char’s long.

This is C++ ditch the horrendous C stdio library, it’s lack of a string type, and your non-comprehension of memory allocation and write in C++ using the std::string class and iostream classes.

Thanks for the reply.

I understand what you are trying to explain but what if I REALLY want to store these random values only. as during the correct phase of time I am assigning them the value what I want to assign.

So isn’t there a way that will not consider assigning theses random value to a variable as an error.

This is the question I want answer for?

Thanks a lot for helping me.

But just clear me one more thing. The methods you are describing me are those which contains a fix size for the array. What if I don’t want this size boundation.

I mean is there a way to point to memory that will contain a sequence of chars plus I don’t need to declare the size also as it is not already known what will be the size plus I don’t want to assign any values in the starting as I want it to be entered when I will be requiring the need for it.

Also if I follow one of your methods and declare the arrays like this:

Then I meet a series of errors which makes the entire code to be modified. The errors are listed below:
Error 1 error C2106: ‘=’ : left operand must be l-value

Error 6 error C2106: ‘=’ : left operand must be l-value

Error 2 error C2105: ‘++’ needs l-value

Error 3 error C2105: ‘++’ needs l-value

Error 4 error C2105: ‘++’ needs l-value
Error 5 error C2105: ‘++’ needs l-value

Please guide me what I should do in this situation.

Any reply would be really appreciated. )

Also if I follow one of your methods and declare the arrays like this:

Then I meet a series of errors which makes the entire code to be modified. The errors are listed below:
Error 1 error C2106: ‘=’ : left operand must be l-value

Error 6 error C2106: ‘=’ : left operand must be l-value

Error 2 error C2105: ‘++’ needs l-value

Error 3 error C2105: ‘++’ needs l-value

Error 4 error C2105: ‘++’ needs l-value
Error 5 error C2105: ‘++’ needs l-value

You should probably change the code to something like:

Also, post needs to be initialized. I don’t understand this algorithm well enough to tell you how it needs to be initialized; it doesn’t make sense to me.

As a final comment, if you are going to program in C or C++, you need a basic understanding of pointers and arrays before you can move forward. It’s clear from your post that you are confused over these fundamental concepts.

This material is covered in every introductory C or C++ textbook. I suggest you re-read this material, or Google/Bing for «pointers arrays C» and a number of tutorials will pop up.

Thanks for taking the interest in the post.

But just tell me one thing—how to use a pointer to characters say «name» in which I want to take the entry of the name of the user from keyboard, but the condition is that the size of the string should be exactly the same as the length of name, not a single byte more and not a single byte less. How can I do it in Visual c++?

For a turbo complier I simply use the following code:

#include
int main()
<
char *name;
cout >name;
cout
#include
int main()
<
char *name;
cout

Both code example you posted are not ok. You use the variable «char* name», but you never initialized an amount of memmory that is allocated to this pointer variable. Even if you are not getting an error or warning with your «Turbo compiler» (btw. what «Turbo compiler»? Turbo C++, . ). If you want to handle with dynamic memory you need to use i.e. new or malloc to get a memory block.

From my unserstanding of your problem you should get a good C / C++ book or online tutorial. I guess you did not understand the ifference between a normal variable and pointers. Here a nice tutorial on pointers:

At all I’d recommend the complete C & C++ Programming tutorial for you:

Note: Posted code pieces may not have a good programming style and may not perfect. It is also possible that they do not work in all situations. Code pieces are only indended to explain something particualar.

Thanks to all of you.

You all guided me. I am very happy that you took interest in my problem and mentioned me.

I got what you all were trying explain me.

And learning from your reply I corrected the code and created the CORRECT INFIX TO POSTFIX CONVERTER.

Below is the code. Do have a look at it and please comment how is it. Also please guide me if you still see something misconceptual in my code. I would be very glad to see my silly mistakes. ). Thanks a lot to all of you. ). Learned a lot form you. )

Источник

Error c4700 uninitialized local variable

Hello people, this is my first time using this site so cut me some slack if I have trouble. I am in currently Foundations and Computer Programming II learning how to use C++ in more advance ways. I been given my first assignment and I’ve already came across an error that I don’t know how to fix. The error is «C4700: uninitialized local variable ‘n2’ used» and here is what I have.

void multiply( int , int );

Hey and welcome to this forum. Please make sure to read this post — http://www.cplusplus.com/forum/beginner/1/

And to always use code tags for all of your code — http://www.cplusplus.com/articles/jEywvCM9/

(You can edit your post now and use them to make it more readable)

This is not how the coma operator works. What you want is

Thank you for that tip Tarik, but now I have come across 2 more errors when I made that change. Both of them are error «LNK2019: unresolved external symbol.»

One error says ‘WinMain@16 referenced in function «int_cdel invoke_main(void)» (? invoke_main@@YAHXZ)’

The other one says ‘»void_decl multiply(int,int)» (?multiply@@YAXHH@Z) referenced in function_main’

I think this might be more of a file error, but I’m not sure. I should probably start another forum.

I should probably start another forum.

What does that even mean?

Your problem is simple, your function prototype and your function definition do not look idenetical, which they have to.

void multiply( int , int ); // takes 2 integers

void multiply( int & n1, int n2) // takes 2 integers, but the first one by reference

They have to look the same.

void multiply( int & n1, int n2); // change your function that is in multiply.h to this

Well there goes one of the errors. But the first one is still there.

‘WinMain@16 referenced in function «int_cdel invoke_main(void)» (? invoke_main@@YAHXZ)’

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