[Bug libstdc++/96345] New: __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

Bug ID: 96345
   Summary: __cxa demangle fails to demangle a very long string
   Product: gcc
   Version: 10.1.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: hededrk at gmail dot com
  Target Milestone: ---

I found this bug because one of my tests started to fail (not sure when it
started to fail because I've set up CI only yesterday). I assume this is a bug
because GCC is able to produce such names.

Steps to reproduce:
1. compile attached file
g++ -c cxa_demangle_fail.cpp

2. obtain mangled name with nm
nm cxa_demangle_fail.o

3. pass that name into abi::__cxa_demangle
auto name   = /*long string*/;
size_t size = 1024;
auto memory = static_cast(malloc(size));

int status;
auto demangled = abi::__cxa_demangle(name, memory, &size, &status);

Result: __cxa_demangle fails with code -2.

[Bug libstdc++/96345] __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

--- Comment #1 from V  ---
Created attachment 48936
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48936&action=edit
failing example

[Bug libstdc++/96345] __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

--- Comment #2 from V  ---
Created attachment 48937
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=48937&action=edit
function with name that __cxa_demangle rejects

[Bug libstdc++/96345] __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

--- Comment #4 from V  ---
No, c++filt also does not demangle it.

[Bug libstdc++/96345] __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

--- Comment #5 from V  ---
(In reply to Andrew Pinski from comment #3)
> Does c++filt demangle it?

I've fed output of nm into c++filt and this function came out mangled, while
others were demangled.

[Bug demangler/96345] __cxa demangle fails to demangle a very long string

[hededrk at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96345

V  changed:

   What|Removed |Added

Version|10.1.0  |12.1.1
   Host||x86_64
 Target||x86_64

--- Comment #6 from V  ---
Still fails as of GCC 12.1.

I've shortened the input string, it fails with names longer than 999
characters.