Databases
StackOverflow2013
Postsdbo
POHow C strings are allocated in memory?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow C strings are allocated in memory?
    primarykey
    data
    text
    <p>Say I have a simple function that returns a C string this way:</p> <pre><code>const char * getString() { const char * ptr = "blah blah"; return ptr; } </code></pre> <p>and I call getString() from main() this way:</p> <blockquote> <pre><code> const char * s = getString(); </code></pre> </blockquote> <p>1) According to gdb, the variable <strong>ptr</strong> is stored on the stack, but <em>the string pointed by ptr</em> is not:</p> <pre><code>(gdb) p &amp;ptr $1 = (const char **) 0x7fffffffe688 (gdb) p ptr $2 = 0x4009fc "blah blah" </code></pre> <p>Does this mean that "blah blah" is not a local variable inside getString()? </p> <p>I guess that if it were a local variable, I would not be able to pass it to my main() function... But if it's not, where is it stored? On the heap? Is that a "kind of" dynamically memory allocation implemented by the OS every time it hits on a string, or what?</p> <p>2) If I use an array instead of a pointer, this way:</p> <pre><code>const char *getString2() { const char a[] = "blah blah blah"; return a; } </code></pre> <p>the compiler warns me that: </p> <p><code>warning: address of local variable ‘a’ returned</code></p> <p>(and of course the program compiles, but it doesn't work).</p> <p>Actually, if I ask gdb, I get</p> <pre><code>(gdb) p &amp;a $2 = (const char (*)[15]) 0x7fffffffe690 </code></pre> <p>But I thought that <strong>const char * ptr</strong> and <strong>const char a[]</strong> were basically the same thing. Looks like they're not.</p> <p>Am I wrong? What is exactely the difference between the two versions?</p> <p>Thank you! </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. This table or related slice is empty.
    1. USlaurids
    plurals
    1. PL
      singulars
      1. LTLinked
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow C strings are allocated in memory?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow C strings are allocated in memory?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow C strings are allocated in memory?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COhttp://stackoverflow.com/questions/3862842/difference-between-char-str-string-and-char-str-string
      singulars
      1. POHow C strings are allocated in memory?
      1. USMat
    2. COWell formulated question, even if it's a repeat.
      singulars
      1. POHow C strings are allocated in memory?
      1. USMats Petersson
 

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