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February/March 2016 GNU Toolchain Update

Hi Guys,

  There are lots of new features to report about this time, so here

  * GDB 7.11 has been released.

    This release brings many new features and enhancements, including:

    + Per-inferior thread numbers.
      (thread numbers are now per inferior instead of being global).

    + GDB now allows users to specify breakpoint locations using a
      more explicit syntax (named "explicit location").

    + When hitting a breakpoint or receiving a signal while debugging
      a multi-threaded program, the debugger now shows which thread
      triggered the event.

    + Record btrace now supports non-stop mode.

    + Various improvements on AArch64 GNU/Linux:
       - Multi-architecture debugging support.
       - Displaced stepping.
       - Tracepoint support added in GDBserver.

    + Kernel-based threads support on FreeBSD.

  * Not to be outdone the GLIBC team have also announced a major new
    release - version 2.23.  Full details can be found here:

    But here are some highlights:
      + Unicode 8.0.0 Support

      + getaddrinfo now detects certain invalid responses on an internal
        netlink socket.

      + A defect in the malloc implementation could result in the
        unnecessary serialization of memory allocation requests across 
        threads.  The defect is now corrected.  Users should see a
        substantial increase in the concurrent throughput of allocation
        requests for applications which used to trigger this bug.
        Affected applications typically create and destroy threads

      + There is now a --disable-timezone-tools configure option for
        disabling the building and installing of the timezone related
        utilities (zic, zdump, and tzselect).

      + The obsolete header <regexp.h> has been removed.  Programs that
        require this header must be updated to use <regex.h> instead.

      + Optimized string, wcsmbs and memory functions for IBM z13.

  Meanwhile in GCC land, work on getting the code ready for the GCC 6
  branch continues at a furious pace.  Some new features have made it
  in over the last couple of months however, and here are the details:
  * Initial support for the C++ Extensions for Concepts Technical
    Specification, ISO 19217 (2015), has been added to G++.  This allows
    code like this:

      template <class T> concept bool Addable = requires (T t) { t + t; };
      template <Addable T> T add (T a, T b) { return a + b; }

  * The new GCC warning option "-Wnonnull-compare" can be used to
    generate a warning when comparing a variable with the "nonnull"
    attribute against null.

  * The -Wunused-const-variable option has been extended.  A setting of
    -Wunused-const-variable=1 only generates warnings about unused
    static const variables in the main compilation unit, and not in
    headers.  A setting of -Wunused-const-variable=2 also warns about
    unused static const variables in non-system header files.  This
    second setting corresponds to the old -Wunused-const-variable
    behaviour but it must now be explicitly requested since in C++ it
    is not an error and in C it might be hard to clean up all headers
  * The -fshort-double command line option has now been deprecated.

  * The ARC backend of GCC now supports a -mfpu= command line option to
    select the type of floating point operations that can be used.

  * A GCC enhancement was made a while ago, but I totally failed to
    report on it.  Fortunately reader David Wolfherd pointed this out
    to me, so here is the news:
    The inline assembler feature in GCC now has the ability to specify
    the flags set in the condition code register as part of the output
    of the asm.  This helps the compiler as it can now use that
    information to improve the code that it generates after the inline

    For more details see:


  There are also some changes to report in the binutils:

   * The binutils for ELF based targets can now handle commons as either
     the STT_COMMON or STT_OBJECT type.  A configure time option can
     select the default, and command line options to ld, gas and objcopy
     can be used to specify exactly which type should be used.
   * The LD linker now supports a couple of new features:

     + The command line option "-z noreloc-overflow" in the x86-64 ELF
       linker to disable relocation overflow check.
     + The command line options "-z nodynamic-undefined-weak" in the x86
       ELF linker can be used to avoid generating dynamic relocations
       against undefined weak symbols in executable.

   * The GAS assembler can now set ELF section flags and types via
     numeric values.  This allows extra or unusual bits in these fields
     to be set.

   * GAS for x86 targets now also supports a command line option of
     "-mfence-as-lock-add=yes" which encodes the lfence, mfence and
     sfence opcodes as "lock addl $0x0, (%[re]sp)".
   * The ARC port of GAS now supports assembly-time relaxation.

  And last, bit not least, there is a new feature in newlib as well:

   * Newlib now supports the clog10 and clog10f math functions.

  That's it for this report.  Back in two months time.  Meanwhile I have
  a minor plug to offer: some other Red Hat developers have written
  blogs about new features that will be in the upcoming GCC 6 release.
  So if you are interested in what will happen, please see:



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