Displaying the array of structs ?

[sleeptightAnsiC]

Hi,

I see, there is a way to display the array made up with primitive data (Array Visualizer),
and also a way to display the fields of specific struct (Struct Visualizer),
but is it possible to display an array of structs ??

(note: this might be related to this feature request #142 )

For example, given the following C code with the breakpoint at return statement:

#include <stdlib.h>

struct CoordsData {
	int x;
	int y;
	int z;
};

struct CoordsArray {
	struct CoordsData *data;
	int num;
};

int main(void)
{
	struct CoordsArray arr;
	arr.num = 10;
	arr.data = malloc(sizeof(struct CoordsData) * arr.num);
	for (int i = 0; i < arr.num; ++i) {
		arr.data[i].x = i;
		arr.data[i].y = i + i;
		arr.data[i].z = i * i;
	}
	return 0;
}

I can try to display the values of arr.data with Array Visualizer, but without recognizing the members of struct CoordsData (x, y, z), like so:

or maybe even seperate 1-2 members by messing with offset and stride:

But this is still very slow to do and only possible in simple cases like this one.
Imagine that one must display something more complex.
Is there any way to do that right now?

[epasveer]

Hi! First, thanks for trying out Seer. Please keep comments and suggestions coming. :^)

Appologies for taking some time to get back to you. I was making sure I understood your comments. I think I do now.

but is it possible to display an array of structs

The short answer is no. At least not as Seer stands. (Have you seen other debuggers with the capability? If so, which one?)

In your example, you have a struct with an X, Y, and Z value. The ArrayVisualizer is really for a single array or two arrays. As the moment, it doesn't handle a third array. And I realize there's no way to "skip" the third array. For example, if you wanted to plot the X and Y points as a line, there's no way to skip the Z value. Thus, that image looks bad.

So I need some improvements.

• Need a way to "skip" some elements after an array.
• Add any number of arrays to the ArrayVisualizer. Not just a limit of 2.
• Add a 3D plot (X, Y, and Z) to visualize your use case.

only possible in simple cases like this one.

Yes, this is a crux. Your example is a simple structure. We also are lucky in that the values in the structure are contigious and have no "padding" between them. In a more complex example, what we did wouldn't actually work.

Another person has brought up the same issue.

I did some playing around. As it turns out, the underlying gdb supports something like &arr.data[5].x to be entered in the variable field. This means I might be able to support a minimalistic "scripting". Such as:

arr.data[$I].x     offset=0  stride=1
arr.data[$I].y     offset=1  stride=1
arr.data[$I].z     offset=2  stride=1

Or something like that.

Is there any way to do that right now?

So, sorry, not at the moment. But I'm willing to work on it.

Let me know what your thoughts are. I'm curious if you've seen other debuggers with the feature.

Thanks.

[sleeptightAnsiC]

Appologies for taking some time to get back to you.

No worries :^)

Have you seen other debuggers with the capability? If so, which one?

I haven't seen any that would work "out of the box" in this case BUT I've seen some that are able to evaluate the expression, display it in the table and create a plot/diagram out of it.

Given the code from my initial question, one can try to display the array content by evaluating *(arr.data)@(arr.num) like so:

(gdb) print *(arr.data)@(arr.num)
$1 = {{x = 0, y = 0, z = 0}, {x = 1, y = 2, z = 1}, {x = 2, y = 4, z = 4}, {x = 3, y = 6, z = 9}, {x = 4, y = 8, z = 16}, {x = 5, y = 10, z = 25}, {x = 6, y = 12, z = 36}, {x = 7, y = 14, z = 49}, {x = 8, y = 16, z = 64}, {x = 9, y = 18, z = 81}}

and this is how it looks in...

1. gnu ddd https://www.gnu.org/software/ddd/

2. gdbgui https://www.gdbgui.com/

One can also pass said expression into Seer's Variable/Register Info>Logger/Tracker
but this case was probably never meant to happen as those windows display data in a wrong way (known bug?)

Logger

Tracker

[sleeptightAnsiC]

Add a 3D plot (X, Y, and Z) to visualize your use case.

This isn't really my concern here. I'm more interested in displaying data as human-readable tables. This probably a bit easier to handle than plots as not every data type can be displayed as 2D/3D plot.

Also, one more thing worth mentioning (you probably already know this)
In GDB, there is a whole API for creating pretty printers.
Not surea if a front-end can make a good use of it though.
https://ftp.gnu.org/old-gnu/Manuals/gdb/html_node/gdb_57.html
https://docs.redhat.com/en/documentation/Red_Hat_Enterprise_Linux/6/html/developer_guide/debuggingprettyprinters#debuggingprettyprinters

[epasveer]

but this case was probably never meant to happen as those windows display data in a wrong way (known bug?)

Yeah, never thought of using the logger that way. I'm mildly surprised it does something mostly right. The Logger and Tracker should be identical output. I'll consider this a bug that the Tracker doesn't look like the Logger. Also, I think it's another bug that the "Name" column has a value of "{x". That's not right either.

[epasveer]

Overall, I think I know what you're asking for. I'll mull some things over. I'll reply (in time) with my game plan and you can comment on it.

Many thanks for your input!