[Bug c++/77489] New: Invalid mangling of static local variables

[Tom.Aernoudt at synopsys dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77489

            Bug ID: 77489
           Summary: Invalid mangling of static local variables
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Tom.Aernoudt at synopsys dot com
  Target Milestone: ---

Created attachment 39566
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39566&action=edit
testcase

According to the Itanium C++ ABI '5.1.6 Scope Encoding', the discriminator of
static local variables should be mangled as follows:

  <discriminator> := _ <non-negative number>      # when number < 10
                  := __ <non-negative number> _   # when number >= 10

But gcc always mangles it as follows:

  <discriminator> := _ <non-negative number>


The attached testcase can be used to reproduce the issue:

> g++ testcase.cc -o testcase.o -c
> nm testcase.o | grep localVar
0000000000000000 b _ZZ3foovE8localVar
0000000000000000 d _ZZ3foovE8localVar_0
0000000000000004 d _ZZ3foovE8localVar_1
0000000000000028 d _ZZ3foovE8localVar_10
000000000000002c d _ZZ3foovE8localVar_11
0000000000000008 d _ZZ3foovE8localVar_2
000000000000000c d _ZZ3foovE8localVar_3
0000000000000010 d _ZZ3foovE8localVar_4
0000000000000014 d _ZZ3foovE8localVar_5
0000000000000018 d _ZZ3foovE8localVar_6
000000000000001c d _ZZ3foovE8localVar_7
0000000000000020 d _ZZ3foovE8localVar_8
0000000000000024 d _ZZ3foovE8localVar_9

_ZZ3foovE8localVar_10 and _ZZ3foovE8localVar_11 should be mangled as
_ZZ3foovE8localVar__10_ and _ZZ3foovE8localVar__11_ according to the C++ ABI.

Tested with gcc 5.2:
> g++ -v
Using built-in specs.
COLLECT_GCC=/depot/gcc-5.2.0/bin/g++
COLLECT_LTO_WRAPPER=/depotbld/RHEL6.6/gcc-5.2.0/bin/../libexec/gcc/x86_64-redhat-linux/5.2.0/lto-wrapper
Target: x86_64-redhat-linux
Configured with: /remote/depotsrc/depotsrc/src/gcc-5.2.0/configure
--prefix=/depot/gcc-5.2.0 --enable-bootstrap --enable-threads=posix
--disable-checking --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-languages=c,c++,fortran
--disable-libgcj --with-cpu=generic --build=x86_64-redhat-linux
Thread model: posix
gcc version 5.2.0 (GCC) 


It looks like the master branch of gcc still has the issue, cfr
cp/mangle.c:1906:
  static void
  write_discriminator (const int discriminator)
  {
    /* If discriminator is zero, don't write anything.  Otherwise...  */
    if (discriminator > 0)
      {
        write_char ('_');
        write_unsigned_number (discriminator - 1);
      }
  }