Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>The pointer cast is completely unnecessary. If your program appears to work, it's an unlucky coincidence. (I say "unlucky" because it means the error is not being diagnosed.)</p> <p><code>localtime()</code> takes an argument of type <code>const time_t*</code>, <em>not</em> <code>clock_t*</code>. <code>time_t</code> and <code>clock_t</code> are distinct types, used for different purposes, even though they <em>might</em> happen to be defined in the same way in some particular implementation.</p> <p>Change the definition of <code>now</code> to:</p> <pre><code>time_t now; </code></pre> <p>and call <code>localtime</code> like this:</p> <pre><code>mac_time = localtime(&amp;now); </code></pre> <p>Any cast, especially a pointer cast, should be viewed with suspicion. Casts are too often used to silence compiler warnings, when the real solution is to fix your code so things are declared with the correct type in the first place.</p> <p>As for the question you're asking -- well, it doesn't matter much, since the code is fundamentally incorrect. This:</p> <pre><code>mac_time = localtime((const long *)&amp;now) </code></pre> <p>takes the address of <code>now</code> (which, in your code, is of type <code>clock_t*</code>) and converts it to <code>const long*</code>. Since <code>localtime</code> expects an argument of type <code>const time_t*</code>, and <em>apparently</em> <code>time_t</code> is defined as <code>long</code> on your implementation, this <em>appears</em> to work.</p> <p>This:</p> <pre><code>mac_time = localtime(&amp;(const long *)now); </code></pre> <p>takes the <em>value</em> of <code>now</code> (which at this point has not been initialized) and converts it to a <code>const long*</code>; in other words, it takes a garbage numeric value and converts it to a pointer. It then attempts to take the address of that pointer -- but since it's a pointer <em>value</em>, not a pointer <em>object</em>, it has no address. The above is a compile-time error. (I'd expect your compiler to treat this as a fatal error, not just a warning.)</p> <p>But forget all that. Just declare your objects to be of the correct types in the first place, and you won't have to worry about casts.</p> <p>(There are cases where casts, even pointer casts, are necessary and appropriate, but not for what you're trying to do here.)</p>
    singulars
    1. This table or related slice is empty.
    1. POCall by reference value's type casting in Unix
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USKeith Thompson
    1. USKeith Thompson
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. This table or related slice is empty.
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload