Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>Wow. What you're trying to do is a complete abuse of C++, would be totally compiler dependent if it worked, and would surely land you in TheDailyWTF some day.</p> <p>The reason you're getting a segfault is probably because your operator= is reallocating the object to a different address, but you're not updating the myString pointer in main. I hesitate to even call it an object at this point, since no constructor was ever called.</p> <p>I think what you're trying to do is make pString a smarter pointer to a string, but you're going about it all wrong. Let me take a crack at it.</p> <pre><code>#include &lt;iostream&gt; using namespace std; class pString { public: char * c; pString &amp; operator=(const char *); const char * c_str(); }; pString &amp; pString::operator=(const char * buff) { cout &lt;&lt; "Address of this: " &lt;&lt; (uint32_t) this &lt;&lt; endl; cout &lt;&lt; "Address of this-&gt;c: " &lt;&lt; (uint32_t) this-&gt;c &lt;&lt; endl; c = (char *) malloc(strlen(buff)+1); memcpy(c, buff, strlen(buff)); *(c+strlen(buff)) = '\0'; return *this; }; const char * pString::c_str() { return c; } int main() { pString myString; myString = "testing"; cout &lt;&lt; "'" &lt;&lt; myString.c_str() &lt;&lt; "'"; </code></pre> <p>}</p> <p>Now I wouldn't use malloc but new/delete instead, but I left this as close to your original as possible.</p> <p>You <b>might think</b> you are wasting the space of a pointer in your class, but you aren't - you're trading it for the pointer you previously kept in main. I hope this example makes it clear - the variables are the same size, and the amount of additional memory allocated by malloc/realloc is the same as well.</p> <pre><code>pString myString; char * charString; assert(sizeof(myString) == sizeof(charString)); </code></pre> <p>P.S. I should point out that this code still needs a lot of work, it's full of holes. You need a constructor to initialize the pointer, and a destructor to free it when it's done, just for starters. You can do your own implementation of operator+, too.</p>
    singulars
    1. This table or related slice is empty.
    1. PORealloc()/Resize an object in C++ for a string implementation
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USMark Ransom
    1. USMark Ransom
    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. COIt's pretty close to what i'm looking for, but not exactly. sizeof(pString) is still going to be 8 even for a blank string and pString-Cstring is not internally the same e.g. printf("%s", (char*)myPstring); won't work.
      singulars
      1. PO
      1. USBen Reeves
    2. COsizeof(char *) is going to be 8 for a blank string as well. You can create an operator char *() if you want automatic conversion of the class to a pointer, but I'd make it operator const char *() instead. Explicit c_str() is safer and matches std::string.
      singulars
      1. PO
      1. USMark Ransom
    3. COOh, I assume you are using a 64-bit compiler when you say sizeof(pString) will be 8; if it's 32 bit, sizeof(pString) will be 4. There's only one data member, and it's a pointer.
      singulars
      1. PO
      1. USMark Ransom
 

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