Your algorithm is correct for most (all?) standard C headers, but `unistd.h` is not part of standard C so standard C++ in turn doesn&#39;t include it with the other `c...` headers.

Because `unistd.h` never was part of the C language. It is part of the Operating System.

`&lt;unistd.h&gt;` , stands for unix standard header ,the name says it all.

unistd.h is not part of standard C.
Standard C++ lib doesn&#39;t include it with the other c headers.

When I push a new branch up to a remote repository via Git Extensions, I get an alert saying

    The branch {branch name} does not have a tracking reference. Do
    you want to add a tracking reference for {branch name}?

What is a tracking reference?  I&#39;ve found only a few mentions of tracking references in Google and no real definition.

What is a Tracking Reference?

I find myself managing very many files (over 60 but below 70) and my commit messages so far follow this pattern:
when I have added something like on `layout.css`, my commit message is _&quot;added something on layout.css file&quot;_, and when I remove something, my commit message is _&quot;removed something from layout.css file&quot;_.

Some files down the line, I look at my commits feed and _added..._ and  _removed..._ messages dominate. Sometimes I don&#39;t remember what I removed or what I added in `layout.css` since I make so many changes at a go and so I struggle to come up with an appropriate commit message.

Is there a standard I should follow to help me come up with my commit messages?

Standard to follow when writing git commit messages

It&#39;s said that when including C header files in C++, the &quot;.h&quot; suffix should be removed and then add &quot;c&quot; at the beginning. For example, `#include &lt;cstdio&gt;`  instead of `#include &lt;stdio.h&gt;`. But when I use `sleep()` in my code, `#include &lt;cunistd&gt;` does not work, but `#include &lt;unistd.h&gt;` works. Why not `&lt;cunistd&gt;`?

C++ - include unistd.h: why not cunistd?

<p>It's said that when including C header files in C++, the ".h" suffix should be removed and then add "c" at the beginning. For example, <code>#include &#x3C;cstdio></code>  instead of <code>#include &#x3C;stdio.h></code>. But when I use <code>sleep()</code> in my code, <code>#include &#x3C;cunistd></code> does not work, but <code>#include &#x3C;unistd.h></code> works. Why not <code>&#x3C;cunistd></code>?</p>


Recently I created class `Square`:

=========header file======

    class Square
    {
    	int m_row;
    	int m_col;

    public:
    	Square(int row, int col): m_row(row), m_col(col) 
    };



==========cpp file======


    #include &quot;Square.h&quot;
    
    Square::Square(int row, int col)
    {
        cout &lt;&lt; &quot;TEST&quot;;
    }

but then I receive lots of errors. If I remove the cpp file and change the header file to:

=========header file======

    class Square
    {
    	int m_row;
    	int m_col;
    
    public:
    	Square(int row, int col): m_row(row), m_col(col) {};
    };

it complies with no errors. Does it mean that initialization list must appear in the header file?

Is it required to define the initialization list in a header file?

Why does [`string::compare`][1] return an `int` instead of a smaller type like `short` or `char`? My understanding is that this method only returns -1, 0 or 1. 

Second part, if I was to design a compare method that compares two objects of type `Foo` and I only wanted to return -1, 0 or 1, would using `short` or `char` generally be a good idea?

EDIT: I&#39;ve been corrected, `string::compare` does not return -1, 0, or 1, it in fact returns a value &gt;0, &lt;0 or 0. Thanks for keeping me in line guys.

It seems like the answer is roughly, there is no reason to return a type smaller than `int` because return values are &quot;rvalues&quot; and those &quot;rvalues&quot; don&#39;t benefit from being smaller than type int (4 bytes). Also, many people pointed out that the registers of most systems are probably going to be of size `int` anyway, since these registers are going to be filled whether you give them a 1, 2 or 4 byte value, there is no real advantage to returning a smaller value.

EDIT 2: In fact it looks like there may be extra processing overhead when using smaller datatypes such as alignment, masking, etc. The general consensus is that the smaller datatypes exist to conserve on memory when working with a lot of data, as in the case of an array. 

Learned something today, thanks again guys!


  [1]: http://en.cppreference.com/w/cpp/string/basic_string/compare

Why does string::compare return an int?

I&#39;d like to build a `std::string` from a `std::vector&lt;std::string&gt;`.

I could use `std::stringsteam`, but imagine there is a shorter way:

    std::string string_from_vector(const std::vector&lt;std::string&gt; &amp;pieces) {
      std::stringstream ss;

      for(std::vector&lt;std::string&gt;::const_iterator itr = pieces.begin();
          itr != pieces.end();
          ++itr) {
        ss &lt;&lt; *itr;
      }

      return ss.str();
    }

How else might I do this?

How to construct a std::string from a std::vector&lt;string&gt;?

If I am allowed to do the following:

    template &lt;typename T = int&gt;
    class Foo{
    };

Why am I not allowed to do the following in main?

    Foo me;

But I must specify the following:

    Foo&lt;int&gt; me;

C++11 introduced default template arguments and right now they are being elusive to my complete understanding.


Template default arguments

I want to write a `std::string` variable I am accepting from the user to a file. I tried using the `write()` method and it writes to the file. But when I open the file I see boxes instead of the string. 

The string is only a variable length single word. Is `std::string` suitable for this or should I use a character array or something.

    ofstream write;
    std::string studentName, roll, studentPassword, filename;
     

	public:

	void studentRegister()
	{
	    cout&lt;&lt;&quot;Enter roll number&quot;&lt;&lt;endl;
	    cin&gt;&gt;roll;
	    cout&lt;&lt;&quot;Enter your name&quot;&lt;&lt;endl;
	    cin&gt;&gt;studentName;
	    cout&lt;&lt;&quot;Enter password&quot;&lt;&lt;endl;
	    cin&gt;&gt;studentPassword;


	    filename = roll + &quot;.txt&quot;;
        write.open(filename.c_str(), ios::out | ios::binary);

        write.put(ch);
        write.seekp(3, ios::beg);

        write.write((char *)&amp;studentPassword, sizeof(std::string));
        write.close();`
    }

How to write std::string to file?

How does this C program work?

    main(_){_^448&amp;&amp;main(-~_);putchar(--_%64?32|-~7[__TIME__-_/8%8][&quot;&gt;&#39;txiZ^(~z?&quot;-48]&gt;&gt;&quot;;;;====~$::199&quot;[_*2&amp;8|_/64]/(_&amp;2?1:8)%8&amp;1:10);}

It compiles as it is (tested on `gcc 4.6.3`). It prints the time when compiled. On my system:

        !!  !!!!!!              !!  !!!!!!              !!  !!!!!! 
        !!  !!  !!              !!      !!              !!  !!  !! 
        !!  !!  !!              !!      !!              !!  !!  !! 
        !!  !!!!!!    !!        !!      !!    !!        !!  !!!!!! 
        !!      !!              !!      !!              !!  !!  !! 
        !!      !!              !!      !!              !!  !!  !! 
        !!  !!!!!!              !!      !!              !!  !!!!!!

Source: [sykes2 - A clock in one line](http://www.ioccc.org/years-spoiler.html#2006), [sykes2 author hints](http://www.ioccc.org/2006/sykes2/hint.text)

Some hints: No compile warnings per default. Compiled with `-Wall`, the following warnings are emitted:

    sykes2.c:1:1: warning: return type defaults to ‘int’ [-Wreturn-type]
    sykes2.c: In function ‘main’:
    sykes2.c:1:14: warning: value computed is not used [-Wunused-value]
    sykes2.c:1:1: warning: implicit declaration of function ‘putchar’ [-Wimplicit-function-declaration]
    sykes2.c:1:1: warning: suggest parentheses around arithmetic in operand of ‘|’ [-Wparentheses]
    sykes2.c:1:1: warning: suggest parentheses around arithmetic in operand of ‘|’ [-Wparentheses]
    sykes2.c:1:1: warning: control reaches end of non-void function [-Wreturn-type]


Obfuscated C Code Contest 2006. Please explain sykes2.c

So I&#39;m trying trying to use a function defined in another C (file1.c) file in my file (file2.c). I&#39;m including the header of file1 (file1.h) in order to do this.

However, I keep getting the following error whenever I try to compile my file using gcc:

    Undefined symbols for architecture x86_64:
      &quot;_init_filenames&quot;, referenced from:
          _run_worker in cc8hoqCM.o
      &quot;_read_list&quot;, referenced from:
          _run_worker in cc8hoqCM.o
    ld: symbol(s) not found for architecture x86_64

I&#39;ve been told I need to &quot;link the object files together&quot; in order to use the functions from file1 in file2, but I have no clue what that means :(


How do I link object files in C? Fails with &quot;Undefined symbols for architecture x86_64&quot;

I&#39;ve run into memory leaks many times. Usually when I&#39;m `malloc`-ing like there&#39;s no tomorrow, or dangling `FILE *`s like dirty laundry. I generally assume (read: hope desperately) that all memory is cleaned up at least when the program terminates. Are there any situations where leaked memory won&#39;t be collected when the program terminates, or crashes?

If the answer varies widely from language-to-language, then let&#39;s focus on C(++).

Please note hyperbolic usage of the phrase, &#39;like there&#39;s no tomorrow&#39;, and &#39;dangling ... like dirty laundry&#39;. Unsafe* `malloc`*ing can hurt the ones you love. Also, please use caution with dirty laundry.  


How far can memory leaks go?

I&#39;m writing a very small program in C that needs to check if a certain string is empty. For the sake of this question, I&#39;ve simplified my code:

    #include &lt;stdio.h&gt;
    #include &lt;string&gt;

    int main() {
      char url[63] = {&#39;\0&#39;};
      do {
        printf(&quot;Enter a URL: &quot;);
        scanf(&quot;%s&quot;, url);
        printf(&quot;%s&quot;, url);
      } while (/*what should I put in here?*/);

      return(0);
    }

I want the program to stop looping if the user just presses enter without entering anything. 

How to check if C string is empty

I almost understand how tail recursion works and the difference between it and a normal recursion. I **only** don&#39;t understand why it **doesn&#39;t** require stack to remember its return address.


    // tail recursion
    int fac_times (int n, int acc) {
        if (n == 0) return acc;
        else return fac_times(n - 1, acc * n);
    }
         
    int factorial (int n) {
        return fac_times (n, 1);
    }
    
    // normal recursion
    int factorial (int n) {
        if (n == 0) return 1;
        else return n * factorial(n - 1);
    }

There is nothing to do after calling a function itself in a tail recursion function but it doesn&#39;t make sense for me.

Content Type	Original Author	Original Content on Stackoverflow
Question	CDT	View Question on Stackoverflow
Solution 1 - C++	Carl Norum	View Answer on Stackoverflow
Solution 2 - C++	comocomocomocomo	View Answer on Stackoverflow
Solution 3 - C++	Barath Ravikumar	View Answer on Stackoverflow
Solution 4 - C++	babttz	View Answer on Stackoverflow

C++ - include unistd.h: why not cunistd?

C++ Problem Overview

C++ Solutions

Solution 1 - C++

Solution 2 - C++

Solution 3 - C++

Solution 4 - C++

Standard to follow when writing git commit messages

What is a Tracking Reference?

Attributions