Boost C++ Libraries: Ticket #3869: Unconditional call to memset in value_initialized()

attachment set

niels_dekker — Thu, 28 Jan 2010 14:49:39 GMT

attachment → config_compiler.patch

Adds BOOST_VALUE_INITIALIZATION_NEEDS_MEMSET to trunk/boost/config/compiler

niels_dekker — Thu, 28 Jan 2010 14:53:04 GMT

Fernando (the author of value_init) mailed me that it's okay to him if I add an #ifdef to utility/value_init.hpp:

  #ifdef BOOST_VALUE_INITIALIZATION_NEEDS_MEMSET
       std::memset(&x, 0, sizeof(x));
  #endif

But therefor, this macro needs to be defined in <boost/config/compiler/...>, for the relevant compiler versions. Hereby I have attached my proposed additions to the trunk version of boost/config/compiler: config_compiler.patch Please check if it's okay.

John Maddock — Fri, 29 Jan 2010 15:27:36 GMT

The patch is OK as far as it goes, but we should have documentation and tests for each new macro, please see: http://www.boost.org/doc/libs/1_41_0/libs/config/doc/html/boost_config/guidelines_for_boost_authors.html#boost_config.guidelines_for_boost_authors.adding_new_defect_macros

Thanks, John.

niels_dekker — Fri, 29 Jan 2010 17:14:57 GMT

Thanks, John. I read that there's a BOOST_NO_SOMETHING naming convention. So now I'm considering to name the macro BOOST_NO_PROPER_VALUE_INITIALIZATION_FOR_ALL_TYPES. (Instead of BOOST_VALUE_INITIALIZATION_NEEDS_MEMSET.) So that the unit test should show that compilers that have this macro defined do indeed do an improper value-initialization, for at least one type.

I'll have a closer look later...

niels_dekker — Sun, 04 Apr 2010 14:14:10 GMT

Hereby I have just added a new patch for boost/config (to be applied to the trunk): https://svn.boost.org/trac/boost/attachment/ticket/3869/no_complete_value_initialization.patch It adds a new macro, BOOST_NO_COMPLETE_VALUE_INITIALIZATION, and includes documentation and tests. Please tell me what you think.

attachment set

niels_dekker — Wed, 07 Apr 2010 10:11:56 GMT

attachment → no_complete_value_initialization.patch

New proposed patch, adding BOOST_NO_COMPLETE_VALUE_INITIALIZATION. Replaces the old config_compiler.patch (Update: removed Boost.Test dependency, as suggested by John Maddock.)

attachment set

niels_dekker — Sun, 16 May 2010 11:39:26 GMT

attachment → value_init_workaround.patch

Made memset call conditional, based on BOOST_NO_COMPLETE_VALUE_INITIALIZATION

niels_dekker — Sun, 16 May 2010 12:01:49 GMT

The value_init_workaround.patch I just attached should resolve this ticket. It assumes that the defect macro BOOST_NO_COMPLETE_VALUE_INITIALIZATION is defined for those compilers that need it (ticket #4080). Note that it adds an extra macro, BOOST_DETAIL_VALUE_INIT_WORKAROUND (defined as either 0 or 1), which controls whether the memset workaround is applied. This macro is merely intended as an implementation detail: I would like to have an extra test which toggles the value of the macro, in order to check if the workaround is both effective and necessary.

niels_dekker — Sun, 30 May 2010 09:19:12 GMT

(In [62307]) Made memset call in value_init conditional, see #3869. Updated the section "compiler issues" of its documentation.

attachment set

niels_dekker — Sun, 30 May 2010 12:47:24 GMT

attachment → value_init_workaround_test.cpp

niels_dekker — Wed, 16 Jun 2010 08:45:46 GMT

(In [63014]) Added value_init_workaround_test, reviewed by Fernando Cacciola, see #3869

niels_dekker — Sun, 04 Jul 2010 21:56:49 GMT

(In [63638]) Merged value_init fixes (extra tests + documentation) from trunk, see #3472, #3869.

viboes — Sun, 03 Jun 2012 20:31:22 GMT

Is there something else to be added? If not, could you close the issue?

status changed; resolution set

niels_dekker — Mon, 04 Jun 2012 11:55:45 GMT

status new → closed
resolution → fixed

Closed, as suggested by Vicente (viboes).