[Valgrind-users] Valgrind-3.21.0.RC2 is available for testing

[Mark W. <ma...@kl...>]

An RC2 tarball for 3.21.0 is now available at
https://sourceware.org/pub/valgrind/valgrind-3.21.0.RC2.tar.bz2
(md5sum = f33407fdffbfa78f5014781cc92297cf)
(sha1sum = c520ee0c28d9e20d28aa25d05ce2525c39a69135)
https://sourceware.org/pub/valgrind/valgrind-3.21.0.RC2.tar.bz2.asc

Please give it a try in configurations that are important for you and
report any problems you have, either on this mailing list, or
(preferably) via our bug tracker at
https://bugs.kde.org/enter_bug.cgi?product=valgrind

Please check the NEWS entry below for new features that could use some
extra testing. Note that there has also been a dhat extension which
hasn't yet been added to NEWS.

There is now a a client request for DHAT to mark memory to be
histogrammed:
https://bugs.kde.org/464103
https://snapshots.sourceware.org/valgrind/trunk/latest/html/dh-manual.html#dh-access-counts

If nothing critical emerges, a final release will happen on
Friday 28 April.

* ==================== CORE CHANGES ===================

* When GDB is used to debug a program running under valgrind using
  the valgrind gdbserver, GDB will automatically load some
  python code provided in valgrind defining GDB front end commands
  corresponding to the valgrind monitor commands.
  These GDB front end commands accept the same format as
  the monitor commands directly sent to the Valgrind gdbserver.
  These GDB front end commands provide a better integration
  in the GDB command line interface, so as to use for example
  GDB auto-completion, command specific help, searching for
  a command or command help matching a regexp, ...
  For relevant monitor commands, GDB will evaluate arguments
  to make the use of monitor commands easier.
  For example, instead of having to print the address of a variable
  to pass it to a subsequent monitor command, the GDB front end
  command will evaluate the address argument. It is for example
  possible to do:
    (gdb) memcheck who_point_at &some_struct sizeof(some_struct)
  instead of:
    (gdb) p &some_struct
    $2 = (some_struct_type *) 0x1130a0 <some_struct>
    (gdb) p sizeof(some_struct)
    $3 = 40
    (gdb) monitor who_point_at 0x1130a0 40

* The vgdb utility now supports extended-remote protocol when
  invoked with --multi. In this mode the GDB run command is
  supported. Which means you don't need to run gdb and valgrind
  from different terminals. So for example to start you program
  in gdb and run it under valgrind you can do:
  $ gdb prog
  (gdb) set remote exec-file prog
  (gdb) set sysroot /
  (gdb) target extended-remote | vgdb --multi
  (gdb) start

* The behaviour of realloc with a size of zero can now
  be changed for tools that intercept malloc. Those
  tools are memcheck, helgrind, drd, massif and dhat.
  Realloc implementations generally do one of two things
     - free the memory like free() and return NULL
       (GNU libc and ptmalloc).
     - either free the memory and then allocate a
       minumum siized block or just return the
       original pointer. Return NULL if the
       allocation of the minimum sized block fails
       (jemalloc, musl, snmalloc, Solaris, macOS).
  When Valgrind is configured and built it will
  try to match the OS and libc behaviour. However
  if you are using a non-default library to replace
  malloc and family (e.g., musl on a glibc Linux or
  tcmalloc on FreeBSD) then you can use a command line
  option to change the behaviour of Valgrind:
    --realloc-zero-bytes-frees=yes|no [yes on Linux glibc, no otherwise]

* ================== PLATFORM CHANGES =================

* Make the address space limit on FreeBSD amd64 128Gbytes
  (the same as Linux and Solaris, it was 32Gbytes)

* ==================== TOOL CHANGES ===================

* Memcheck:
  - When doing a delta leak_search, it is now possible to only
    output the new loss records compared to the previous leak search.
    This is available in the memcheck monitor command 'leak_search'
    by specifying the "new" keyword or in your program by using
    the client request VALGRIND_DO_NEW_LEAK_CHECK.
    Whenever a "delta" leak search is done (i.e. when specifying
    "new" or "increased" or "changed" in the monitor command),
    the new loss records have a "new" marker.
  - Valgrind now contains python code that defines GDB memcheck
    front end monitor commands. See CORE CHANGES.
  - Performs checks for the use of realloc with a size of zero.
    This is non-portable and a source of errors. If memcheck
    detects such a usage it will generate an error
      realloc() with size 0
    followed by the usual callstacks.
    A switch has been added to allow this to be turned off:
      --show-realloc-size-zero=yes|no [yes]

* Helgrind:
  - The option ---history-backtrace-size=<number> allows to configure
    the number of entries to record in the stack traces of "old"
    accesses. Previously, this number was hardcoded to 8.
  - Valgrind now contains python code that defines GDB helgrind
    front end monitor commands. See CORE CHANGES.

* Cachegrind:
  - `--cache-sim=no` is now the default. The cache simulation is old and
    unlikely to match any real modern machine. This means only the `Ir`
    event are gathered by default, but that is by far the most useful
    event.
  - `cg_annotate`, `cg_diff`, and `cg_merge` have been rewritten in
    Python. As a result, they all have more flexible command line
    argument handling, e.g. supporting `--show-percs` and
    `--no-show-percs` forms as well as the existing `--show-percs=yes`
    and `--show-percs=no`.
  - `cg_annotate` has some functional changes.
    - It's much faster, e.g. 3-4x on common cases.
    - It now supports diffing (with `--diff`, `--mod-filename`, and
      `--mod-funcname`) and merging (by passing multiple data files).
    - It now provides more information at the file and function level.
      There are now "File:function" and "Function:file" sections. These
      are very useful for programs that use inlining a lot.
    - Support for user-annotated files and the `-I`/`--include` option
      has been removed, because it was of little use and blocked other
      improvements.
    - The `--auto` option is renamed `--annotate`, though the old
      `--auto=yes`/`--auto=no` forms are still supported.
  - `cg_diff` and `cg_merge` are now deprecated, because `cg_annotate`
    now does a better job of diffing and merging.
  - The Cachegrind output file format has changed very slightly, but in
    ways nobody is likely to notice.

* Callgrind:
  - Valgrind now contains python code that defines GDB callgrind
    front end monitor commands. See CORE CHANGES.

* Massif:
  - Valgrind now contains python code that defines GDB massif
    front end monitor commands. See CORE CHANGES.