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Add ASCII art representing the basic struct layout.

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* libguile/struct.h: Add ASCII art version of the basic struct layout as
  shown in Andy's diagrams.
This commit is contained in:
Ludovic Courtès 2010-01-25 23:43:41 +01:00
parent 227eff6a77
commit bb190ddbba
1 changed files with 29 additions and 1 deletions
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30
libguile/struct.h
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@ -33,9 +33,37 @@
in turn means we need support for changing the "class" (vtable) of an
"instance" (struct). This necessitates some indirection and trickery.
I would like to write this all up here, but for now:
To summarize, structs are laid out this way:
.-------.
| |
.----------------+---v------------- -
| vtable | data | slot0 | slot1 |
`----------------+----------------- -
| .-------.
| | |
.---v------------+---v------------- -
| vtable | data | slot0 | slot1 |
`----------------+----------------- -
|
v
...
.-------.
| | |
.---v------------+---v------------- -
.-| vtable | data | slot0 | slot1 |
| `----------------+----------------- -
| ^
`-----'
The DATA indirection (which corresponds to `SCM_STRUCT_DATA ()') is necessary
to implement class redefinition.
For more details, see:
http://wingolog.org/archives/2009/11/09/class-redefinition-in-guile
*/
/* All vtables have the following fields. */