[Bug 1577891] Re: Placement new destructor call optimized out

[Matthias Klose]

** Bug watch added: GCC Bugzilla #77983
   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77983

** Also affects: gcc via
   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77983
   Importance: Unknown
       Status: Unknown

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Title:
  Placement new destructor call optimized out

Status in gcc:
  Unknown
Status in gcc-5 package in Ubuntu:
  Confirmed

Bug description:
  We have a template class that we are using with placement new.  Code works fine in g++ (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4,
  however in g++ (Ubuntu 5.3.1-14ubuntu2) 5.3.1 20160413, the destructor call is optimized out, even though we explicitly call it.  

  I have attached sample code (reduced down from our project) to show the issue.  If we add a NON-POD data type, everything works
  fine... this however is not an option for our project, as in our environment this is normally a packed class, though the example fails
  either way.

  
  This works:

  g++ -O0 -g -ggdb test.cpp -o test0 
  ./test0
  Before:000102030405060708090a0b0c0d0e0f10111213
  After :0000000000000000000000000000000000000000

  
  These do not:

  g++ -O1 -g -ggdb test.cpp -o test1
  g++ -O2 -g -ggdb test.cpp -o test2
  g++ -O3 -g -ggdb test.cpp -o test3
  ./test1
  Before:000102030405060708090a0b0c0d0e0f10111213
  After :000102030405060708090a0b0c0d0e0f10111213

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