From 7e0f021a9aec35fd8e6725e87e3313b101d26f5e Mon Sep 17 00:00:00 2001 From: Tobias Klauser Date: Sun, 27 Jan 2008 11:37:44 +0100 Subject: Initial import (2.0.2-6) --- reference/C/FUNCTIONS/malloc.html | 123 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 reference/C/FUNCTIONS/malloc.html (limited to 'reference/C/FUNCTIONS/malloc.html') diff --git a/reference/C/FUNCTIONS/malloc.html b/reference/C/FUNCTIONS/malloc.html new file mode 100644 index 0000000..d4f7e0f --- /dev/null +++ b/reference/C/FUNCTIONS/malloc.html @@ -0,0 +1,123 @@ +malloc function + + + + + + +

+ +

malloc function

+ +

+malloc (memory allocation) is used to dynamically allocate memory +at run time. Possible uses for this function are: + +

Read records of an unknown length. +
Read an unknown number of database records. +
Link lists. +

+ +The simplest way to reserve memory is to code something like: +

+ + + + +
+
+ + main() + { + char string[1000]; + + strcpy (string, "Some text"); + } +
+
+

+The example above has two problems: +

If the data is less than + +1000 bytes we are wasting memory. +
If the data is greater than 1000 bytes the program is going to crash. +
The 1000 bytes are reserved throught out the life of the program. +If this was a long running program that rarely used the memory, it would +again be wasteful. +

+malloc allows us to allocate exactly the correct amount of memory and +with the use of free only for the time it is required. +

+	Library:   stdlib.h
+
+	Prototype: void *malloc(size_t size);
+
+	Syntax:    char * String;
+
+                   String = (char *) malloc(1000);
+

+Looking at the example syntax above, 1000 bytes are reserved and the pointer +String points to the first byte. The 1000 bytes are NOT initialized +by malloc. If the memory is NOT available, a +NULL pointer is returned. + +Please note, the cast cast is required to +return a pointer of the correct type. +