[Bug gdb/30315] GDB not showing variable that is supposed to be there

["ssbssa at sourceware dot org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=30315

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ssbssa at sourceware dot org

--- Comment #2 from Hannes Domani <ssbssa at sourceware dot org> ---
I've debugged it to this location of read_lexical_block_scope in dwarf2/read.c:
```
    case PC_BOUNDS_NOT_PRESENT:
      /* DW_TAG_lexical_block has no attributes, process its children as if
         there was no wrapping by that DW_TAG_lexical_block.
         GCC does no longer produces such DWARF since GCC r224161.  */
```
The inner { int i; } block is optimized away, and apparently gcc produces
this kind of block here in this case.
Which means gdb moves up the i variable to the for{} block, and that's why
it's found by print.
As a test I've just put a return in this case block, then gdb found the
correct i also in this location:
```
(gdb) n
12          b = 0;
(gdb) p i
$2 = 4
(gdb) info addr i
Symbol "i" is multi-location:
  Base address 0x140001609  Range 0x13f2e1609-0x13f2e1609: the constant 0
  Range 0x13f2e1609-0x13f2e1609: the constant 1
  Range 0x13f2e1609-0x13f2e1609: the constant 2
  Range 0x13f2e1609-0x13f2e1609: the constant 3
  Range 0x13f2e1609-0x13f2e161c: the constant 4
```

I'm not sure what the correct solution here is.

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