[lldb-dev] Force format for frame variable using type summary is not working as expected.

[Jim Ingham via lldb-dev]

The way lldb works, char[] has a type summary that does two things, 1) presents the contents as a C-string, and 2) suppresses the actual printing of the elements.  If it hadn't done (2) then you would have seen the elements formatted as a vector of char's with the format you specified.  OTOH (2) is very desirable when you have a char[100].  You don't want to see the string then many individual char elements below it.

If you want to print the raw values of something that has a child suppressing summary, currently you "--raw -format x".

It would make sense to pass the summary provider the requested format.  SBValue has a GetFormat option, so if the format was properly set on the SBValue before it's passed to the summary provider, that would work already.  Then it's up to the summary providers to do whatever seems appropriate with that format.  

We could also just suppress the summary and go back to the raw view if the format has been set by the user.  Though in that case you would see:

(lldb) fr v -f x arr
(char [13]) arr = {
  [0] = 0x48
  [1] = 0x65
  [2] = 0x6c
  [3] = 0x6c
  [4] = 0x6f
  [5] = 0x20
  [6] = 0x57
  [7] = 0x6f
  [8] = 0x72
  [9] = 0x6c
  [10] = 0x64
  [11] = 0x21
  [12] = 0x00
}

since that's how arrays get printed in lldb.

Jim


> On Jan 8, 2020, at 12:09 AM, Chirag Patel via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> 
> Hello,
>  
> I am trying to debug a simple c program,
> int main() {
>     char arr[] = "Hello World!";
> }
>  
> On gdb, while printing variable content with force formatting,
> (gdb) l
> 1       int main() {
> 2               char arr[] = "Hello World!";
> 3       }
> (gdb) b 3
> Breakpoint 2 at 0x40050a: file string.c, line 3.
> (gdb) r
> Starting program: /home/chirag/Desktop/test/./a.out
>  
> Breakpoint 2, main () at string.c:3
> 3       }
> (gdb) p arr
> $4 = "Hello World!"
> (gdb) p /d arr
> $5 = {72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100, 33, 0}
> (gdb) p /x arr
> $6 = {0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x20, 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21, 0x0}
> (gdb)
>  
>  
> While on lldb, 
> (lldb) l
>    1    int main() {
>    2            char arr[] = "Hello World!";
>   3    }
> (lldb) b 3
> Breakpoint 1: where = a.out`main + 29 at string.c:3, address = 0x000000000040050a
> (lldb) r
> Process 59671 launched: '/home/chirag/Desktop/test/a.out' (x86_64)
> Process 59671 stopped
> * thread #1, name = 'a.out', stop reason = breakpoint 1.1
>     frame #0: 0x000000000040050a a.out`main at string.c:3
>    1    int main() {
>    2            char arr[] = "Hello World!";
> -> 3    }
> (lldb) fr v arr
> (char [13]) arr = "Hello World!"
> (lldb) fr v arr -f d
> (char [13]) arr = "Hello World!"
> (lldb) fr v arr -f x
> (char [13]) arr = "Hello World!"
> (lldb)
>  
> It seems like lldb type summary is completely ignoring the force format option, is it a bug or it is intended?
>  
> Regards,
>  
> Chirag Patel
> Software Engineer | Raincode Labs India
> Tel: (+91) 080 41159811
> Mob: (+91) 9049336744
> www.raincodelabs.com
> <image003.png>
>  
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