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diff --git a/src/util/win32/w32_leakcheck.h b/src/util/win32/w32_leakcheck.h
new file mode 100644
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+++ b/src/util/win32/w32_leakcheck.h
@@ -0,0 +1,222 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#ifndef INCLUDE_win32_leakcheck_h__
+#define INCLUDE_win32_leakcheck_h__
+
+#include "git2_util.h"
+
+/* Initialize the win32 leak checking system. */
+int git_win32_leakcheck_global_init(void);
+
+#if defined(GIT_WIN32_LEAKCHECK)
+
+#include <stdlib.h>
+#include <crtdbg.h>
+
+#include "git2/errors.h"
+#include "strnlen.h"
+
+bool git_win32_leakcheck_has_leaks(void);
+
+/* Stack frames (for stack tracing, below) */
+
+/**
+ * This type defines a callback to be used to augment a C stacktrace
+ * with "aux" data. This can be used, for example, to allow LibGit2Sharp
+ * (or other interpreted consumer libraries) to give us C# stacktrace
+ * data for the PInvoke.
+ *
+ * This callback will be called during crtdbg-instrumented allocs.
+ *
+ * @param aux_id [out] A returned "aux_id" representing a unique
+ * (de-duped at the C# layer) stacktrace.  "aux_id" 0 is reserved
+ * to mean no aux stacktrace data.
+ */
+typedef void (*git_win32_leakcheck_stack_aux_cb_alloc)(unsigned int *aux_id);
+
+/**
+ * This type defines a callback to be used to augment the output of
+ * a stacktrace.  This will be used to request the C# layer format
+ * the C# stacktrace associated with "aux_id" into the provided
+ * buffer.
+ *
+ * This callback will be called during leak reporting.
+ *
+ * @param aux_id The "aux_id" key associated with a stacktrace.
+ * @param aux_msg A buffer where a formatted message should be written.
+ * @param aux_msg_len The size of the buffer.
+ */
+typedef void (*git_win32_leakcheck_stack_aux_cb_lookup)(unsigned int aux_id, char *aux_msg, size_t aux_msg_len);
+
+/**
+ * Register an "aux" data provider to augment our C stacktrace data.
+ *
+ * This can be used, for example, to allow LibGit2Sharp (or other
+ * interpreted consumer libraries) to give us the C# stacktrace of
+ * the PInvoke.
+ *
+ * If you choose to use this feature, it should be registered during
+ * initialization and not changed for the duration of the process.
+ */
+int git_win32_leakcheck_stack_set_aux_cb(
+	git_win32_leakcheck_stack_aux_cb_alloc cb_alloc,
+	git_win32_leakcheck_stack_aux_cb_lookup cb_lookup);
+
+/**
+ * Maximum number of stackframes to record for a
+ * single stacktrace.
+ */
+#define GIT_WIN32_LEAKCHECK_STACK_MAX_FRAMES 30
+
+/**
+ * Wrapper containing the raw unprocessed stackframe
+ * data for a single stacktrace and any "aux_id".
+ *
+ * I put the aux_id first so leaks will be sorted by it.
+ * So, for example, if a specific callstack in C# leaks
+ * a repo handle, all of the pointers within the associated
+ * repo pointer will be grouped together.
+ */
+typedef struct {
+	unsigned int aux_id;
+	unsigned int nr_frames;
+	void *frames[GIT_WIN32_LEAKCHECK_STACK_MAX_FRAMES];
+} git_win32_leakcheck_stack_raw_data;
+
+/**
+ * Capture raw stack trace data for the current process/thread.
+ *
+ * @param skip Number of initial frames to skip.  Pass 0 to
+ * begin with the caller of this routine. Pass 1 to begin
+ * with its caller.  And so on.
+ */
+int git_win32_leakcheck_stack_capture(git_win32_leakcheck_stack_raw_data *pdata, int skip);
+
+/**
+ * Compare 2 raw stacktraces with the usual -1,0,+1 result.
+ * This includes any "aux_id" values in the comparison, so that
+ * our de-dup is also "aux" context relative.
+ */
+int git_win32_leakcheck_stack_compare(
+	git_win32_leakcheck_stack_raw_data *d1,
+	git_win32_leakcheck_stack_raw_data *d2);
+
+/**
+ * Format raw stacktrace data into buffer WITHOUT using any mallocs.
+ *
+ * @param prefix String written before each frame; defaults to "\t".
+ * @param suffix String written after each frame; defaults to "\n".
+ */
+int git_win32_leakcheck_stack_format(
+	char *pbuf, size_t buf_len,
+	const git_win32_leakcheck_stack_raw_data *pdata,
+	const char *prefix, const char *suffix);
+
+/**
+ * Convenience routine to capture and format stacktrace into
+ * a buffer WITHOUT using any mallocs.  This is primarily a
+ * wrapper for testing.
+ *
+ * @param skip Number of initial frames to skip. Pass 0 to
+ * begin with the caller of this routine.  Pass 1 to begin
+ * with its caller.  And so on.
+ * @param prefix String written before each frame; defaults to "\t".
+ * @param suffix String written after each frame; defaults to "\n".
+ */
+int git_win32_leakcheck_stack(
+	char * pbuf, size_t buf_len,
+	int skip,
+	const char *prefix, const char *suffix);
+
+/* Stack tracing */
+
+/* MSVC CRTDBG memory leak reporting.
+ *
+ * We DO NOT use the "_CRTDBG_MAP_ALLOC" macro described in the MSVC
+ * documentation because all allocs/frees in libgit2 already go through
+ * the "git__" routines defined in this file.  Simply using the normal
+ * reporting mechanism causes all leaks to be attributed to a routine
+ * here in util.h (ie, the actual call to calloc()) rather than the
+ * caller of git__calloc().
+ *
+ * Therefore, we declare a set of "git__crtdbg__" routines to replace
+ * the corresponding "git__" routines and re-define the "git__" symbols
+ * as macros.  This allows us to get and report the file:line info of
+ * the real caller.
+ *
+ * We DO NOT replace the "git__free" routine because it needs to remain
+ * a function pointer because it is used as a function argument when
+ * setting up various structure "destructors".
+ *
+ * We also DO NOT use the "_CRTDBG_MAP_ALLOC" macro because it causes
+ * "free" to be remapped to "_free_dbg" and this causes problems for
+ * structures which define a field named "free".
+ *
+ * Finally, CRTDBG must be explicitly enabled and configured at program
+ * startup.  See tests/main.c for an example.
+ */
+
+/**
+ * Checkpoint options.
+ */
+typedef enum git_win32_leakcheck_stacktrace_options {
+	/**
+	 * Set checkpoint marker.
+	 */
+	GIT_WIN32_LEAKCHECK_STACKTRACE_SET_MARK         = (1 << 0),
+
+	/**
+	 * Dump leaks since last checkpoint marker.
+	 * May not be combined with _LEAKS_TOTAL.
+	 *
+	 * Note that this may generate false positives for global TLS
+	 * error state and other global caches that aren't cleaned up
+	 * until the thread/process terminates.  So when using this
+	 * around a region of interest, also check the final (at exit)
+	 * dump before digging into leaks reported here.
+	 */
+	GIT_WIN32_LEAKCHECK_STACKTRACE_LEAKS_SINCE_MARK = (1 << 1),
+
+	/**
+	 * Dump leaks since init.  May not be combined
+	 * with _LEAKS_SINCE_MARK.
+	 */
+	GIT_WIN32_LEAKCHECK_STACKTRACE_LEAKS_TOTAL      = (1 << 2),
+
+	/**
+	 * Suppress printing during dumps.
+	 * Just return leak count.
+	 */
+	GIT_WIN32_LEAKCHECK_STACKTRACE_QUIET            = (1 << 3),
+
+} git_win32_leakcheck_stacktrace_options;
+
+/**
+ * Checkpoint memory state and/or dump unique stack traces of
+ * current memory leaks.
+ *
+ * @return number of unique leaks (relative to requested starting
+ * point) or error.
+ */
+int git_win32_leakcheck_stacktrace_dump(
+	git_win32_leakcheck_stacktrace_options opt,
+	const char *label);
+
+/**
+ * Construct stacktrace and append it to the global buffer.
+ * Return pointer to start of this string.  On any error or
+ * lack of buffer space, just return the given file buffer
+ * so it will behave as usual.
+ *
+ * This should ONLY be called by our internal memory allocations
+ * routines.
+ */
+const char *git_win32_leakcheck_stacktrace(int skip, const char *file);
+
+#endif
+#endif