lldb: one line output for `print` and `display`

Question

For example, with the source code main.c :

#include <stdio.h>

int main()
{
    int a[10] = {0,1,2,3,4,5,6,7,8,9};
    int b = 2;
    printf("line 7\n");
    printf("line 8\n");
    return 0;
}

With the LLDB debugger, print a produce:

(int [10]) $0 = {
  [0] = 0
  [1] = 1
  [2] = 2
  [3] = 3
  [4] = 4
  [5] = 5
  [6] = 6
  [7] = 7
  [8] = 8
  [9] = 9
}

question 0: How can I get a compact printing on one line for print , like with GDB :

$1 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

With the LLDB debugger, display a and display b produce:

- Hook 1 (expr -- a)
(int [10]) $0 = {
  [0] = 0
  [1] = 1
  [2] = 2
  [3] = 3
  [4] = 4
  [5] = 5
  [6] = 6
  [7] = 7
  [8] = 8
  [9] = 9
}

- Hook 2 (expr -- b)
(int) $1 = 2

question 1: How can I get a compact printing on two lines for display , like with GDB :

2: b = 2
1: a = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

Answer 1

by default the decision of what types do and do not get “one line” printing is hardcoded in FormatManager::ShouldPrintAsOneLiner

The only setting that users can tweak with regard to that is

(lldb) settings show auto-one-line-summaries
auto-one-line-summaries (boolean) = true

which acts as a global kill-switch for the feature (true means “allow”)

A quick fix for your problem is to manually add a summary for all int arrays, thusly:

(lldb) type summary add -x "int \[[0-9]+]" -c

That is saying, for all types whose names match the regular expression int [ followed by one ore more digits followed by a ], then force one-line formatting

With that, I get

(lldb) fr var x
(int [10]) x = ([0] = 0, [1] = 1, [2] = 2, [3] = 3, [4] = 4, [5] = 5, [6] = 6, [7] = 7, [8] = 8, [9] = 9)
(lldb) expr x
(int [10]) $2 = ([0] = 0, [1] = 1, [2] = 2, [3] = 3, [4] = 4, [5] = 5, [6] = 6, [7] = 7, [8] = 8, [9] = 9)

With all of that said, I think you are on an older version of LLDB

On a fairly recent build of the debugger, I get one-line display even without customizing the formatting:

(lldb) expr x
(int [10]) $0 = ([0] = 0, [1] = 1, [2] = 2, [3] = 3, [4] = 4, [5] = 5, [6] = 6, [7] = 7, [8] = 8, [9] = 9)