Heap Peek

Heap Peek is a debug feature available since LabVIEW 14. It allows to view internal data structures created for all loaded VI files, including Front Panel Heap and Block Diagram Heap. The feature is intended for use by LV R&D, though users may in some cases be instructed by LV Support to check something there.

Enabling Heap Peek

The Heap Peek keyboard shortcut is by default disabled in fresh installations of LabVIEW. To enable it:

Close LabVIEW
Put the key "LVdebugKeys=True" in your LabVIEW configuration file

Then, to trigger the Heap Peek window:

Open your VI
Press CTRL+SHIFT+D+H. On Mac, use the command key instead of CTRL. This will open the Heap Peek window.

Using Heap Peek

The window is divided into 5 sections:

Loaded Container Files are in top-left,
Heap View is top-right,
Structure selection for info pane in middle-left,
Toolbar at the middle,
Information pane is at base.

The first section, as for usage flow, is top-left one. Start there, by left clicking to select the specific file and specific heap you want to look at. When the heap is selected, you can display many details on it by clicking rows of either top-right or middle section. These details will show at base, in Information pane.

Note: Heap Peek does not have any ability to change the objects. It is display information only.

Loaded Container Files list

The list is divided into Contexts. In each of these, you can see memory location of the item (within LabVIEW process memory), and entries marked BDHP or FPHP.

BDHP is Block Diagram Heap
FPHP is Front Panel Heap

Note: There are VIs in LV that are not real VIs (for example, a pseudo VI that is created to represent a Call By Reference to another application instance on another machine), and attempting to do Find to jump to their components can cause problems because those VIs never expect to actually draw themselves.

Heap View

Heaps are displayed in a flattened form, not in its full tree-like glory. Part of the entries show properties of the whole pane, and the rest is controls, indicators and other elements added to the pane.

The view for FPHP reveals that controls and indicators are composed of several parts - ie. Numeric controls consist of: Label, Frame, Up/Down buttons, Edit field, Radix and Annex.

Note: To learn more about LV Heaps, consider exporting a few to XML, and looking at them there. The flat list visible in Heap View will be very helpful when you understand them, but it's not the best way to acquire that understanding.

Structure selection

Here you can select one of the structures within VI files other than FPHP/BDHP. These are per-file, not per-heap - so you won't find any difference in them if you select different part of the same file in Loaded Container Files list.

The selectable options are:

VI Fields - lists values of many common settings and flags of the VI file
DS Fields - lists Data Space properties, including Table of QEs and Table of TMEs
OH Fields
Stats - statistics for objects used within Heaps
Link Info - content of all LinkObj lists
Names In Memory
IL Code Stream - Prints Intermediate Language Code used during code compilation process
Code Disassembly - Prints assembly generated by the compiler for given VI file
Transform Metrics
UDClass Info
Full OMUDClassPtr List
Available Implementers

Toolbar

The toolbar consists of several fields.

Next/prev buttons
Currently selected item name text
U button
F button - Click on it to find the object selected in Heap View. LabVIEW will switch to the block diagram or front panel and select related object.
UO button

Note: A previous author said that few developers really know the capacities of heap peek. This is true... it's a debugging tool, and it gets hacked up to debug whatever anyone needs to debug.