Difference between revisions of "0051"
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Junior Djjr (talk | contribs) (Created page with "{{OpCode | games = {{Icon|t}} | command = RETURN | description = Return from the current subroutine. | syntax1 = 0051: return | p1t = ''none'' }} After...") |
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| − | + | This opcode returns from the current subroutine. | |
| + | When the script encounters a [[0051]], it will return from where the last [[0050]] was called. | ||
The game will crash if: | The game will crash if: | ||
* [[0051]] was read before any [[0050]] was called. | * [[0051]] was read before any [[0050]] was called. | ||
| + | |||
| + | == Implementation == | ||
| + | See ''[[0050#Implementation|gosub]]'' for further details. | ||
| + | |||
| + | <syntaxhighlight lang="cpp"> | ||
| + | /* Note: This is not real code and will not compile. */ | ||
| + | /* Based on decompilation of SA v2.0 */ | ||
| + | |||
| + | /* | ||
| + | The game will crash if the call stack is empty | ||
| + | (i.e. script->callStackPosition == 0), because | ||
| + | script->callStackPosition - 1 would be -1, and | ||
| + | therefore an invalid index. | ||
| + | |||
| + | This can happen if "return" is used outside a | ||
| + | subroutine. | ||
| + | */ | ||
| + | |||
| + | // Move up to the previous stack frame. | ||
| + | script->callStackPosition = script->callStackPosition - 1; | ||
| + | |||
| + | // Set the current offset to the previous one. | ||
| + | // The previous offset will be the offset of the next instruction after the ''gosub''. | ||
| + | script->readPointer = (&script->callStack)[script->callStackPosition]; | ||
| + | </syntaxhighlight> | ||
== Keywords == | == Keywords == | ||
subroutine, gosub, go sub | subroutine, gosub, go sub | ||
Latest revision as of 15:07, 1 July 2021
RETURN
- Description
- Return from the current subroutine.
- Syntax
- 0051: return
- Parameter
- none
This opcode returns from the current subroutine. When the script encounters a 0051, it will return from where the last 0050 was called.
The game will crash if:
Implementation
See gosub for further details.
/* Note: This is not real code and will not compile. */
/* Based on decompilation of SA v2.0 */
/*
The game will crash if the call stack is empty
(i.e. script->callStackPosition == 0), because
script->callStackPosition - 1 would be -1, and
therefore an invalid index.
This can happen if "return" is used outside a
subroutine.
*/
// Move up to the previous stack frame.
script->callStackPosition = script->callStackPosition - 1;
// Set the current offset to the previous one.
// The previous offset will be the offset of the next instruction after the ''gosub''.
script->readPointer = (&script->callStack)[script->callStackPosition];Keywords
subroutine, gosub, go sub
