initial

10 files changed, 910 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..851644a
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+/tmp
+*.o
+*.so
+/pkg
+/*.gem
diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000..d159169
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable.  However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/MANIFEST b/MANIFEST
new file mode 100644
index 0000000..fe097e1
--- /dev/null
+++ b/MANIFEST
@@ -0,0 +1,10 @@
+.gitignore
+COPYING
+MANIFEST
+README
+Rakefile
+bin/mwrap
+ext/mwrap/extconf.rb
+ext/mwrap/mwrap.c
+mwrap.gemspec
+test/test_mwrap.rb
diff --git a/README b/README
new file mode 100644
index 0000000..c6d45d0
--- /dev/null
+++ b/README
@@ -0,0 +1,58 @@
+= mwrap - LD_PRELOAD malloc wrapper + line stats for Ruby
+
+Wraps all malloc, calloc, and realloc calls to trace the Ruby source
+location of such calls and bytes allocated at each callsite.  This
+functionality may change incompatibly or be expanded in the future.
+
+This is useful for finding malloc hotspots in Ruby code.  It does
+not track allocation lifetimes, or frees, however.
+
+Only supports Ruby trunk (2.6.0dev+) a few platforms:
+
+* GNU/Linux
+* FreeBSD 11
+
+== Usage
+
+It works as an LD_PRELOAD and supplies a mwrap RubyGem executable to
+improve ease-of-use.  You can set dump_fd: in the MWRAP environment
+variable to dump the results to a certain file descriptor at exit:
+
+        MWRAP=dump_fd:2 mwrap RUBY_COMMAND
+
+You may also set dump_path to append to a log file:
+
+        MWRAP=dump_path:/path/to/log mwrap RUBY_COMMAND
+
+You may also `require 'mwrap'' in your Ruby code and use
+Mwrap.dump and Mwrap.clear.
+
+== Known problems
+
+* 32-bit machines are prone to overflow (WONTFIX)
+
+* Allocations outside of GVL are not tracked (TODO)
+
+== Mail archives and list:
+
+        https://80x24.org/mwrap-public/
+        nntp://80x24.org/inbox.comp.lang.ruby.mwrap
+
+No subscription will ever be required to post, but HTML mail
+will be rejected:
+
+                mwrap-public@80x24.org
+
+== Hacking
+
+        git clone https://80x24.org/mwrap.git
+
+Send all patches and pull requests (use "git request-pull" to format) to
+the mailing list.  We do not use centralized or proprietary messaging
+systems.
+
+== License
+
+GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+
+Note: we may depend on 3rd-party LGPL/GPL libraries in future releases
diff --git a/Rakefile b/Rakefile
new file mode 100644
index 0000000..50bfa89
--- /dev/null
+++ b/Rakefile
@@ -0,0 +1,16 @@
+# Copyright (C) 2018 mwrap hackers <mwrap-public@80x24.org>
+# License: GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+require 'rake/testtask'
+begin
+  require 'rake/extensiontask'
+  Rake::ExtensionTask.new('mwrap')
+rescue LoadError
+  warn 'rake-compiler not available, cross compiling disabled'
+end
+
+Rake::TestTask.new(:test)
+task :test => :compile
+task :default => :compile
+
+c_files = File.readlines('MANIFEST').grep(%r{ext/.*\.[ch]$}).map!(&:chomp!)
+task 'compile:mwrap' => c_files
diff --git a/bin/mwrap b/bin/mwrap
new file mode 100755
index 0000000..17e3570
--- /dev/null
+++ b/bin/mwrap
@@ -0,0 +1,17 @@
+#!/usr/bin/ruby
+# frozen_string_literal: true
+require 'mwrap'
+mwrap_so = $".grep(%r{/mwrap\.so\z})[0] or abort "mwrap.so not loaded"
+cur = ENV['LD_PRELOAD']
+ENV['LD_PRELOAD'] = cur ? "#{mwrap_so}:#{cur}" : mwrap_so
+
+# work around close-on-exec by default behavior in Ruby:
+opts = {}
+if ENV['MWRAP'] =~ /dump_fd:(\d+)/
+  dump_fd = $1.to_i
+  if dump_fd > 2
+    dump_io = IO.new(dump_fd)
+    opts[dump_fd] = dump_io
+  end
+end
+exec *ARGV, opts
diff --git a/ext/mwrap/extconf.rb b/ext/mwrap/extconf.rb
new file mode 100644
index 0000000..dbffd99
--- /dev/null
+++ b/ext/mwrap/extconf.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+# Copyright (C) 2018 mwrap hackers <mwrap-public@80x24.org>
+# License: GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+require 'mkmf'
+
+have_func 'mempcpy'
+if RUBY_PLATFORM =~ /linux/ # should detect glibc
+  if File.read("/proc/#$$/maps") =~ /\blibjemalloc\./
+    $defs << '-DRUBY_USES_JEMALLOC'
+  end
+end
+have_library 'dl'
+create_makefile 'mwrap'
diff --git a/ext/mwrap/mwrap.c b/ext/mwrap/mwrap.c
new file mode 100644
index 0000000..a302d8f
--- /dev/null
+++ b/ext/mwrap/mwrap.c
@@ -0,0 +1,325 @@
+/*
+ * Copyright (C) 2018 mwrap hackers <mwrap-public@80x24.org>
+ * License: GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+ */
+#include <ruby/ruby.h>
+#include <ruby/thread.h>
+#include <ruby/util.h>
+#include <ruby/st.h>
+#include <ruby/io.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <dlfcn.h>
+#include <assert.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+const char *rb_source_location_cstr(int *line); /* requires 2.6.0dev */
+static int *(*has_gvl_p)(void);
+static void *(*real_malloc)(size_t);
+static void *(*real_calloc)(size_t, size_t);
+static void *(*real_realloc)(void *, size_t);
+
+/*
+ * rb_source_location_cstr relies on GET_EC(), and it's possible
+ * to have a native thread but no EC during the early and late
+ * (teardown) phases of the Ruby process
+ */
+static void **ec_loc;
+
+/*
+ * we need to fake an OOM condition while dlsym is running,
+ * as that calls calloc under glibc, but we don't have the
+ * symbol for the jemalloc calloc, yet
+ */
+#  define RETURN_IF_NOT_READY(x) do { \
+        if (!x) { \
+                errno = ENOMEM; \
+                return NULL; \
+        } \
+} while (0)
+
+__attribute__((constructor)) static void resolve_malloc(void)
+{
+        real_calloc = dlsym(RTLD_NEXT, "calloc");
+        real_malloc = dlsym(RTLD_NEXT, "malloc");
+        real_realloc = dlsym(RTLD_NEXT, "realloc");
+        assert(real_calloc && real_malloc && real_realloc);
+
+        has_gvl_p = dlsym(RTLD_DEFAULT, "ruby_thread_has_gvl_p");
+
+        /*
+         * resolve dynamically so it doesn't break when LD_PRELOAD-ed
+         * into non-Ruby binaries
+         */
+        ec_loc = dlsym(RTLD_DEFAULT, "ruby_current_execution_context_ptr");
+}
+
+#ifndef HAVE_MEMPCPY
+#  define mempcpy(dst,src,n) ((char *)memcpy((dst),(src),(n)) + n)
+#endif
+
+/* stolen from glibc: */
+#define RETURN_ADDRESS(nr) \
+  __builtin_extract_return_addr(__builtin_return_address(nr))
+
+static __thread size_t locating;
+static st_table *stats;        /* rb_source_location => size */
+
+/* bytes allocated outside of GVL */
+static size_t unknown_bytes;
+
+#define INT2STR_MAX (sizeof(int) == 4 ? 10 : 19)
+static char *int2str(int num, char *dst, size_t * size)
+{
+        if (num <= 9) {
+                *size -= 1;
+                *dst++ = (char)(num + '0');
+                return dst;
+        } else {
+                char buf[INT2STR_MAX];
+                char *end = buf + sizeof(buf);
+                char *p = end;
+                size_t adj;
+
+                do {
+                        *size -= 1;
+                        *--p = (char)((num % 10) + '0');
+                        num /= 10;
+                } while (num && *size);
+
+                if (!num) {
+                        adj = end - p;
+                        return mempcpy(dst, p, adj);
+                }
+        }
+        return NULL;
+}
+
+static int
+update_stat(st_data_t *k, st_data_t *v, st_data_t arg, int existing)
+{
+        size_t *total = (size_t *) v;
+        size_t size = arg;
+
+        if (existing) {
+                *total += size;
+        } else {
+                char *key = *(char **)k;
+                *k = (st_data_t)ruby_strdup(key);
+                *total = size;
+        }
+        return ST_CONTINUE;
+}
+
+static int has_ec_p(void)
+{
+        return (ec_loc && *ec_loc);
+}
+
+static void update_stats(size_t size, const void *caller)
+{
+        if (locating++) goto out; /* do not recurse into another *alloc */
+
+        if (has_gvl_p && has_gvl_p() && has_ec_p()) {
+                int line;
+                size_t len;
+                char *key, *dst;
+                const char *ptr = rb_source_location_cstr(&line);
+                size_t int_size = INT2STR_MAX;
+
+                if (!stats) stats = st_init_strtable_with_size(16384);
+                if (!ptr) goto unknown;
+
+                /* avoid vsnprintf or anything which could call malloc here: */
+                len = strlen(ptr);
+                key = alloca(len + 1 + int_size + 1);
+                dst = mempcpy(key, ptr, len);
+                *dst++ = ':';
+                dst = int2str(line, dst, &int_size);
+                if (dst) {
+                        *dst = 0;        /* terminate string */
+                        st_update(stats, (st_data_t)key,
+                                   update_stat, (st_data_t)size);
+                } else {
+                        rb_bug("bad math making key from location %s:%d\n",
+                                ptr, line);
+                }
+        } else { /* TODO: do something with caller */
+unknown:
+                __sync_add_and_fetch(&unknown_bytes, size);
+        }
+out:
+        --locating;
+}
+
+/*
+ * Do we care for *memalign? ruby/gc.c uses it in ways this lib
+ * doesn't care about, but maybe some gems use it, too.
+ */
+void *malloc(size_t size)
+{
+        RETURN_IF_NOT_READY(real_malloc);
+        update_stats(size, RETURN_ADDRESS(0));
+        return real_malloc(size);
+}
+
+void *calloc(size_t nmemb, size_t size)
+{
+        RETURN_IF_NOT_READY(real_calloc);
+        /* ruby_xcalloc already does overflow checking */
+        update_stats(nmemb * size, RETURN_ADDRESS(0));
+        return real_calloc(nmemb, size);
+}
+
+void *realloc(void *ptr, size_t size)
+{
+        RETURN_IF_NOT_READY(real_realloc);
+        update_stats(size, RETURN_ADDRESS(0));
+        return real_realloc(ptr, size);
+}
+
+struct dump_arg {
+        FILE *fp;
+        size_t min;
+};
+
+static int dump_i(const char *key, size_t val, struct dump_arg *a)
+{
+        if (val > a->min) {
+                fprintf(a->fp, "%20" PRIuSIZE " %s\n", val, key);
+        }
+
+        return ST_CONTINUE;
+}
+
+static VALUE dump_to_file(VALUE x)
+{
+        struct dump_arg *a = (struct dump_arg *)x;
+
+        if (stats) st_foreach(stats, dump_i, (st_data_t) a);
+        if (unknown_bytes > a->min) {
+                fprintf(a->fp, "%20" PRIuSIZE " (unknown[%d])\n",
+                        unknown_bytes, getpid());
+        }
+
+        return Qnil;
+}
+
+static VALUE dump_ensure(VALUE ignored)
+{
+        --locating;
+        return Qfalse;
+}
+
+static VALUE mwrap_dump(int argc, VALUE * argv, VALUE mod)
+{
+        VALUE io, min;
+        struct dump_arg a;
+        rb_io_t *fptr;
+
+        rb_scan_args(argc, argv, "02", &io, &min);
+
+        if (NIL_P(io))
+                io = *((VALUE *)dlsym(RTLD_DEFAULT, "rb_stderr"));
+
+        a.min = NIL_P(min) ? 0 : NUM2SIZET(min);
+        io = rb_io_get_write_io(io);
+        GetOpenFile(io, fptr);
+        a.fp = rb_io_stdio_file(fptr);
+
+        ++locating;
+        return rb_ensure(dump_to_file, (VALUE) & a, dump_ensure, Qfalse);
+}
+
+static int clear_i(char *key, size_t val, void *ignored)
+{
+        xfree(key);
+        return ST_DELETE;
+}
+
+static VALUE mwrap_clear(VALUE mod)
+{
+        unknown_bytes = 0;
+        st_foreach(stats, clear_i, 0);
+        return Qnil;
+}
+
+void Init_mwrap(void)
+{
+        VALUE mod = rb_define_module("Mwrap");
+
+        if (!stats) stats = st_init_strtable_with_size(16384);
+
+        rb_define_singleton_method(mod, "dump", mwrap_dump, -1);
+        rb_define_singleton_method(mod, "clear", mwrap_clear, 0);
+}
+
+/* rb_cloexec_open isn't usable by non-Ruby processes */
+#ifndef O_CLOEXEC
+#  define O_CLOEXEC 0
+#endif
+
+__attribute__ ((destructor))
+static void mwrap_dump_destructor(void)
+{
+        const char *opt = getenv("MWRAP");
+        const char *modes[] = { "a", "a+", "w", "w+", "r+" };
+        struct dump_arg a;
+        size_t i;
+        int dump_fd;
+        char *dump_path;
+
+        if (!opt)
+                return;
+
+        ++locating;
+        if ((dump_path = strstr(opt, "dump_path:")) &&
+                        (dump_path += sizeof("dump_path")) &&
+                        *dump_path) {
+                char *end = strchr(dump_path, ',');
+                if (end) {
+                        char *tmp = alloca(end - dump_path + 1);
+                        *((char *)mempcpy(tmp, dump_path, end - dump_path)) = 0;
+                        dump_path = tmp;
+                }
+                dump_fd = open(dump_path, O_CLOEXEC|O_WRONLY|O_APPEND|O_CREAT,
+                                0666);
+                if (dump_fd < 0) {
+                        fprintf(stderr, "open %s failed: %s\n", dump_path,
+                                strerror(errno));
+                        goto out;
+                }
+        }
+        else if (!sscanf(opt, "dump_fd:%d", &dump_fd))
+                goto out;
+
+        if (!sscanf(opt, "dump_min:%zu", &a.min))
+                a.min = 0;
+
+        switch (dump_fd) {
+        case 0: goto out;
+        case 1: a.fp = stdout; break;
+        case 2: a.fp = stderr; break;
+        default:
+                if (dump_fd < 0)
+                        goto out;
+                a.fp = 0;
+
+                for (i = 0; !a.fp && i < 5; i++)
+                        a.fp = fdopen(dump_fd, modes[i]);
+
+                if (!a.fp) {
+                        fprintf(stderr, "failed to open fd=%d: %s\n",
+                                dump_fd, strerror(errno));
+                        goto out;
+                }
+                /* we'll leak some memory here, but this is a destructor */
+        }
+        dump_to_file((VALUE)&a);
+out:
+    --locating;
+}
diff --git a/mwrap.gemspec b/mwrap.gemspec
new file mode 100644
index 0000000..7458395
--- /dev/null
+++ b/mwrap.gemspec
@@ -0,0 +1,29 @@
+git_manifest = `git ls-files 2>/dev/null`.split("\n")
+manifest = File.exist?('MANIFEST') ?
+  File.readlines('MANIFEST').map!(&:chomp).delete_if(&:empty?) : git_manifest
+if git_manifest[0] && manifest != git_manifest
+  tmp = "MANIFEST.#$$.tmp"
+  File.open(tmp, 'w') { |fp| fp.puts(git_manifest.join("\n")) }
+  File.rename(tmp, 'MANIFEST')
+  system('git add MANIFEST')
+end
+
+Gem::Specification.new do |s|
+  s.name = 'mwrap'
+  s.version = '0.0.0'
+  s.homepage = 'https://80x24.org/mwrap.git'
+  s.authors = ["Ruby hackers"]
+  s.summary = 'LD_PRELOAD malloc wrapper for Ruby'
+  s.executables = %w(mwrap)
+  s.files = manifest
+  s.description = <<~EOF
+  EOF
+
+  s.email = %q{e@80x24.org}
+  s.test_files = Dir['test/test_*.rb']
+  s.extensions = %w(ext/mwrap/extconf.rb)
+
+  s.add_development_dependency('test-unit', '~> 3.0')
+  s.add_development_dependency('rake-compiler', '~> 1.0')
+  s.licenses = %w(GPL-2.0+)
+end
diff --git a/test/test_mwrap.rb b/test/test_mwrap.rb
new file mode 100644
index 0000000..99073ba
--- /dev/null
+++ b/test/test_mwrap.rb
@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+# Copyright (C) 2018 mwrap hackers <mwrap-public@80x24.org>
+# License: GPL-2.0+ <https://www.gnu.org/licenses/gpl-2.0.txt>
+require 'test/unit'
+require 'mwrap'
+require 'rbconfig'
+require 'tempfile'
+
+class TestMwrap < Test::Unit::TestCase
+  RB = "#{RbConfig::CONFIG['bindir']}/#{RbConfig::CONFIG['RUBY_INSTALL_NAME']}"
+
+  mwrap_so = $".grep(%r{/mwrap\.so\z})[0]
+  env = ENV.to_hash
+  cur = env['LD_PRELOAD']
+  env['LD_PRELOAD'] = cur ? "#{mwrap_so}:#{cur}".freeze : mwrap_so
+  @@env = env.freeze
+  inc = File.dirname(mwrap_so)
+  @@cmd = %W(#{RB} -w --disable=gems -I#{inc} -rmwrap).freeze
+
+  def test_mwrap_preload
+    cmd = @@cmd + %w(
+      -e ("helloworld"*1000).clear
+      -e Mwrap.dump
+    )
+    Tempfile.create('junk') do |tmp|
+      tmp.sync = true
+      res = system(@@env, *cmd, err: tmp)
+      assert res, $?.inspect
+      tmp.rewind
+      lines = tmp.readlines
+      line_1 = lines.grep(/\s-e:1\b/)[0].strip
+      assert_equal '10001', line_1.split(/\s+/)[0]
+    end
+  end
+
+  def test_dump_via_destructor
+    env = @@env.dup
+    env['MWRAP'] = 'dump_fd:5'
+    cmd = @@cmd + %w(-e ("0"*10000).clear)
+    Tempfile.create('junk') do |tmp|
+      tmp.sync = true
+      res = system(env, *cmd, { 5 => tmp })
+      assert res, $?.inspect
+      tmp.rewind
+      assert_match(/\b10001\s+-e:1$/, tmp.read)
+
+      env['MWRAP'] = 'dump_fd:1,dump_min:10000'
+      tmp.rewind
+      tmp.truncate(0)
+      res = system(env, *cmd, { 1 => tmp })
+      assert res, $?.inspect
+      tmp.rewind
+      assert_match(/\b10001\s+-e:1$/, tmp.read)
+
+      tmp.rewind
+      tmp.truncate(0)
+      env['MWRAP'] = "dump_path:#{tmp.path},dump_min:10000"
+      res = system(env, *cmd)
+      assert res, $?.inspect
+      assert_match(/\b10001\s+-e:1$/, tmp.read)
+    end
+  end
+
+  def test_clear
+    cmd = @@cmd + %w(
+      -e ("0"*10000).clear
+      -e Mwrap.clear
+      -e ("0"*20000).clear
+      -e Mwrap.dump($stdout,9999)
+    )
+    Tempfile.create('junk') do |tmp|
+      tmp.sync = true
+      res = system(@@env, *cmd, { 1 => tmp })
+      assert res, $?.inspect
+      tmp.rewind
+      buf = tmp.read
+      assert_not_match(/\s+-e:1$/, buf)
+      assert_match(/\b20001\s+-e:3$/, buf)
+    end
+  end
+
+  # make sure we don't break commands spawned by an mwrap-ed Ruby process:
+  def test_non_ruby_exec
+    IO.pipe do |r, w|
+      th = Thread.new { r.read }
+      Tempfile.create('junk') do |tmp|
+        tmp.sync = true
+        env = @@env.merge('MWRAP' => "dump_path:#{tmp.path}")
+        cmd = %w(perl -e print("HELLO_WORLD"))
+        res = system(env, *cmd, out: w)
+        w.close
+        assert res, $?.inspect
+        assert_match(/unknown/, tmp.read)
+      end
+      assert_equal "HELLO_WORLD", th.value
+    end
+  end
+end