C segmentation fault-char pointers?

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I need help figuring out why I am getting a segmentation fault here. I have gone over it and I think I am doing something wrong with the pointers, but I can figure out what. My Program: #include #include void encrypt(char* c); //characters are shifted by 175 int main(){ char* a; *a = 'a'; /*SEGMENTATION FAULT HERE!

*/ encrypt(a); printf("test:%c/n",*a); return 0; }; void encrypt(char* c){ char* result; int i=(int)(*c); i+=175; if(i>255) { i-=256; } *c=(char)i; }; c encryption segmentation-fault link|improve this question asked Mar 11 at 19:38spatara635 100% accept rate.

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– Jonathan Leffler Mar 11 at 19:41.

The problem is here: char *a; *a = 'a' Since the variable "a" is not initialized, *a = 'a' is assigning to a random memory location. You could do something like this: char a1; a0 = 'a'; encrypt(&a0); Or even just use a single character in your case: int main(){ char a = 'a'; encrypt(&a); printf("test:%c/n",a); return 0; }.

That worked! Thanks! – spatara Mar 11 at 19:46.

Char* a; *a = 'a'; /*SEGMENTATION FAULT HERE! */ There isn't any "there" there. You've declared a and left it uninitialized.

Then you tried to use it as an address. You need to make a point to something. One example: char buffer512; char *a = buffer; (Note buffer has a maximum size and when it falls out of scope you cannot reference any pointers to it.

) Or dynamic memory: char *a = malloc(/* Some size... */); if (!a) { /* TODO: handle memory allocation failure */ } // todo - do something with a. Free(a).

That pointer a does not get the actual space where to store the data. You just declare the pointer, but pointing to where? You can assign memory this way: char *a = malloc(1); Then it won't segfault.

You have to free the variable afterwards: free(a); But in this case, even better, char a = 'a'; encript(&a).

Malloc(1) seems like a heavy-weight way of dealing with this particular example. – Jonathan Leffler Mar 11 at 19:45 Yes, well, you're right. Just wanted to show some patterns for assigning dynamic memory.

– Diego Sevilla Mar 11 at 19:45 Thanks! This is also a good solution :) – spatara Mar 11 at 19:47.

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