Option to print an array on one line

[AaronSteen]

I recently posted a question on StackOverflow about options in LLDB for printing C arrays on a single line. As it seems that it's not possible to do so without creating a custom command, Jim Ingham encouraged me to request that as an option here.

To summarize my issue, I'm looking for the ability to print an array's contents on a single line, instead of printing each value on its own line, as the parray command does. Basically, print it so that it looks like an array initializer. I have consulted extensively the LLDB Tutorial and attempted to use the type summary and synthetic child printing options, but as Jim noted, these do not work for arrays. For my personal workflow, I find vertical screen real estate to be very valuable, especially if I'm already using the majority of it to display some variables and 20 or so lines of code at each stop, so for small arrays I feel that an initializer-style print option makes a lot of sense.

[llvmbot]

@llvm/issue-subscribers-lldb

Author: None (friendlyman23)

I recently [posted a question](https://stackoverflow.com/questions/79266720/printing-c-arrays-passed-into-functions-in-lldb) on StackOverflow about options in LLDB for printing C arrays on a single line. As it seems that it's not possible to do so without creating a custom command, Jim Ingham encouraged me to request that as an option here.

To summarize my issue, I'm looking for the ability to print an array's contents on a single line, instead of printing each value on its own line, as the parray command does. Basically, print it so that it looks like an array initializer. I have consulted extensively the LLDB Tutorial and attempted to use the type summary and synthetic child printing options, but as Jim noted, these do not work for arrays. For my personal workflow, I find vertical screen real estate to be very valuable, especially if I'm already using the majority of it to display some variables and 20 or so lines of code at each stop, so for small arrays I feel that an initializer-style print option makes a lot of sense.

[DavidSpickett]

My guess is that if you could get from Python to to SetFlatOutput and SetAllowOnelinerMode in DumpValueObjectOptions, that would give you the value on a single line.

I think that is not possible right now, as I remember adding lldb/unittests/ValueObject/DumpValueObjectOptionsTests.cpp because I was not able to validate some similar options from Python either.

[jimingham]

I think this is a slightly more specific request than just to print vectors as one-liners. That already works for arrays that have fixed types, for instance:

(lldb) n
Process 26122 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x0000000100003f18 tryit`main at tryit.c:11
   8   	{
   9   	
   10  	  int array[] = {3, 0, 9, 4, 2};
-> 11  	  size_t size = sizeof(array) / sizeof(array[0]);
    	         ^
   12  	
   13  	  doSomething(array, size-1);
   14  	
Target 0: (tryit) stopped.
(lldb) v array
(int[5]) array = ([0] = 3, [1] = 0, [2] = 9, [3] = 4, [4] = 2)

So that is using the "print as one liner" compression (though the reporter might prefer not to have the index elements?)

The problem comes when you are trying to get an int * and a size to print as an int[size] using parray. The same array passed as an int */size renders as:

(lldb) parray `size` buf
(int *) $1 = 0x000000016fdfeed0 {
  [0] = 3
  [1] = 0
  [2] = 9
  [3] = 4
}

So what this is really asking for is that the return from parray (e.g. expr -Z <size> --) should also use the one-line display
if the user has turned that on.

[DavidSpickett]

if the user has turned that on.

How does the user do that, is it the "flat" option?

(lldb) help expression
<...>
       -F ( --flat )
            Display results in a flat format that uses expression paths for each variable or member.

Though this doesn't say that flat == a single line.