Heap and stack Post: 302189900

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Top Forums Programming Heap and stack Post 302189900 by jim mcnamara on Monday 28th of April 2008 07:25:21 AM

04-28-2008

Registered User

Code:

main()
{
int *a;
.
.
}

a, itself, is on the stack. What part of memory a "is aimed at" is indeterminate in your code. It could be anywhere. Show us something like a=&some_int and then we can tell you. As it is there is no way to answer.

Next problem - gets works on string pointers, not int *
So I have no idea where gets would be working.

If you are worried about heap being "slower" than stack, don't. Unless you can definitely show that a gets call is a bottleneck - by using a profiler - it is a waste of programmer time to fuss over stuff like that.

gets works against the actual memory referenced by the pointer, it has nothing to do with where the pointer itself lives.

Andryk - void main () is a BAD idea, especially in a UNIX forum.

jim mcnamara

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STACK(9)						   BSD Kernel Developer's Manual						  STACK(9)

NAME

     STACK -- stack macros

SYNOPSIS

     #include <sys/param.h>

     type
     STACK_ALLOC(sp, size);

     type
     STACK_MAX(sp, size);

     type
     STACK_ALIGN(sp, bytes);

     type
     STACK_GROW(sp, size);

     type
     STACK_SHRINK(sp, size);

DESCRIPTION

     A stack is an area of memory with a fixed origin but with a variable size.  A stack pointer points to the most recently referenced location
     on the stack.  Initially, when the stack has a size of zero, the stack pointer points to the origin of the stack.	When data items are added
     to the stack, the stack pointer moves away from the origin.

     The STACK_ALLOC() macro returns a pointer to allocated stack space of some size.  Given the returned pointer sp and size, STACK_MAX() returns
     the maximum stack address of the allocated stack space.  The STACK_ALIGN() macro can be used to align the stack pointer sp by the specified
     amount of bytes.

     Two basic operations are common to all stacks: a data item is added (``push'') to the location pointed by sp or a data item is removed
     (``pop'') from the stack.	The stack pointer must be subsequently adjusted by the size of the data item.  The STACK_GROW() and STACK_SHRINK()
     macros adjust the stack pointer sp by given size.

     A stack may grow either up or down.  The described macros take this into account by using the __MACHINE_STACK_GROWS_UP preprocessor define.

SEE ALSO

     param(3), queue(3)

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