Add:

    #include &lt;stdlib.h&gt;

to the top of your program.

Do you have this preprocessor?  If not, add it.

    #include &lt;stdlib.h&gt;

exit() is a library function, the respecive prototypes are present in  the **stdlib.h** header file, inoder to call the process to specified code for exit function, you need to attach the as **#include stdlib.h** header in your program. that is the reason we  should add the stdlib.h header. eventhough you can run the program, but it shows the warning message like below:  

    warning: incompatible implicit declaration of built-in function ‘exit’ [enabled by default]      
 
  
but, this kind of program not recommended, we need to take care of what we are given in the program,be cautious. 
warning may leads runtime error.


I have Activity `A` with `android:launchMode=&quot;singleTop&quot;` in the manifest.

If I go to Activity `B`, `C`, and `D` there I have menu shortcuts to return to my applications root activity (`A`).

The code looks like this:

    Intent myIntent = new Intent(getBaseContext(), MainActivity.class);
    startActivity(myIntent);

However, instead of returning to the already existing instance `A` of my `MainActivity.class` it creates a new instance -&gt; it goes to `onCreate()` instead of `onNewIntent()`.

This is not the expected behavior, right?

New Intent() starts new instance with Android: launchMode=&quot;singleTop&quot;

In SQLServer, you can use syntax &quot;(nolock)&quot; to ensure the query doesn&#39;t lock the table or isn&#39;t blocked by other queries locking the same table.
e.g.

    SELECT * FROM mytable (nolock) WHERE id = blah

What&#39;s the equivalent syntax in Postgres? I found some documentation on table locking in PG (http://www.postgresql.org/docs/8.1/interactive/sql-lock.html), but it all seems geared at how to *lock* a table, not ensure it&#39;s *not locked*.

PostgreSQL Equivalent of SQLServer&#39;s NoLock Hint

This is my warning. 
  

    implicit declaration of function &#39;exit&#39;

How i can remove it.

i am using linux &amp; gcc compiler.

C warning implicit declaration of function &#39;exit&#39;

This is my warning.
<pre><code class="hljs language-bash">implicit declaration of function 'exit'
</code></pre>
How i can remove it.
i am using linux &#x26; gcc compiler.

In gcc command line, I want to define a string such as `-Dname=Mary`, then in the source code I want `printf(&quot;%s&quot;, name);` to print `Mary`.  
How could I do it?


How to define a string literal in gcc command line?

I was curious to know how I can round a number to the nearest whole number. For instance, if I had:

    int a = 59 / 4;

which would be 14.75 if calculated in floating point; how can I store the result as 15 in &quot;a&quot;?



Rounding integer division (instead of truncating)

I want to know the difference between a file descriptor and file pointer.

Also, in what scenario would you use one instead of the other?

What&#39;s the difference between a file descriptor and file pointer?

I want to know how and when can I use the `exit()` function like the program in my book:

    #include&lt;stdio.h&gt;
    
    void main()
    {
        int goals;
        printf(&quot;enter number of goals scored&quot;);
        scanf(&quot;%d&quot;,&amp;goals);
    
        if(goals&lt;=5)
            goto sos;
        else
        {
            printf(&quot;hehe&quot;);
            exit( );
        }
        sos:
        printf(&quot;to err is human&quot;);
    }

When I run it, it shows ERROR: *call to undefined function exit()*.

Also, I want to know how I can create an option to close the window in which the program runs? For example, I made a menu-driven program which had several options and one of them was *&quot;exit the menu&quot;*. How can I make this exit the program (i.e. close the window)?

Use of exit() function

I want to know the disadvantages of `scanf()`.

In many sites, I have read that using `scanf` might cause buffer overflows. What is the reason for this? Are there any other drawbacks with `scanf`?

Disadvantages of scanf

For instance:

    Bool NullFunc(const struct timespec *when, const char *who)
    {
       return TRUE;
    }

In C++ I was able to put a `/*...*/` comment around the parameters. But not in C of course, where it gives me the error:

&gt; error: parameter name omitted





How can I suppress &quot;unused parameter&quot; warnings in C?

I would like to enable -- literally -- **ALL** of the warnings that GCC has. (You&#39;d think it would be easy...)

- You&#39;d think `-Wall` might do the trick, but nope! Still need `-Wextra`.

- You&#39;d think `-Wextra` might do the trick, but nope! Not all of the warnings listed [here](http://gcc.gnu.org/onlinedocs/gcc-4.4.0/gcc/Warning-Options.html) (for example, `-Wshadow`) are enabled by this. And I still have no idea if this list is comprehensive.

How do I tell GCC to enable (no if&#39;s, and&#39;s, or but&#39;s!) **all** the warnings it has?

How to turn on (literally) ALL of GCC&#39;s warnings?

    #include &lt;stdio.h&gt;

    volatile int i;

    int main()
    {
        int c;

        for (i = 0; i &lt; 3; i++) 
        {
             c = i &amp;&amp;&amp; i;
             printf(&quot;%d\n&quot;, c);
        }

        return 0;
    }

The output of the above program compiled using `gcc` is

    0
    1
    1

With the `-Wall` or `-Waddress` option, `gcc` issues a warning:

    warning: the address of ‘i’ will always evaluate as ‘true’ [-Waddress]

How is `c` being evaluated in the above program?


What is &amp;&amp;&amp; operation in C

I have a header file suppose abc.h, where i have function declaration as:

    static int function1();

I have included this header file in abc.c and has defined the function and used it.


    static int function1()
    {
     &lt; function definition&gt;
    }

After compiling I am getting warning:

    warning: function1 declared static but never defined


How can I remove warning, without removing static.
Thanks.

function declared static but never defined

I&#39;m trying to compile and run following program without `main()` function in `C`. I have compiled my program using the following command.

    gcc -nostartfiles nomain.c
And compiler gives warning

    /usr/bin/ld: warning: cannot find entry symbol _start; defaulting to 0000000000400340

Ok, No problem. then, I have run executable file(a.out), both `printf` statements print successfully, and then get **segmentation fault**. 

So, my question is, **Why segmentation fault after successfully execute print statements?**

my code:

    #include &lt;stdio.h&gt;

    void nomain()
    {
            printf(&quot;Hello World...\n&quot;);
            printf(&quot;Successfully run without main...\n&quot;);
    }

**output:**

&lt;!-- language: lang-none --&gt;

    Hello World...
    Successfully run without main...
    Segmentation fault (core dumped)

**Note:** 

Here, `-nostartfiles` gcc flag prevents the compiler from using standard startup files when linking


Content Type	Original Author	Original Content on Stackoverflow
Question	ambika	View Question on Stackoverflow
Solution 1 - C	Greg Hewgill	View Answer on Stackoverflow
Solution 2 - C	shinkou	View Answer on Stackoverflow
Solution 3 - C	prashad	View Answer on Stackoverflow

C warning implicit declaration of function 'exit'

C Problem Overview

C Solutions

Solution 1 - C

Solution 2 - C

Solution 3 - C

PostgreSQL Equivalent of SQLServer's NoLock Hint

New Intent() starts new instance with Android: launchMode="singleTop"

Attributions