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POWhy can't I assign values to pointers?
 

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  1. POWhy can't I assign values to pointers?
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    <p>After reading the faq's and everything else I can find, I'm still confused. If I have a char pointer that is initialised in this fashion:</p> <p><code>char *s = "Hello world!"</code></p> <p>The string is in read-only memory and I cannot change it like this:</p> <pre><code>*s = 'W'; </code></pre> <p>to make "Wello world!". This I understand, but I can't, for the life of me, understand how to make it NOT read-only. Do I have to use an array instead of a pointer? Like <a href="https://stackoverflow.com/questions/164194/why-does-simple-c-code-receive-segmentation-fault">here</a>?</p> <p>This is my code: </p> <pre><code>char *s = str; char *e = s; while (*e != '\0') e++; e--; char *temp; //Swop the string around while (s &lt;= e) { *temp = *s; *s = *e; *e = *temp; e--; s++; } </code></pre> <p>The error message is just a segmentation fault. Apologies in advance if this is a really stupid question. </p> <p>Thanks so much for all the help. After taking all your advice, I get this:</p> <pre><code>void something(char * str) { char *store = str; char *s = new char[strlen(str) + 1]; //Allocate memory. Nice one. strcpy(s, str); char *e = new char[strlen(str) + 1]; strcpy(e, str); while (*e != '\0') e++; e--; char temp; //no longer a pointer while (s &lt;= e) { cout &lt;&lt; *e; temp = *s; *s = *e; *e = temp; e--; s++; } delete [] e; delete [] s; } </code></pre> <p>however, the deletes at the end of the function seem to be causing their own segmentation faults. Why? </p> <p>For interest's sake: The faults were due to accessing the e and s pointers after they were incremented. A much simpler solution followed from that:</p> <pre><code>void something(char * str) { char *s = new char[strlen(str) + 1]; strcpy(s, str); char temp; int j = strlen(str) - 1; for (int i = 0; i &lt;= strlen(str)/2; i++) { cout &lt;&lt; s &lt;&lt; endl; temp = s[i]; s[i] = s[j]; s[j] = temp; j--; } delete [] s; } </code></pre>
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    1. COThe way I read this, your *s = 'W' is just an example of something you know you can't do? It has nothing to do with the code below, which is what you actually want help with? Just asking because most of the answers seem to focus on the first example
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    2. COYes, I know I can't do that :( I was wondering about how to do it correctly. I've implemented all the advice, so maybe if you can have another looksy?
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    3. CODo what correctly? I'm still a bit unclear on what your question is. You're trying to reverse a string, it seems? I'm just not sure if the "*s = 'W'" part had any relevance to the question itself. Also if the deletes cause segfaults, you'll need to post those too.
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