From mboxrd@z Thu Jan  1 00:00:00 1970
From: John Richard Moser <nigelenki@comcast.net>
Subject: Variable Declaration Order
Date: Thu, 01 Jul 2004 13:54:05 -0400
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When declaring variables, what order do you all declare them in?  I
usually follow the following scheme:

struct foo {
	int *ptr;
	struct bar other_structs;
	int fixed_val;
	float fixed_float;
	char array[2];
};

int baz() {
	char array[2];
	int fixed_val;
	float fixed_float;
	struct foo other_structs;
	int *ptr;
}

The idea is to make sure that the arrangement in memory is always

[PTR ][NORM][AL  ][ARRAY]

if possible; but to try to keep arrays on the right side, and pointers
on the left.  Structures should be handled VERY carefully to assure that
no pointers are to the right of arrays.  If a structure has a pointer
and an array, and two structures need to be in the same allocation unit,
such as:

struct bar {
	int *ptr;
	char array[2];
};

struct foo {
	int *ptr;
	struct bar other_structs;
	struct bar other_structs;
	int fixed_val;
	float fixed_float;
	char array[2];
};

int baz() {
	char array[2];
	int fixed_val;
	float fixed_float;
	struct foo other_structs;
	struct foo other_structs;
	int *ptr;
}

Then they need to be pointers to avoid pointer clobbering:

struct bar {
	int *ptr;
	char array[2];
};

struct foo {
	int *ptr;
	struct bar *other_structs;
	struct bar *other_structs2;
	int fixed_val;
	float fixed_float;
	char array[2];
};

int baz() {
	char array[2];
	int fixed_val;
	float fixed_float;
	struct foo *other_structs;
	struct foo *other_structs2;
	int *ptr;
	other_structs = initNewFoo();
	other_structs2 = initNewFoo();
}

This is the variable order I tend to use to avoid nasty things from
programming bugs.  The point of putting fixed length values (int, float,
etc) after pointers is so that a missplaced cast (i.e. &achar passed to
a function expecting an int*) don't clobber the pointer, allowing
certain situations to allow someone who knows just how to set the bug
off to make the program do arbitrary memory writes.

I use ProPolice; so on the stack, the end of the stack frame has a
canary that gets clobbered if that first array overflows

Anyone have a better scheme, or see a flaw in my order?
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