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On 2024-03-30T00:23:30+00:00 Zixing Liu wrote:

Created attachment 15447
Minimal reproducible example (D source code)

Hi there,

I have discovered a D class type resolution regression since GDB 10 (it
was working properly in GDB 9).

Please find the reproducer in the file attached. You can compile the
source code using either GDC or LDC2 (both can reproduce this issue):

gdc -g -O0 t.d -o t

To reproduce the bug, set the breakpoint to t.d:10 and examine the `i`
global variable (using `p t.i`). GDB will then complain that "'t.i' has
unknown type; cast it to its declared type."

I found a workaround to this problem by using `p (uv*)_D1t1iCQf2uv`, but
obviously, this is non-ideal: the developer may not know the mangled
variable name easily.

Since this looks like a regression, I did a simple `git bisect` that led
me to this commit: https://sourceware.org/git/?p=binutils-
gdb.git;a=commit;h=727b7b1864973c2645a554727afd0eaf1303673a. I am unsure
how demangle changes could affect the type resolution (maybe it's
because GDB got confused about which entity to decode?)

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/2059856/comments/0

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On 2024-03-30T19:30:45+00:00 Tromey-b wrote:

Computing the "physname" decides that the symbol should be named:

(top-gdb) p physname
$37 = 0x2c70490 "_D1t1iCQf2uv"

... which is plainly wrong.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/2059856/comments/1

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On 2024-03-30T19:36:27+00:00 Tromey-b wrote:

Ok, so while gdb's symbol reader is still really wrong here --
this physname stuff is pretty broken -- the root cause of this
particular bug is also that libiberty does not auto-demangle
D symbols.

You can see this on the command line:

prentzel. c++filt  _D1t1iCQf2uv
_D1t1iCQf2uv
prentzel. c++filt -s dlang  _D1t1iCQf2uv
t.i

To my eye this seems to be an oversight in cplus-dem.c,
where the D code follows some earlier code; but perhaps
the author didn't realize that the reason the Ada
code does not check AUTO_DEMANGLING is that the
Ada encoding isn't unambiguous in the way the D encoding is.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/2059856/comments/2

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On 2024-03-30T19:49:00+00:00 Tromey-b wrote:

Testing a patch.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/2059856/comments/3

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On 2024-03-30T20:10:51+00:00 Tromey-b wrote:

https://sourceware.org/pipermail/gdb-patches/2024-March/207686.html

Reply at:
https://bugs.launchpad.net/ubuntu/+source/gdb/+bug/2059856/comments/4


** Changed in: gdb
       Status: Unknown => Confirmed

** Changed in: gdb
   Importance: Unknown => Medium

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https://bugs.launchpad.net/bugs/2059856

Title:
  gdb 10.0 fails to examine any global variables in D programs

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