[
https://issues.apache.org/jira/browse/BCEL-202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14395240#comment-14395240
]
Daniel Stuber commented on BCEL-202:
------------------------------------
Some more work needs to be done for allowing users to adjust a method's
stack-map-table.
Some entry-types have their offset-delta stored in the frame-type. Thus
altering the offset-delta may need altering the frame-type, too. It can
therefore not be final any more. I also suggest to reduce the visibility of the
method to package-private.
StackMapTableEntry.java:
int calculateLength() {
if (frame_type >= Constants.SAME_FRAME && frame_type <=
Constants.SAME_FRAME_MAX) {
return 1;
} else if (frame_type >= Constants.SAME_LOCALS_1_STACK_ITEM_FRAME &&
frame_type <= Constants.SAME_LOCALS_1_STACK_ITEM_FRAME_MAX) {
return 1 + (types_of_stack_items[0].hasIndex() ? 3 : 1);
} else if (frame_type ==
Constants.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED) {
return 3 + (types_of_stack_items[0].hasIndex() ? 3 : 1);
} else if (frame_type >= Constants.CHOP_FRAME && frame_type <=
Constants.CHOP_FRAME_MAX) {
return 3;
} else if (frame_type == Constants.SAME_FRAME_EXTENDED) {
return 3;
} else if (frame_type >= Constants.APPEND_FRAME && frame_type <=
Constants.APPEND_FRAME_MAX) {
int len = 3;
for (int i = 0; i < types_of_locals.length; i++) {
len += types_of_locals[i].hasIndex() ? 3 : 1;
}
return len;
} else if (frame_type == Constants.FULL_FRAME) {
int len = 7;
for (int i = 0; i < types_of_locals.length; i++) {
len += types_of_locals[i].hasIndex() ? 3 : 1;
}
for (int i = 0; i < types_of_stack_items.length; i++) {
len += types_of_stack_items[i].hasIndex() ? 3 : 1;
}
return len;
} else {
/* Can't happen */
throw new ClassFormatException ("Invalid Stack map table tag: " +
frame_type);
}
}
Furthermore it might be necessary to completely replace a stack-map-entry with
another element resulting in a different length of the whole stack-map-table. I
do this as follows:
StackMapTable.java
public final void setStackMapTable( StackMapTableEntry[] map ) {
this.map = map;
int len = 2;
for (int i = 0; i < map.length; i++) {
len += map[i].calculateLength();
}
setLength(len);
}
This enforces a slight change in one constructor by directly setting the map
variable rather than calling setStackMapTable():
public StackMapTable(int name_index, int length, StackMapTableEntry[] map,
ConstantPool constant_pool) {
super(Constants.ATTR_STACK_MAP_TABLE, name_index, length,
constant_pool);
this.map = map;
}
> StackMapTableEntry.copy() needs to be deep; Improved support for StackMaps
> --------------------------------------------------------------------------
>
> Key: BCEL-202
> URL: https://issues.apache.org/jira/browse/BCEL-202
> Project: Commons BCEL
> Issue Type: Bug
> Reporter: Mark Roberts
> Attachments: stackmap.diff
>
>
> There are several ways a user can modify a Java class file that should cause
> BCEL to update the StackMaps automatically. Unfortunately, it does not.
> These additional methods at least allow users to take care of these issues
> for themselves.
> The patch also fixes a bug - StackMapTableEntry.copy() needs to be a deep
> copy to prevent StackMapTypes from being reused.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
