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Top Forums Programming Unexplained segmentation fault Post 302508195 by achenle on Saturday 26th of March 2011 01:58:40 PM
Old 03-26-2011
Quote:
Originally Posted by Corona688
Code:
char *buf;

This doesn't create memory for you. All a pointer is is an integer describing where memory is. ...

Arrgh! No! Not that! Smilie

Seriously, in order to be perfectly clear: while a pointer may be an integer-type value, a pointer is NOT an int, nor a long, nor an unsigned int or unsigned long. A pointer is a pointer. Just because it might be the same number of bytes as a some specfic integer-type variable for whatever architecture you're coding in, that doesn't mean that relationship will hold for other architectures.

Along the same lines, size_t is size_t, NOT unsigned int.

If you screw that up and get it ingrained into your programming practices, when you move to another architecture (Can you say "64 bits"? Thank you, I knew you could!), you'll have some serious problems.
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memory(3C)						   Standard C Library Functions 						memory(3C)

NAME
memory, memccpy, memchr, memcmp, memcpy, memmove, memset - memory operations SYNOPSIS
#include <string.h> void *memccpy(void *restrict s1, const void *restrict s2, int c, size_t n); void *memchr(const void *s, int c, size_t n); int memcmp(const void *s1, const void *s2, size_t n); void *memcpy(void *restrict s1, const void *restrict s2, size_t n); void *memmove(void *s1, const void *s2, size_t n); void *memset(void *s, int c, size_t n); ISO C++ #include <string.h> const void *memchr(const void *s, int c, size_t n); #include <cstring> void *std::memchr(void *s, int c, size_t n); DESCRIPTION
These functions operate as efficiently as possible on memory areas (arrays of bytes bounded by a count, not terminated by a null charac- ter). They do not check for the overflow of any receiving memory area. The memccpy() function copies bytes from memory area s2 into s1, stopping after the first occurrence of c (converted to an unsigned char) has been copied, or after n bytes have been copied, whichever comes first. It returns a pointer to the byte after the copy of c in s1, or a null pointer if c was not found in the first n bytes of s2. The memchr() function returns a pointer to the first occurrence of c (converted to an unsigned char) in the first n bytes (each interpreted as an unsigned char) of memory area s, or a null pointer if c does not occur. The memcmp() function compares its arguments, looking at the first n bytes (each interpreted as an unsigned char), and returns an integer less than, equal to, or greater than 0, according as s1 is lexicographically less than, equal to, or greater than s2 when taken to be unsigned characters. The memcpy() function copies n bytes from memory area s2 to s1. It returns s1. If copying takes place between objects that overlap, the behavior is undefined. The memmove() function copies n bytes from memory area s2 to memory area s1. Copying between objects that overlap will take place cor- rectly. It returns s1. The memset() function sets the first n bytes in memory area s to the value of c (converted to an unsigned char). It returns s. USAGE
Using memcpy() might be faster than using memmove() if the application knows that the objects being copied do not overlap. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
string(3C), attributes(5), standards(5) SunOS 5.10 1 Nov 2003 memory(3C)
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