memvis

A small C/C++ header that draws address blocks and the values they hold as plain-text diagrams.

Copy memvis.h into your project, #include it from a .c / .cpp file, and call memvis(). The diagrams print to stdout (terminal or a log if you redirect). The idea is to stay lightweight, readable on a console, and useful when you are still getting comfortable with pointers.

It is early (v0.1). The supported types are growing one at a time.

Why this exists

Pointers are easier to reason about when you can see:

• the address of a variable
• the value stored there
• and, for pointers, what the next hop actually points at

memvis is meant for that: debugging messy allocations, and teaching / learning int*, int**, arrays, and now char / char[].

What it can draw today

VAR_TYPE_t	What you pass
INTEGER	address of an int (byte-by-byte, so endianness is visible)
CHAR	address of a char
INTEGER_ARRAY	int array (or pointer + length)
CHAR_ARRAY	char array
POINTER_TO_POINTER_TO_INTEGER	address of an int** (&pp)
ARRAY_OF_N_POINTER_TO_INTEGER	array of int*

CUSTOM, DOUBLE, and a few other enum values are placeholders. They are not implemented yet.

Quick start

memvis is a single header. Copy memvis.h into your project, include it from a .c / .cpp file, and call memvis().

#include "memvis.h"

int n = 42;
memvis(&n, INTEGER, 0);

cc example.c -o example
./example

Type-by-type arguments, how to read each diagram, and the usual pitfalls are commented in example.c. That file is the usage guide; compile it and you get the visualization too.

Addresses in the diagrams are from your process. They will not match the sample below.

Example

example.c is the usage guide: a file-level comment on the API, then one commented section per type (int *[], int array, char array, int **, byte-split int, single char).

Sample run (addresses from one machine; yours will differ):

Output of example.c

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE: ARRAY_OF_N_POINTER_TO_INTEGER
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
| 0x7ffee76d1650   | 0x7ffee76d1654   | 0x7ffee76d1658   |
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
 0x7ffee76d1690     0x7ffee76d1698     0x7ffee76d16a0



REPRESENTATION OF POINTER TO Integer IN INDEX 0
++++++++++++++++++
| 100            |
++++++++++++++++++
 0x7ffee76d1650



REPRESENTATION OF POINTER TO Integer IN INDEX 1
++++++++++++++++++
| 101            |
++++++++++++++++++
 0x7ffee76d1654



REPRESENTATION OF POINTER TO Integer IN INDEX 2
++++++++++++++++++
| 102            |
++++++++++++++++++
 0x7ffee76d1658


--------------------MEMVIS REPRESENTATION END----------------------

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE: Integer Array
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
| 1                | 2                | 3                | 4                | 5                |
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
 0x7ffee76d1670     0x7ffee76d1674     0x7ffee76d1678     0x7ffee76d167c     0x7ffee76d1680


--------------------MEMVIS REPRESENTATION END----------------------

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE: Character Array
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
| M                | E                | M                | V                | I                | S                |
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
 0x7ffee76d16b1     0x7ffee76d16b2     0x7ffee76d16b3     0x7ffee76d16b4     0x7ffee76d16b5     0x7ffee76d16b6


--------------------MEMVIS REPRESENTATION END----------------------

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE:


REPRESENTATION OF POINTER(pp) HOLDING THE ADDRESS OF THE POINTER HOLDINGTHE ADDRESS OF THE Integer VARIABLE
++++++++++++++++++
|0x7ffee76d1668  | ==> pp
++++++++++++++++++
 0x7ffee76d1660   ==> &pp

REPRESENTATION OF THE POINTER HOLDING THE ADDRESS OF THE INTEGER VARIABLE
++++++++++++++++++
|0x5596ea107420  | ==> *pp
++++++++++++++++++
 0x7ffee76d1668   ==> pp

REPRESENTATION OF THE INTEGER VARIABLE AND THE VALUE IT IS HOLDING
++++++++++++++++++
| 3784          | ==> **pp
++++++++++++++++++
 0x5596ea107420   ==> *pp


--------------------MEMVIS REPRESENTATION END----------------------

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE: Integer
I am Little Endian
The value is = 0x12345678

My Starting Address : 0x7ffee76d165c

|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
| 78               | 56               | 34               | 12               |
|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|++++++++++++++++++|
 0x7ffee76d165c     0x7ffee76d1664     0x7ffee76d166c     0x7ffee76d1674


--------------------MEMVIS REPRESENTATION END----------------------

--------------------MEMVIS REPRESENTATION START--------------------
MEMVIS VAR TYPE: Character
|++++++++++++++++++|
| M                |
|++++++++++++++++++|
 0x7ffee76d164f


--------------------MEMVIS REPRESENTATION END----------------------

How to read a block: the middle row is the stored value (or a pointer), the row under it is the address of that cell.

For INTEGER, memvis splits the value into bytes so you can see endianness. On little-endian, 0x12345678 shows up as 78 56 34 12.

CHAR / CHAR_ARRAY print the character in the cell, not a numeric code.

Contributing

Issues and PRs are welcome. Check the issue list first — there are bugs and features already written down.

This library is supposed to stay small and predictable. Please send a change you actually understand, and that you have run against example.c (or a similar snippet). Generated dumps that you have not read through will get closed.

License

MIT. See LICENSE.