[Bug gdb/18165] New: incorrect evaluation of copy constructor on return statement

["matei at cs dot toronto.edu" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=18165

            Bug ID: 18165
           Summary: incorrect evaluation of copy constructor on return
                    statement
           Product: gdb
           Version: 7.9
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: matei at cs dot toronto.edu

Created attachment 8207
  --> https://sourceware.org/bugzilla/attachment.cgi?id=8207&action=edit
demonstrates bug

GDB incorrectly executes a copy constructor at the end of a function which
returns its result by value. This bug is new in 7.9, I checked 7.7.1 and 7.8.2
and they both work fine.

Compile with:
g++ -std=c++11 -O0 -g3 -ggdb -Wall -Wextra -pedantic a.cpp -o a

I tried:
gcc-4.9.2 and clang-3.5.0; same result.

Run gdb as follows:
gdb -q -ex 'file a' -ex 'b done' -ex 'r' -ex 'p _a' -ex 'p _a2' -ex 'p a()' -ex
q

With gdb-7.9, I see:
$1 = {_val = 15}
$2 = {_val = 15}
$3 = {_val = 0}

With gdb-7.8.2, I see:
$1 = {_val = 15}
$2 = {_val = 15}
$3 = {_val = 15}

Strangely enough, I noticed that commenting out the "= default" statement makes
the bug disappear. But having it there is valid code, so it should work.

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