[lldb-dev] lldb 11.0.0-rc2 different behavior then gdb.

[Jim Ingham via lldb-dev]

There isn’t a built-in summary formatter for two dimensional arrays of chars, but the type is matching the regex for the one-dimensional StringSummaryFormat, but that doesn’t actually know how to format two dimensional arrays of chars.  The type regex for StringSummaryFormat: 

char [[0-9]+]

We should refine this regex so it doesn’t catch up two dimensional strings.  We could also write a formatter for two-dimensional strings.  

Would you file bugs about those two issues with http://bugs.llvm.org? <http://bugs.llvm.org/?>  Thanks.

Note that user added formatters are scanned first and the match is granted to the first hit, so if you need this yourself, in the meantime you could write your own formatter and it should fire.

Jim


> On Oct 7, 2020, at 5:26 AM, Chirag Patel via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> 
> Hello all,
>  
> While debugging and printing struct with multi-dimensional char array, gdb successfully prints string while lldb bails out with only printing address.
> For simple C testcase,
>  
> struct b {
>         char i[2][4];
> };
>  
> int main() {
>         struct b z;
>         z.i[0][0] = 'F';
>         z.i[0][1] = 'O';
>         z.i[0][2] = 'O';
>         z.i[0][3] = 0;
>         z.i[1][0] = 'B';
>         z.i[1][1] = 'A';
>         z.i[1][2] = 'R';
>         z.i[1][3] = 0;
>         return 0;
> }
>  
> On gdb,
> Reading symbols from /home/chirag/a.out...done.
> (gdb) l
> 1       struct b {
> 2               char i[2][4];
> 3       };
> 4
> 5       int main() {
> 6               struct b z;
> 7               z.i[0][0] = 'F';
> 8               z.i[0][1] = 'O';
> 9               z.i[0][2] = 'O';
> 10              z.i[0][3] = 0;
> (gdb) l
> 11              z.i[1][0] = 'B';
> 12              z.i[1][1] = 'A';
> 13              z.i[1][2] = 'R';
> 14              z.i[1][3] = 0;
> 15              return 0;
> 16      }
> (gdb) b 15
> Breakpoint 1 at 0x400511: file Desktop/test/struct.c, line 15.
> (gdb) r
> Starting program: /home/chirag/./a.out
>  
> Breakpoint 1, main () at Desktop/test/struct.c:15
> 15              return 0;
> Missing separate debuginfos, use: debuginfo-install glibc-2.17-307.el7.1.x86_64
> (gdb) p z
> $1 = {i = {"FOO", "BAR"}}
> (gdb) q
> A debugging session is active.
>  
> While on lldb 11.0.0-rc2, (lldb) target create "/home/chirag/a.out"
> Current executable set to '/home/chirag/a.out' (x86_64).
> (lldb) b 15
> Breakpoint 1: where = a.out`main + 36 at struct.c:15, address = 0x0000000000400511
> (lldb) r
> Process 57100 launched: '/home/chirag/a.out' (x86_64)
> Process 57100 stopped
> * thread #1, name = 'a.out', stop reason = breakpoint 1.1
>     frame #0: 0x0000000000400511 a.out`main at struct.c:15
>    12           z.i[1][1] = 'A';
>    13           z.i[1][2] = 'R';
>    14           z.i[1][3] = 0;
> -> 15           return 0;
>    16   }
> (lldb) p z
> (b) $0 = (i = char [2][4] @ 0x0000000001fe3ca0)
> (lldb) q
>  
> It seems like the type summary formatter is failing? Or is it the intended behaviour?.
>  
> Thanks and Regards,
> Chirag Patel.
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