Short: replace_program() and virtual variables
From: Lars, Zonk
Date: 2003-01-19
Type: Bug
State: New

replace_program() can replace with a program only if it either doesn't
have virtually inherited variables, or is the first program inherited.

Reason is that replace_program() expects the variables of the program
in one block, starting at variable_index_offset. However, with virtual
inherites the virtually inherited variables are collected in a block
at the beginning of the variable block, so that replace_program() extracts
the wrong variables during the replacement. Only if the replaced program happens
to be the first inherited program, the variable_index_offset is 0 and
the extraction code by accident does the right thing.

The proper solution would be to use the inheritance/variable information
to extract and rebuild both virtual and nonvirtual variable blocks; however
at the moment I don't understand the structure well enough to do it.

Here are the test programs:

--- test.c ---
inherit "/test_a";
inherit "/test_c";

--- test_a.c ---
string target_program = "test_a";

--- test_c.c ---
virtual inherit "/test_b";
string var2 = "test_c";

void create()
{
  replace_program("/test_c");
  set_var("content"); call_out( "write_var", 2 );
}

--- test_b.c ---
string var;

void set_var( string value )
{ var = value; write( "object="+object_name()+" [set_var()] var="+var+"\n" ); }

public void write_var()
{ write( "object="+object_name()+" [write_var()] var="+var+"\n" ); }

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