thodg/libgit2

diff --git a/CMakeLists.txt b/CMakeLists.txt
index eff2500..bc3f07c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -74,14 +74,6 @@ IF (APPLE)
 ENDIF()
 
 IF(MSVC)
-	# This option is only available when building with MSVC. By default, libgit2
-	# is build using the cdecl calling convention, which is useful if you're
-	# writing C. However, the CLR and Win32 API both expect stdcall.
-	#
-	# If you are writing a CLR program and want to link to libgit2, you'll want
-	# to turn this on by invoking CMake with the "-DSTDCALL=ON" argument.
-	OPTION(STDCALL			"Build libgit2 with the __stdcall convention"		OFF)
-
 	# This option must match the settings used in your program, in particular if you
 	# are linking statically
 	OPTION(STATIC_CRT		"Link the static CRT libraries"		 		 ON)
@@ -115,6 +107,10 @@ STRING(REGEX REPLACE "^.*LIBGIT2_SOVERSION ([0-9]+)$" "\\1" LIBGIT2_SOVERSION "$
 
 # Platform specific compilation flags
 IF (MSVC)
+	IF (STDCALL)
+		MESSAGE(FATAL_ERROR "The STDCALL option is no longer supported; libgit2 is now always built as a cdecl library.  If you're using PInvoke, please add the CallingConventions.Cdecl attribute for support.")
+	ENDIF()
+
 	ADD_DEFINITIONS(-D_SCL_SECURE_NO_WARNINGS)
 	ADD_DEFINITIONS(-D_CRT_SECURE_NO_DEPRECATE)
 	ADD_DEFINITIONS(-D_CRT_NONSTDC_NO_DEPRECATE)
@@ -125,10 +121,8 @@ IF (MSVC)
 	# /MP - Parallel build
 	SET(CMAKE_C_FLAGS "/GF /MP /nologo ${CMAKE_C_FLAGS}")
 
-	IF (STDCALL)
-		# /Gz - stdcall calling convention
-		SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Gz")
-	ENDIF ()
+	# /Gd - explicitly set cdecl calling convention
+	SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /Gd")
 
 	IF (STATIC_CRT)
 		SET(CRT_FLAG_DEBUG "/MTd")
diff --git a/README.md b/README.md
index 69ddfd6..8569df0 100644
--- a/README.md
+++ b/README.md
@@ -255,7 +255,6 @@ The following CMake variables are declared:
 - `BUILD_SHARED_LIBS`: Build libgit2 as a Shared Library (defaults to ON)
 - `BUILD_CLAR`: Build [Clar](https://github.com/vmg/clar)-based test suite (defaults to ON)
 - `THREADSAFE`: Build libgit2 with threading support (defaults to ON)
-- `STDCALL`: Build libgit2 as `stdcall`. Turn off for `cdecl` (Windows; defaults to ON)
 
 To list all build options and their current value, you can do the
 following:
diff --git a/docs/changelog.md b/docs/changelog.md
index d4fc413..26899a5 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -3,6 +3,9 @@ v0.27 + 1
 
 ### Changes or improvements
 
+* The library is now always built with cdecl calling conventions on
+  Windows; the ability to build a stdcall library has been removed.
+
 * Reference log creation now honors `core.logallrefupdates=always`.
 
 * Fix some issues with the error-reporting in the OpenSSL backend.
diff --git a/include/git2/apply.h b/include/git2/apply.h
index 7cc1c22..91f93d7 100644
--- a/include/git2/apply.h
+++ b/include/git2/apply.h
@@ -33,7 +33,7 @@ GIT_BEGIN_DECL
  * @param delta The delta to be applied
  * @param payload User-specified payload
  */
-typedef int (*git_apply_delta_cb)(
+typedef int GIT_CALLBACK(git_apply_delta_cb)(
 	const git_diff_delta *delta,
 	void *payload);
 
@@ -49,7 +49,7 @@ typedef int (*git_apply_delta_cb)(
  * @param hunk The hunk to be applied
  * @param payload User-specified payload
  */
-typedef int (*git_apply_hunk_cb)(
+typedef int GIT_CALLBACK(git_apply_hunk_cb)(
 	const git_diff_hunk *hunk,
 	void *payload);
 
diff --git a/include/git2/attr.h b/include/git2/attr.h
index 651454a..3752b99 100644
--- a/include/git2/attr.h
+++ b/include/git2/attr.h
@@ -202,7 +202,7 @@ GIT_EXTERN(int) git_attr_get_many(
  * @return 0 to continue looping, non-zero to stop. This value will be returned
  *         from git_attr_foreach.
  */
-typedef int (*git_attr_foreach_cb)(const char *name, const char *value, void *payload);
+typedef int GIT_CALLBACK(git_attr_foreach_cb)(const char *name, const char *value, void *payload);
 
 /**
  * Loop over all the git attributes for a path.
diff --git a/include/git2/buffer.h b/include/git2/buffer.h
index c06e2b2..050afb9 100644
--- a/include/git2/buffer.h
+++ b/include/git2/buffer.h
@@ -81,7 +81,7 @@ GIT_EXTERN(void) git_buf_dispose(git_buf *buffer);
  *
  * This function is going to be removed in v0.30.0.
  */
-GIT_EXTERN(void) GIT_DEPRECATED(git_buf_free)(git_buf *buffer);
+GIT_DEPRECATED(GIT_EXTERN(void)) git_buf_free(git_buf *buffer);
 
 /**
  * Resize the buffer allocation to make more space.
diff --git a/include/git2/checkout.h b/include/git2/checkout.h
index 485bae6..2953637 100644
--- a/include/git2/checkout.h
+++ b/include/git2/checkout.h
@@ -220,7 +220,7 @@ typedef struct {
 } git_checkout_perfdata;
 
 /** Checkout notification callback function */
-typedef int (*git_checkout_notify_cb)(
+typedef int GIT_CALLBACK(git_checkout_notify_cb)(
 	git_checkout_notify_t why,
 	const char *path,
 	const git_diff_file *baseline,
@@ -229,14 +229,14 @@ typedef int (*git_checkout_notify_cb)(
 	void *payload);
 
 /** Checkout progress notification function */
-typedef void (*git_checkout_progress_cb)(
+typedef void GIT_CALLBACK(git_checkout_progress_cb)(
 	const char *path,
 	size_t completed_steps,
 	size_t total_steps,
 	void *payload);
 
 /** Checkout perfdata notification function */
-typedef void (*git_checkout_perfdata_cb)(
+typedef void GIT_CALLBACK(git_checkout_perfdata_cb)(
 	const git_checkout_perfdata *perfdata,
 	void *payload);
 
diff --git a/include/git2/clone.h b/include/git2/clone.h
index 4690317..4a64aac 100644
--- a/include/git2/clone.h
+++ b/include/git2/clone.h
@@ -66,7 +66,7 @@ typedef enum {
  * @param payload an opaque payload
  * @return 0, GIT_EINVALIDSPEC, GIT_EEXISTS or an error code
  */
-typedef int (*git_remote_create_cb)(
+typedef int GIT_CALLBACK(git_remote_create_cb)(
 	git_remote **out,
 	git_repository *repo,
 	const char *name,
@@ -87,7 +87,7 @@ typedef int (*git_remote_create_cb)(
  * @param payload payload specified by the options
  * @return 0, or a negative value to indicate error
  */
-typedef int (*git_repository_create_cb)(
+typedef int GIT_CALLBACK(git_repository_create_cb)(
 	git_repository **out,
 	const char *path,
 	int bare,
diff --git a/include/git2/common.h b/include/git2/common.h
index 82f6ba4..8d3d3c1 100644
--- a/include/git2/common.h
+++ b/include/git2/common.h
@@ -43,11 +43,18 @@ typedef size_t size_t;
 			 __attribute__((visibility("default"))) \
 			 type
 #elif defined(_MSC_VER)
-# define GIT_EXTERN(type) __declspec(dllexport) type
+# define GIT_EXTERN(type) __declspec(dllexport) type __cdecl
 #else
 # define GIT_EXTERN(type) extern type
 #endif
 
+/** Declare a callback function for application use. */
+#if defined(_MSC_VER)
+# define GIT_CALLBACK(name) (__cdecl *name)
+#else
+# define GIT_CALLBACK(name) (*name)
+#endif
+
 /** Declare a function as deprecated. */
 #if defined(__GNUC__)
 # define GIT_DEPRECATED(func) \
diff --git a/include/git2/config.h b/include/git2/config.h
index f32f7af..0bea323 100644
--- a/include/git2/config.h
+++ b/include/git2/config.h
@@ -66,7 +66,7 @@ typedef struct git_config_entry {
 	const char *value; /**< String value of the entry */
 	unsigned int include_depth; /**< Depth of includes where this variable was found */
 	git_config_level_t level; /**< Which config file this was found in */
-	void (*free)(struct git_config_entry *entry); /**< Free function for this entry */
+	void GIT_CALLBACK(free)(struct git_config_entry *entry); /**< Free function for this entry */
 	void *payload; /**< Opaque value for the free function. Do not read or write */
 } git_config_entry;
 
@@ -81,7 +81,7 @@ GIT_EXTERN(void) git_config_entry_free(git_config_entry *);
  * @param entry the entry currently being enumerated
  * @param payload a user-specified pointer
  */
-typedef int  (*git_config_foreach_cb)(const git_config_entry *entry, void *payload);
+typedef int GIT_CALLBACK(git_config_foreach_cb)(const git_config_entry *entry, void *payload);
 
 /**
  * An opaque structure for a configuration iterator
diff --git a/include/git2/diff.h b/include/git2/diff.h
index b64bf20..b920385 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -328,7 +328,7 @@ typedef struct {
  * - returns 0, the delta is inserted into the diff, and the diff process
  *		continues.
  */
-typedef int (*git_diff_notify_cb)(
+typedef int GIT_CALLBACK(git_diff_notify_cb)(
 	const git_diff *diff_so_far,
 	const git_diff_delta *delta_to_add,
 	const char *matched_pathspec,
@@ -344,7 +344,7 @@ typedef int (*git_diff_notify_cb)(
  * @param new_path The path to the new file or NULL.
  * @return Non-zero to abort the diff.
  */
-typedef int (*git_diff_progress_cb)(
+typedef int GIT_CALLBACK(git_diff_progress_cb)(
 	const git_diff *diff_so_far,
 	const char *old_path,
 	const char *new_path,
@@ -462,7 +462,7 @@ GIT_EXTERN(int) git_diff_init_options(
  * @param progress Goes from 0 to 1 over the diff
  * @param payload User-specified pointer from foreach function
  */
-typedef int (*git_diff_file_cb)(
+typedef int GIT_CALLBACK(git_diff_file_cb)(
 	const git_diff_delta *delta,
 	float progress,
 	void *payload);
@@ -528,7 +528,7 @@ typedef struct {
  * When iterating over a diff, callback that will be made for
  * binary content within the diff.
  */
-typedef int(*git_diff_binary_cb)(
+typedef int GIT_CALLBACK(git_diff_binary_cb)(
 	const git_diff_delta *delta,
 	const git_diff_binary *binary,
 	void *payload);
@@ -554,7 +554,7 @@ typedef struct {
 /**
  * When iterating over a diff, callback that will be made per hunk.
  */
-typedef int (*git_diff_hunk_cb)(
+typedef int GIT_CALLBACK(git_diff_hunk_cb)(
 	const git_diff_delta *delta,
 	const git_diff_hunk *hunk,
 	void *payload);
@@ -615,7 +615,7 @@ typedef struct {
  * of text.  This uses some extra GIT_DIFF_LINE_... constants for output
  * of lines of file and hunk headers.
  */
-typedef int (*git_diff_line_cb)(
+typedef int GIT_CALLBACK(git_diff_line_cb)(
 	const git_diff_delta *delta, /**< delta that contains this data */
 	const git_diff_hunk *hunk,   /**< hunk containing this data */
 	const git_diff_line *line,   /**< line data */
@@ -699,14 +699,14 @@ typedef enum {
  * Pluggable similarity metric
  */
 typedef struct {
-	int (*file_signature)(
+	int GIT_CALLBACK(file_signature)(
 		void **out, const git_diff_file *file,
 		const char *fullpath, void *payload);
-	int (*buffer_signature)(
+	int GIT_CALLBACK(buffer_signature)(
 		void **out, const git_diff_file *file,
 		const char *buf, size_t buflen, void *payload);
-	void (*free_signature)(void *sig, void *payload);
-	int (*similarity)(int *score, void *siga, void *sigb, void *payload);
+	void GIT_CALLBACK(free_signature)(void *sig, void *payload);
+	int GIT_CALLBACK(similarity)(int *score, void *siga, void *sigb, void *payload);
 	void *payload;
 } git_diff_similarity_metric;
 
diff --git a/include/git2/index.h b/include/git2/index.h
index 9d73ce2..80e15c6 100644
--- a/include/git2/index.h
+++ b/include/git2/index.h
@@ -132,7 +132,7 @@ typedef enum {
 
 
 /** Callback for APIs that add/remove/update files matching pathspec */
-typedef int (*git_index_matched_path_cb)(
+typedef int GIT_CALLBACK(git_index_matched_path_cb)(
 	const char *path, const char *matched_pathspec, void *payload);
 
 /** Flags for APIs that add files matching pathspec */
diff --git a/include/git2/net.h b/include/git2/net.h
index 04dff34..391cdee 100644
--- a/include/git2/net.h
+++ b/include/git2/net.h
@@ -52,7 +52,7 @@ struct git_remote_head {
 /**
  * Callback for listing the remote heads
  */
-typedef int (*git_headlist_cb)(git_remote_head *rhead, void *payload);
+typedef int GIT_CALLBACK(git_headlist_cb)(git_remote_head *rhead, void *payload);
 
 /** @} */
 GIT_END_DECL
diff --git a/include/git2/notes.h b/include/git2/notes.h
index 853e5de..c36149e 100644
--- a/include/git2/notes.h
+++ b/include/git2/notes.h
@@ -26,7 +26,7 @@ GIT_BEGIN_DECL
  * - annotated_object_id: Oid of the git object being annotated
  * - payload: Payload data passed to `git_note_foreach`
  */
-typedef int (*git_note_foreach_cb)(
+typedef int GIT_CALLBACK(git_note_foreach_cb)(
 	const git_oid *blob_id, const git_oid *annotated_object_id, void *payload);
 
 /**
diff --git a/include/git2/odb.h b/include/git2/odb.h
index b752b90..0008eee 100644
--- a/include/git2/odb.h
+++ b/include/git2/odb.h
@@ -24,7 +24,7 @@ GIT_BEGIN_DECL
 /**
  * Function type for callbacks from git_odb_foreach.
  */
-typedef int (*git_odb_foreach_cb)(const git_oid *id, void *payload);
+typedef int GIT_CALLBACK(git_odb_foreach_cb)(const git_oid *id, void *payload);
 
 /**
  * Create a new object database with no backends.
diff --git a/include/git2/odb_backend.h b/include/git2/odb_backend.h
index 9199538..614d0d4 100644
--- a/include/git2/odb_backend.h
+++ b/include/git2/odb_backend.h
@@ -92,12 +92,12 @@ struct git_odb_stream {
 	/**
 	 * Write at most `len` bytes into `buffer` and advance the stream.
 	 */
-	int (*read)(git_odb_stream *stream, char *buffer, size_t len);
+	int GIT_CALLBACK(read)(git_odb_stream *stream, char *buffer, size_t len);
 
 	/**
 	 * Write `len` bytes from `buffer` into the stream.
 	 */
-	int (*write)(git_odb_stream *stream, const char *buffer, size_t len);
+	int GIT_CALLBACK(write)(git_odb_stream *stream, const char *buffer, size_t len);
 
 	/**
 	 * Store the contents of the stream as an object with the id
@@ -109,7 +109,7 @@ struct git_odb_stream {
 	 * - the final number of received bytes differs from the size declared
 	 *   with `git_odb_open_wstream()`
 	 */
-	int (*finalize_write)(git_odb_stream *stream, const git_oid *oid);
+	int GIT_CALLBACK(finalize_write)(git_odb_stream *stream, const git_oid *oid);
 
 	/**
 	 * Free the stream's memory.
@@ -117,16 +117,16 @@ struct git_odb_stream {
 	 * This method might be called without a call to `finalize_write` if
 	 * an error occurs or if the object is already present in the ODB.
 	 */
-	void (*free)(git_odb_stream *stream);
+	void GIT_CALLBACK(free)(git_odb_stream *stream);
 };
 
 /** A stream to write a pack file to the ODB */
 struct git_odb_writepack {
 	git_odb_backend *backend;
 
-	int (*append)(git_odb_writepack *writepack, const void *data, size_t size, git_transfer_progress *stats);
-	int (*commit)(git_odb_writepack *writepack, git_transfer_progress *stats);
-	void (*free)(git_odb_writepack *writepack);
+	int GIT_CALLBACK(append)(git_odb_writepack *writepack, const void *data, size_t size, git_transfer_progress *stats);
+	int GIT_CALLBACK(commit)(git_odb_writepack *writepack, git_transfer_progress *stats);
+	void GIT_CALLBACK(free)(git_odb_writepack *writepack);
 };
 
 GIT_END_DECL
diff --git a/include/git2/pack.h b/include/git2/pack.h
index 2dfd825..beb9f4b 100644
--- a/include/git2/pack.h
+++ b/include/git2/pack.h
@@ -178,7 +178,7 @@ GIT_EXTERN(int) git_packbuilder_write(
 */
 GIT_EXTERN(const git_oid *) git_packbuilder_hash(git_packbuilder *pb);
 
-typedef int (*git_packbuilder_foreach_cb)(void *buf, size_t size, void *payload);
+typedef int GIT_CALLBACK(git_packbuilder_foreach_cb)(void *buf, size_t size, void *payload);
 
 /**
  * Create the new pack and pass each object to the callback
@@ -207,7 +207,7 @@ GIT_EXTERN(size_t) git_packbuilder_object_count(git_packbuilder *pb);
 GIT_EXTERN(size_t) git_packbuilder_written(git_packbuilder *pb);
 
 /** Packbuilder progress notification function */
-typedef int (*git_packbuilder_progress)(
+typedef int GIT_CALLBACK(git_packbuilder_progress)(
 	int stage,
 	uint32_t current,
 	uint32_t total,
diff --git a/include/git2/refs.h b/include/git2/refs.h
index 5504c30..909edea 100644
--- a/include/git2/refs.h
+++ b/include/git2/refs.h
@@ -422,8 +422,8 @@ GIT_EXTERN(int) git_reference_remove(git_repository *repo, const char *name);
  */
 GIT_EXTERN(int) git_reference_list(git_strarray *array, git_repository *repo);
 
-typedef int (*git_reference_foreach_cb)(git_reference *reference, void *payload);
-typedef int (*git_reference_foreach_name_cb)(const char *name, void *payload);
+typedef int GIT_CALLBACK(git_reference_foreach_cb)(git_reference *reference, void *payload);
+typedef int GIT_CALLBACK(git_reference_foreach_name_cb)(const char *name, void *payload);
 
 /**
  * Perform a callback on each reference in the repository.
diff --git a/include/git2/remote.h b/include/git2/remote.h
index 3e8292f..0b6e92a 100644
--- a/include/git2/remote.h
+++ b/include/git2/remote.h
@@ -422,7 +422,7 @@ typedef enum git_remote_completion_type {
 } git_remote_completion_type;
 
 /** Push network progress notification function */
-typedef int (*git_push_transfer_progress)(
+typedef int GIT_CALLBACK(git_push_transfer_progress)(
 	unsigned int current,
 	unsigned int total,
 	size_t bytes,
@@ -457,7 +457,7 @@ typedef struct {
  * @param len number of elements in `updates`
  * @param payload Payload provided by the caller
  */
-typedef int (*git_push_negotiation)(const git_push_update **updates, size_t len, void *payload);
+typedef int GIT_CALLBACK(git_push_negotiation)(const git_push_update **updates, size_t len, void *payload);
 
 /**
  * Callback used to inform of the update status from the remote.
@@ -471,7 +471,7 @@ typedef int (*git_push_negotiation)(const git_push_update **updates, size_t len,
  * @param data data provided by the caller
  * @return 0 on success, otherwise an error
  */
-typedef int (*git_push_update_reference_cb)(const char *refname, const char *status, void *data);
+typedef int GIT_CALLBACK(git_push_update_reference_cb)(const char *refname, const char *status, void *data);
 
 /**
  * The callback settings structure
@@ -492,7 +492,7 @@ struct git_remote_callbacks {
 	 * Completion is called when different parts of the download
 	 * process are done (currently unused).
 	 */
-	int (*completion)(git_remote_completion_type type, void *data);
+	int GIT_CALLBACK(completion)(git_remote_completion_type type, void *data);
 
 	/**
 	 * This will be called if the remote host requires
@@ -522,7 +522,7 @@ struct git_remote_callbacks {
 	 * Each time a reference is updated locally, this function
 	 * will be called with information about it.
 	 */
-	int (*update_tips)(const char *refname, const git_oid *a, const git_oid *b, void *data);
+	int GIT_CALLBACK(update_tips)(const char *refname, const git_oid *a, const git_oid *b, void *data);
 
 	/**
 	 * Function to call with progress information during pack
diff --git a/include/git2/repository.h b/include/git2/repository.h
index 344c203..0386916 100644
--- a/include/git2/repository.h
+++ b/include/git2/repository.h
@@ -627,7 +627,7 @@ GIT_EXTERN(int) git_repository_message_remove(git_repository *repo);
  */
 GIT_EXTERN(int) git_repository_state_cleanup(git_repository *repo);
 
-typedef int (*git_repository_fetchhead_foreach_cb)(const char *ref_name,
+typedef int GIT_CALLBACK(git_repository_fetchhead_foreach_cb)(const char *ref_name,
 	const char *remote_url,
 	const git_oid *oid,
 	unsigned int is_merge,
@@ -649,7 +649,7 @@ GIT_EXTERN(int) git_repository_fetchhead_foreach(
 	git_repository_fetchhead_foreach_cb callback,
 	void *payload);
 
-typedef int (*git_repository_mergehead_foreach_cb)(const git_oid *oid,
+typedef int GIT_CALLBACK(git_repository_mergehead_foreach_cb)(const git_oid *oid,
 	void *payload);
 
 /**
diff --git a/include/git2/revwalk.h b/include/git2/revwalk.h
index 901570e..9cb0d0a 100644
--- a/include/git2/revwalk.h
+++ b/include/git2/revwalk.h
@@ -274,7 +274,7 @@ GIT_EXTERN(git_repository *) git_revwalk_repository(git_revwalk *walk);
  * @param commit_id oid of Commit
  * @param payload User-specified pointer to data to be passed as data payload
  */
-typedef int(*git_revwalk_hide_cb)(
+typedef int GIT_CALLBACK(git_revwalk_hide_cb)(
 	const git_oid *commit_id,
 	void *payload);
 
diff --git a/include/git2/stash.h b/include/git2/stash.h
index 1fdbeb6..c4dcf68 100644
--- a/include/git2/stash.h
+++ b/include/git2/stash.h
@@ -112,7 +112,7 @@ typedef enum {
  * Return 0 to continue processing, or a negative value to
  * abort the stash application.
  */
-typedef int (*git_stash_apply_progress_cb)(
+typedef int GIT_CALLBACK(git_stash_apply_progress_cb)(
 	git_stash_apply_progress_t progress,
 	void *payload);
 
@@ -198,7 +198,7 @@ GIT_EXTERN(int) git_stash_apply(
  * @param payload Extra parameter to callback function.
  * @return 0 to continue iterating or non-zero to stop.
  */
-typedef int (*git_stash_cb)(
+typedef int GIT_CALLBACK(git_stash_cb)(
 	size_t index,
 	const char* message,
 	const git_oid *stash_id,
diff --git a/include/git2/status.h b/include/git2/status.h
index bba0d05..06229ed 100644
--- a/include/git2/status.h
+++ b/include/git2/status.h
@@ -60,7 +60,7 @@ typedef enum {
  *
  * `payload` is the value you passed to the foreach function as payload.
  */
-typedef int (*git_status_cb)(
+typedef int GIT_CALLBACK(git_status_cb)(
 	const char *path, unsigned int status_flags, void *payload);
 
 /**
diff --git a/include/git2/submodule.h b/include/git2/submodule.h
index c5cf006..ac6344e 100644
--- a/include/git2/submodule.h
+++ b/include/git2/submodule.h
@@ -115,7 +115,7 @@ typedef enum {
  * @param payload value you passed to the foreach function as payload
  * @return 0 on success or error code
  */
-typedef int (*git_submodule_cb)(
+typedef int GIT_CALLBACK(git_submodule_cb)(
 	git_submodule *sm, const char *name, void *payload);
 
 /**
diff --git a/include/git2/sys/alloc.h b/include/git2/sys/alloc.h
index 4bc5323..642740d 100644
--- a/include/git2/sys/alloc.h
+++ b/include/git2/sys/alloc.h
@@ -22,54 +22,54 @@ GIT_BEGIN_DECL
  */
 typedef struct {
 	/* Allocate `n` bytes of memory */
-	void *(*gmalloc)(size_t n, const char *file, int line);
+	void * GIT_CALLBACK(gmalloc)(size_t n, const char *file, int line);
 
 	/*
 	 * Allocate memory for an array of `nelem` elements, where each element
 	 * has a size of `elsize`. Returned memory shall be initialized to
 	 * all-zeroes
 	 */
-	void *(*gcalloc)(size_t nelem, size_t elsize, const char *file, int line);
+	void * GIT_CALLBACK(gcalloc)(size_t nelem, size_t elsize, const char *file, int line);
 
 	/* Allocate memory for the string `str` and duplicate its contents. */
-	char *(*gstrdup)(const char *str, const char *file, int line);
+	char * GIT_CALLBACK(gstrdup)(const char *str, const char *file, int line);
 
 	/*
 	 * Equivalent to the `gstrdup` function, but only duplicating at most
 	 * `n + 1` bytes
 	 */
-	char *(*gstrndup)(const char *str, size_t n, const char *file, int line);
+	char * GIT_CALLBACK(gstrndup)(const char *str, size_t n, const char *file, int line);
 
 	/*
 	 * Equivalent to `gstrndup`, but will always duplicate exactly `n` bytes
 	 * of `str`. Thus, out of bounds reads at `str` may happen.
 	 */
-	char *(*gsubstrdup)(const char *str, size_t n, const char *file, int line);
+	char * GIT_CALLBACK(gsubstrdup)(const char *str, size_t n, const char *file, int line);
 
 	/*
 	 * This function shall deallocate the old object `ptr` and return a
 	 * pointer to a new object that has the size specified by `size`. In
 	 * case `ptr` is `NULL`, a new array shall be allocated.
 	 */
-	void *(*grealloc)(void *ptr, size_t size, const char *file, int line);
+	void * GIT_CALLBACK(grealloc)(void *ptr, size_t size, const char *file, int line);
 
 	/*
 	 * This function shall be equivalent to `grealloc`, but allocating
 	 * `neleme * elsize` bytes.
 	 */
-	void *(*greallocarray)(void *ptr, size_t nelem, size_t elsize, const char *file, int line);
+	void * GIT_CALLBACK(greallocarray)(void *ptr, size_t nelem, size_t elsize, const char *file, int line);
 
 	/*
 	 * This function shall allocate a new array of `nelem` elements, where
 	 * each element has a size of `elsize` bytes.
 	 */
-	void *(*gmallocarray)(size_t nelem, size_t elsize, const char *file, int line);
+	void * GIT_CALLBACK(gmallocarray)(size_t nelem, size_t elsize, const char *file, int line);
 
 	/*
 	 * This function shall free the memory pointed to by `ptr`. In case
 	 * `ptr` is `NULL`, this shall be a no-op.
 	 */
-	void (*gfree)(void *ptr);
+	void GIT_CALLBACK(gfree)(void *ptr);
 } git_allocator;
 
 /**
diff --git a/include/git2/sys/commit.h b/include/git2/sys/commit.h
index 627d3ae..ba67106 100644
--- a/include/git2/sys/commit.h
+++ b/include/git2/sys/commit.h
@@ -50,7 +50,7 @@ GIT_EXTERN(int) git_commit_create_from_ids(
  * along with the user supplied payload.  This should return a git_oid of
  * the next parent or NULL if all parents have been provided.
  */
-typedef const git_oid *(*git_commit_parent_callback)(size_t idx, void *payload);
+typedef const git_oid * GIT_CALLBACK(git_commit_parent_callback)(size_t idx, void *payload);
 
 /**
  * Create a new commit in the repository with an callback to supply parents.
diff --git a/include/git2/sys/config.h b/include/git2/sys/config.h
index ed20322..0a9005e 100644
--- a/include/git2/sys/config.h
+++ b/include/git2/sys/config.h
@@ -39,12 +39,12 @@ struct git_config_iterator {
 	 * Return the current entry and advance the iterator. The
 	 * memory belongs to the library.
 	 */
-	int (*next)(git_config_entry **entry, git_config_iterator *iter);
+	int GIT_CALLBACK(next)(git_config_entry **entry, git_config_iterator *iter);
 
 	/**
 	 * Free the iterator
 	 */
-	void (*free)(git_config_iterator *iter);
+	void GIT_CALLBACK(free)(git_config_iterator *iter);
 };
 
 /**
@@ -58,15 +58,15 @@ struct git_config_backend {
 	struct git_config *cfg;
 
 	/* Open means open the file/database and parse if necessary */
-	int (*open)(struct git_config_backend *, git_config_level_t level, const git_repository *repo);
-	int (*get)(struct git_config_backend *, const char *key, git_config_entry **entry);
-	int (*set)(struct git_config_backend *, const char *key, const char *value);
-	int (*set_multivar)(git_config_backend *cfg, const char *name, const char *regexp, const char *value);
-	int (*del)(struct git_config_backend *, const char *key);
-	int (*del_multivar)(struct git_config_backend *, const char *key, const char *regexp);
-	int (*iterator)(git_config_iterator **, struct git_config_backend *);
+	int GIT_CALLBACK(open)(struct git_config_backend *, git_config_level_t level, const git_repository *repo);
+	int GIT_CALLBACK(get)(struct git_config_backend *, const char *key, git_config_entry **entry);
+	int GIT_CALLBACK(set)(struct git_config_backend *, const char *key, const char *value);
+	int GIT_CALLBACK(set_multivar)(git_config_backend *cfg, const char *name, const char *regexp, const char *value);
+	int GIT_CALLBACK(del)(struct git_config_backend *, const char *key);
+	int GIT_CALLBACK(del_multivar)(struct git_config_backend *, const char *key, const char *regexp);
+	int GIT_CALLBACK(iterator)(git_config_iterator **, struct git_config_backend *);
 	/** Produce a read-only version of this backend */
-	int (*snapshot)(struct git_config_backend **, struct git_config_backend *);
+	int GIT_CALLBACK(snapshot)(struct git_config_backend **, struct git_config_backend *);
 	/**
 	 * Lock this backend.
 	 *
@@ -74,14 +74,14 @@ struct git_config_backend {
 	 * backend. Any updates must not be visible to any other
 	 * readers.
 	 */
-	int (*lock)(struct git_config_backend *);
+	int GIT_CALLBACK(lock)(struct git_config_backend *);
 	/**
 	 * Unlock the data store backing this backend. If success is
 	 * true, the changes should be committed, otherwise rolled
 	 * back.
 	 */
-	int (*unlock)(struct git_config_backend *, int success);
-	void (*free)(struct git_config_backend *);
+	int GIT_CALLBACK(unlock)(struct git_config_backend *, int success);
+	void GIT_CALLBACK(free)(struct git_config_backend *);
 };
 #define GIT_CONFIG_BACKEND_VERSION 1
 #define GIT_CONFIG_BACKEND_INIT {GIT_CONFIG_BACKEND_VERSION}
diff --git a/include/git2/sys/filter.h b/include/git2/sys/filter.h
index 6d575d4..e43fde5 100644
--- a/include/git2/sys/filter.h
+++ b/include/git2/sys/filter.h
@@ -138,7 +138,7 @@ GIT_EXTERN(uint32_t) git_filter_source_flags(const git_filter_source *src);
  * initialization operations (in case libgit2 is being used in a way that
  * doesn't need the filter).
  */
-typedef int (*git_filter_init_fn)(git_filter *self);
+typedef int GIT_CALLBACK(git_filter_init_fn)(git_filter *self);
 
 /**
  * Shutdown callback on filter
@@ -150,7 +150,7 @@ typedef int (*git_filter_init_fn)(git_filter *self);
  *
  * Typically this function will free the `git_filter` object itself.
  */
-typedef void (*git_filter_shutdown_fn)(git_filter *self);
+typedef void GIT_CALLBACK(git_filter_shutdown_fn)(git_filter *self);
 
 /**
  * Callback to decide if a given source needs this filter
@@ -172,7 +172,7 @@ typedef void (*git_filter_shutdown_fn)(git_filter *self);
  * callback can use it.  If a filter allocates and assigns a value to the
  * `payload`, it will need a `cleanup` callback to free the payload.
  */
-typedef int (*git_filter_check_fn)(
+typedef int GIT_CALLBACK(git_filter_check_fn)(
 	git_filter  *self,
 	void       **payload, /* points to NULL ptr on entry, may be set */
 	const git_filter_source *src,
@@ -190,14 +190,14 @@ typedef int (*git_filter_check_fn)(
  * The `payload` value will refer to any payload that was set by the
  * `check` callback.  It may be read from or written to as needed.
  */
-typedef int (*git_filter_apply_fn)(
+typedef int GIT_CALLBACK(git_filter_apply_fn)(
 	git_filter    *self,
 	void         **payload, /* may be read and/or set */
 	git_buf       *to,
 	const git_buf *from,
 	const git_filter_source *src);
 
-typedef int (*git_filter_stream_fn)(
+typedef int GIT_CALLBACK(git_filter_stream_fn)(
 	git_writestream **out,
 	git_filter *self,
 	void **payload,
@@ -212,7 +212,7 @@ typedef int (*git_filter_stream_fn)(
  * allocated a `payload` to keep per-source filter state, use this
  * callback to free that payload and release resources as required.
  */
-typedef void (*git_filter_cleanup_fn)(
+typedef void GIT_CALLBACK(git_filter_cleanup_fn)(
 	git_filter *self,
 	void       *payload);
 
diff --git a/include/git2/sys/merge.h b/include/git2/sys/merge.h
index f07997d..bd0a8a4 100644
--- a/include/git2/sys/merge.h
+++ b/include/git2/sys/merge.h
@@ -73,7 +73,7 @@ GIT_EXTERN(const git_merge_file_options *) git_merge_driver_source_file_options(
  * initialization operations (in case libgit2 is being used in a way that
  * doesn't need the merge driver).
  */
-typedef int (*git_merge_driver_init_fn)(git_merge_driver *self);
+typedef int GIT_CALLBACK(git_merge_driver_init_fn)(git_merge_driver *self);
 
 /**
  * Shutdown callback on merge driver
@@ -85,7 +85,7 @@ typedef int (*git_merge_driver_init_fn)(git_merge_driver *self);
  *
  * Typically this function will free the `git_merge_driver` object itself.
  */
-typedef void (*git_merge_driver_shutdown_fn)(git_merge_driver *self);
+typedef void GIT_CALLBACK(git_merge_driver_shutdown_fn)(git_merge_driver *self);
 
 /**
  * Callback to perform the merge.
@@ -105,7 +105,7 @@ typedef void (*git_merge_driver_shutdown_fn)(git_merge_driver *self);
  *
  * The `src` contains the data about the file to be merged.
  */
-typedef int (*git_merge_driver_apply_fn)(
+typedef int GIT_CALLBACK(git_merge_driver_apply_fn)(
 	git_merge_driver *self,
 	const char **path_out,
 	uint32_t *mode_out,
diff --git a/include/git2/sys/odb_backend.h b/include/git2/sys/odb_backend.h
index 75341e8..1a74757 100644
--- a/include/git2/sys/odb_backend.h
+++ b/include/git2/sys/odb_backend.h
@@ -32,37 +32,37 @@ struct git_odb_backend {
 	 * will be freed later. The buffer should be allocated using
 	 * the function git_odb_backend_malloc to ensure that it can
 	 * be safely freed later. */
-	int (* read)(
+	int GIT_CALLBACK(read)(
 		void **, size_t *, git_object_t *, git_odb_backend *, const git_oid *);
 
 	/* To find a unique object given a prefix of its oid.  The oid given
 	 * must be so that the remaining (GIT_OID_HEXSZ - len)*4 bits are 0s.
 	 */
-	int (* read_prefix)(
+	int GIT_CALLBACK(read_prefix)(
 		git_oid *, void **, size_t *, git_object_t *,
 		git_odb_backend *, const git_oid *, size_t);
 
-	int (* read_header)(
+	int GIT_CALLBACK(read_header)(
 		size_t *, git_object_t *, git_odb_backend *, const git_oid *);
 
 	/**
 	 * Write an object into the backend. The id of the object has
 	 * already been calculated and is passed in.
 	 */
-	int (* write)(
+	int GIT_CALLBACK(write)(
 		git_odb_backend *, const git_oid *, const void *, size_t, git_object_t);
 
-	int (* writestream)(
+	int GIT_CALLBACK(writestream)(
 		git_odb_stream **, git_odb_backend *, git_off_t, git_object_t);
 
-	int (* readstream)(
+	int GIT_CALLBACK(readstream)(
 		git_odb_stream **, size_t *, git_object_t *,
 		git_odb_backend *, const git_oid *);
 
-	int (* exists)(
+	int GIT_CALLBACK(exists)(
 		git_odb_backend *, const git_oid *);
 
-	int (* exists_prefix)(
+	int GIT_CALLBACK(exists_prefix)(
 		git_oid *, git_odb_backend *, const git_oid *, size_t);
 
 	/**
@@ -75,12 +75,12 @@ struct git_odb_backend {
 	 * implementation to achieve this could be to internally invoke this
 	 * endpoint on failed lookups (ie. `exists()`, `read()`, `read_header()`).
 	 */
-	int (* refresh)(git_odb_backend *);
+	int GIT_CALLBACK(refresh)(git_odb_backend *);
 
-	int (* foreach)(
+	int GIT_CALLBACK(foreach)(
 		git_odb_backend *, git_odb_foreach_cb cb, void *payload);
 
-	int (* writepack)(
+	int GIT_CALLBACK(writepack)(
 		git_odb_writepack **, git_odb_backend *, git_odb *odb,
 		git_transfer_progress_cb progress_cb, void *progress_payload);
 
@@ -93,13 +93,13 @@ struct git_odb_backend {
 	 * If callers implement this, they should return `0` if the object
 	 * exists and was freshened, and non-zero otherwise.
 	 */
-	int (* freshen)(git_odb_backend *, const git_oid *);
+	int GIT_CALLBACK(freshen)(git_odb_backend *, const git_oid *);
 
 	/**
 	 * Frees any resources held by the odb (including the `git_odb_backend`
 	 * itself). An odb backend implementation must provide this function.
 	 */
-	void (* free)(git_odb_backend *);
+	void GIT_CALLBACK(free)(git_odb_backend *);
 };
 
 #define GIT_ODB_BACKEND_VERSION 1
diff --git a/include/git2/sys/refdb_backend.h b/include/git2/sys/refdb_backend.h
index 5129ad8..2ed6efd 100644
--- a/include/git2/sys/refdb_backend.h
+++ b/include/git2/sys/refdb_backend.h
@@ -38,21 +38,21 @@ struct git_reference_iterator {
 	/**
 	 * Return the current reference and advance the iterator.
 	 */
-	int (*next)(
+	int GIT_CALLBACK(next)(
 		git_reference **ref,
 		git_reference_iterator *iter);
 
 	/**
 	 * Return the name of the current reference and advance the iterator
 	 */
-	int (*next_name)(
+	int GIT_CALLBACK(next_name)(
 		const char **ref_name,
 		git_reference_iterator *iter);
 
 	/**
 	 * Free the iterator
 	 */
-	void (*free)(
+	void GIT_CALLBACK(free)(
 		git_reference_iterator *iter);
 };
 
@@ -64,7 +64,7 @@ struct git_refdb_backend {
 	 * Queries the refdb backend to determine if the given ref_name
 	 * exists.  A refdb implementation must provide this function.
 	 */
-	int (*exists)(
+	int GIT_CALLBACK(exists)(
 		int *exists,
 		git_refdb_backend *backend,
 		const char *ref_name);
@@ -73,7 +73,7 @@ struct git_refdb_backend {
 	 * Queries the refdb backend for a given reference.  A refdb
 	 * implementation must provide this function.
 	 */
-	int (*lookup)(
+	int GIT_CALLBACK(lookup)(
 		git_reference **out,
 		git_refdb_backend *backend,
 		const char *ref_name);
@@ -83,7 +83,7 @@ struct git_refdb_backend {
 	 *
 	 * A refdb implementation must provide this function.
 	 */
-	int (*iterator)(
+	int GIT_CALLBACK(iterator)(
 		git_reference_iterator **iter,
 		struct git_refdb_backend *backend,
 		const char *glob);
@@ -92,12 +92,12 @@ struct git_refdb_backend {
 	 * Writes the given reference to the refdb.  A refdb implementation
 	 * must provide this function.
 	 */
-	int (*write)(git_refdb_backend *backend,
+	int GIT_CALLBACK(write)(git_refdb_backend *backend,
 		     const git_reference *ref, int force,
 		     const git_signature *who, const char *message,
 		     const git_oid *old, const char *old_target);
 
-	int (*rename)(
+	int GIT_CALLBACK(rename)(
 		git_reference **out, git_refdb_backend *backend,
 		const char *old_name, const char *new_name, int force,
 		const git_signature *who, const char *message);
@@ -107,7 +107,7 @@ struct git_refdb_backend {
 	 * from the refdb.  A refdb implementation must provide this
 	 * function.
 	 */
-	int (*del)(git_refdb_backend *backend, const char *ref_name, const git_oid *old_id, const char *old_target);
+	int GIT_CALLBACK(del)(git_refdb_backend *backend, const char *ref_name, const git_oid *old_id, const char *old_target);
 
 	/**
 	 * Suggests that the given refdb compress or optimize its references.
@@ -116,56 +116,56 @@ struct git_refdb_backend {
 	 * implementation may provide this function; if it is not provided,
 	 * nothing will be done.
 	 */
-	int (*compress)(git_refdb_backend *backend);
+	int GIT_CALLBACK(compress)(git_refdb_backend *backend);
 
 	/**
 	 * Query whether a particular reference has a log (may be empty)
 	 */
-	int (*has_log)(git_refdb_backend *backend, const char *refname);
+	int GIT_CALLBACK(has_log)(git_refdb_backend *backend, const char *refname);
 
 	/**
 	 * Make sure a particular reference will have a reflog which
 	 * will be appended to on writes.
 	 */
-	int (*ensure_log)(git_refdb_backend *backend, const char *refname);
+	int GIT_CALLBACK(ensure_log)(git_refdb_backend *backend, const char *refname);
 
 	/**
 	 * Frees any resources held by the refdb (including the `git_refdb_backend`
 	 * itself). A refdb backend implementation must provide this function.
 	 */
-	void (*free)(git_refdb_backend *backend);
+	void GIT_CALLBACK(free)(git_refdb_backend *backend);
 
 	/**
 	 * Read the reflog for the given reference name.
 	 */
-	int (*reflog_read)(git_reflog **out, git_refdb_backend *backend, const char *name);
+	int GIT_CALLBACK(reflog_read)(git_reflog **out, git_refdb_backend *backend, const char *name);
 
 	/**
 	 * Write a reflog to disk.
 	 */
-	int (*reflog_write)(git_refdb_backend *backend, git_reflog *reflog);
+	int GIT_CALLBACK(reflog_write)(git_refdb_backend *backend, git_reflog *reflog);
 
 	/**
 	 * Rename a reflog
 	 */
-	int (*reflog_rename)(git_refdb_backend *_backend, const char *old_name, const char *new_name);
+	int GIT_CALLBACK(reflog_rename)(git_refdb_backend *_backend, const char *old_name, const char *new_name);
 
 	/**
 	 * Remove a reflog.
 	 */
-	int (*reflog_delete)(git_refdb_backend *backend, const char *name);
+	int GIT_CALLBACK(reflog_delete)(git_refdb_backend *backend, const char *name);
 
 	/**
 	 * Lock a reference. The opaque parameter will be passed to the unlock function
 	 */
-	int (*lock)(void **payload_out, git_refdb_backend *backend, const char *refname);
+	int GIT_CALLBACK(lock)(void **payload_out, git_refdb_backend *backend, const char *refname);
 
 	/**
 	 * Unlock a reference. Only one of target or symbolic_target
 	 * will be set. success indicates whether to update the
 	 * reference or discard the lock (if it's false)
 	 */
-	int (*unlock)(git_refdb_backend *backend, void *payload, int success, int update_reflog,
+	int GIT_CALLBACK(unlock)(git_refdb_backend *backend, void *payload, int success, int update_reflog,
 		      const git_reference *ref, const git_signature *sig, const char *message);
 };
 
diff --git a/include/git2/sys/stream.h b/include/git2/sys/stream.h
index 9387931..255c93e 100644
--- a/include/git2/sys/stream.h
+++ b/include/git2/sys/stream.h
@@ -31,13 +31,13 @@ typedef struct git_stream {
 
 	int encrypted;
 	int proxy_support;
-	int (*connect)(struct git_stream *);
-	int (*certificate)(git_cert **, struct git_stream *);
-	int (*set_proxy)(struct git_stream *, const git_proxy_options *proxy_opts);
-	ssize_t (*read)(struct git_stream *, void *, size_t);
-	ssize_t (*write)(struct git_stream *, const char *, size_t, int);
-	int (*close)(struct git_stream *);
-	void (*free)(struct git_stream *);
+	int GIT_CALLBACK(connect)(struct git_stream *);
+	int GIT_CALLBACK(certificate)(git_cert **, struct git_stream *);
+	int GIT_CALLBACK(set_proxy)(struct git_stream *, const git_proxy_options *proxy_opts);
+	ssize_t GIT_CALLBACK(read)(struct git_stream *, void *, size_t);
+	ssize_t GIT_CALLBACK(write)(struct git_stream *, const char *, size_t, int);
+	int GIT_CALLBACK(close)(struct git_stream *);
+	void GIT_CALLBACK(free)(struct git_stream *);
 } git_stream;
 
 typedef struct {
@@ -54,7 +54,7 @@ typedef struct {
 	 *             service name
 	 * @return 0 or an error code
 	 */
-	int (*init)(git_stream **out, const char *host, const char *port);
+	int GIT_CALLBACK(init)(git_stream **out, const char *host, const char *port);
 
 	/**
 	 * Called to create a new connection on top of the given stream.  If
@@ -68,7 +68,7 @@ typedef struct {
 	 *             for certificate validation
 	 * @return 0 or an error code
 	 */
-	int (*wrap)(git_stream **out, git_stream *in, const char *host);
+	int GIT_CALLBACK(wrap)(git_stream **out, git_stream *in, const char *host);
 } git_stream_registration;
 
 /**
@@ -111,7 +111,7 @@ GIT_EXTERN(int) git_stream_register(
  * @deprecated Provide a git_stream_registration to git_stream_register
  * @see git_stream_registration
  */
-typedef int (*git_stream_cb)(git_stream **out, const char *host, const char *port);
+typedef int GIT_CALLBACK(git_stream_cb)(git_stream **out, const char *host, const char *port);
 
 /**
  * Register a TLS stream constructor for the library to use.  This stream
diff --git a/include/git2/sys/transport.h b/include/git2/sys/transport.h
index aac6f9f..92cb32b 100644
--- a/include/git2/sys/transport.h
+++ b/include/git2/sys/transport.h
@@ -35,7 +35,7 @@ typedef enum {
 struct git_transport {
 	unsigned int version;
 	/* Set progress and error callbacks */
-	int (*set_callbacks)(
+	int GIT_CALLBACK(set_callbacks)(
 		git_transport *transport,
 		git_transport_message_cb progress_cb,
 		git_transport_message_cb error_cb,
@@ -43,13 +43,13 @@ struct git_transport {
 		void *payload);
 
 	/* Set custom headers for HTTP requests */
-	int (*set_custom_headers)(
+	int GIT_CALLBACK(set_custom_headers)(
 		git_transport *transport,
 		const git_strarray *custom_headers);
 
 	/* Connect the transport to the remote repository, using the given
 	 * direction. */
-	int (*connect)(
+	int GIT_CALLBACK(connect)(
 		git_transport *transport,
 		const char *url,
 		git_cred_acquire_cb cred_acquire_cb,
@@ -61,18 +61,18 @@ struct git_transport {
 	/* This function may be called after a successful call to
 	 * connect(). The array returned is owned by the transport and
 	 * is guaranteed until the next call of a transport function. */
-	int (*ls)(
+	int GIT_CALLBACK(ls)(
 		const git_remote_head ***out,
 		size_t *size,
 		git_transport *transport);
 
 	/* Executes the push whose context is in the git_push object. */
-	int(*push)(git_transport *transport, git_push *push, const git_remote_callbacks *callbacks);
+	int GIT_CALLBACK(push)(git_transport *transport, git_push *push, const git_remote_callbacks *callbacks);
 
 	/* This function may be called after a successful call to connect(), when
 	 * the direction is FETCH. The function performs a negotiation to calculate
 	 * the wants list for the fetch. */
-	int (*negotiate_fetch)(
+	int GIT_CALLBACK(negotiate_fetch)(
 		git_transport *transport,
 		git_repository *repo,
 		const git_remote_head * const *refs,
@@ -81,7 +81,7 @@ struct git_transport {
 	/* This function may be called after a successful call to negotiate_fetch(),
 	 * when the direction is FETCH. This function retrieves the pack file for
 	 * the fetch from the remote end. */
-	int (*download_pack)(
+	int GIT_CALLBACK(download_pack)(
 		git_transport *transport,
 		git_repository *repo,
 		git_transfer_progress *stats,
@@ -89,20 +89,20 @@ struct git_transport {
 		void *progress_payload);
 
 	/* Checks to see if the transport is connected */
-	int (*is_connected)(git_transport *transport);
+	int GIT_CALLBACK(is_connected)(git_transport *transport);
 
 	/* Reads the flags value previously passed into connect() */
-	int (*read_flags)(git_transport *transport, int *flags);
+	int GIT_CALLBACK(read_flags)(git_transport *transport, int *flags);
 
 	/* Cancels any outstanding transport operation */
-	void (*cancel)(git_transport *transport);
+	void GIT_CALLBACK(cancel)(git_transport *transport);
 
 	/* This function is the reverse of connect() -- it terminates the
 	 * connection to the remote end. */
-	int (*close)(git_transport *transport);
+	int GIT_CALLBACK(close)(git_transport *transport);
 
 	/* Frees/destructs the git_transport object. */
-	void (*free)(git_transport *transport);
+	void GIT_CALLBACK(free)(git_transport *transport);
 };
 
 #define GIT_TRANSPORT_VERSION 1
@@ -292,25 +292,25 @@ struct git_smart_subtransport_stream {
 	/* The owning subtransport */
 	git_smart_subtransport *subtransport;
 
-	int (*read)(
+	int GIT_CALLBACK(read)(
 		git_smart_subtransport_stream *stream,
 		char *buffer,
 		size_t buf_size,
 		size_t *bytes_read);
 
-	int (*write)(
+	int GIT_CALLBACK(write)(
 		git_smart_subtransport_stream *stream,
 		const char *buffer,
 		size_t len);
 
-	void (*free)(
+	void GIT_CALLBACK(free)(
 		git_smart_subtransport_stream *stream);
 };
 
 /* An implementation of a subtransport which carries data for the
  * smart transport */
 struct git_smart_subtransport {
-	int (* action)(
+	int GIT_CALLBACK(action)(
 			git_smart_subtransport_stream **out,
 			git_smart_subtransport *transport,
 			const char *url,
@@ -322,13 +322,13 @@ struct git_smart_subtransport {
 	 *
 	 * 1. UPLOADPACK_LS -> UPLOADPACK
 	 * 2. RECEIVEPACK_LS -> RECEIVEPACK */
-	int (*close)(git_smart_subtransport *transport);
+	int GIT_CALLBACK(close)(git_smart_subtransport *transport);
 
-	void (*free)(git_smart_subtransport *transport);
+	void GIT_CALLBACK(free)(git_smart_subtransport *transport);
 };
 
 /* A function which creates a new subtransport for the smart transport */
-typedef int (*git_smart_subtransport_cb)(
+typedef int GIT_CALLBACK(git_smart_subtransport_cb)(
 	git_smart_subtransport **out,
 	git_transport* owner,
 	void* param);
diff --git a/include/git2/tag.h b/include/git2/tag.h
index 12683e4..1ca3348 100644
--- a/include/git2/tag.h
+++ b/include/git2/tag.h
@@ -318,7 +318,7 @@ GIT_EXTERN(int) git_tag_list_match(
 	git_repository *repo);
 
 
-typedef int (*git_tag_foreach_cb)(const char *name, git_oid *oid, void *payload);
+typedef int GIT_CALLBACK(git_tag_foreach_cb)(const char *name, git_oid *oid, void *payload);
 
 /**
  * Call callback `cb' for each tag in the repository
diff --git a/include/git2/trace.h b/include/git2/trace.h
index f9b4d6f..f8bbfb2 100644
--- a/include/git2/trace.h
+++ b/include/git2/trace.h
@@ -49,7 +49,7 @@ typedef enum {
 /**
  * An instance for a tracing function
  */
-typedef void (*git_trace_callback)(git_trace_level_t level, const char *msg);
+typedef void GIT_CALLBACK(git_trace_callback)(git_trace_level_t level, const char *msg);
 
 /**
  * Sets the system tracing configuration to the specified level with the
diff --git a/include/git2/transport.h b/include/git2/transport.h
index 9264251..2ba2d7e 100644
--- a/include/git2/transport.h
+++ b/include/git2/transport.h
@@ -21,7 +21,7 @@
 GIT_BEGIN_DECL
 
 /** Signature of a function which creates a transport */
-typedef int (*git_transport_cb)(git_transport **out, git_remote *owner, void *param);
+typedef int GIT_CALLBACK(git_transport_cb)(git_transport **out, git_remote *owner, void *param);
 
 /**
  * Type of SSH host fingerprint
@@ -144,7 +144,7 @@ typedef struct git_cred git_cred;
  */
 struct git_cred {
 	git_credtype_t credtype; /**< A type of credential */
-	void (*free)(git_cred *cred);
+	void GIT_CALLBACK(free)(git_cred *cred);
 };
 
 /** A plaintext username and password */
@@ -165,8 +165,8 @@ typedef struct _LIBSSH2_USERAUTH_KBDINT_PROMPT LIBSSH2_USERAUTH_KBDINT_PROMPT;
 typedef struct _LIBSSH2_USERAUTH_KBDINT_RESPONSE LIBSSH2_USERAUTH_KBDINT_RESPONSE;
 #endif
 
-typedef int (*git_cred_sign_callback)(LIBSSH2_SESSION *session, unsigned char **sig, size_t *sig_len, const unsigned char *data, size_t data_len, void **abstract);
-typedef void (*git_cred_ssh_interactive_callback)(const char* name, int name_len, const char* instruction, int instruction_len, int num_prompts, const LIBSSH2_USERAUTH_KBDINT_PROMPT* prompts, LIBSSH2_USERAUTH_KBDINT_RESPONSE* responses, void **abstract);
+typedef int GIT_CALLBACK(git_cred_sign_callback)(LIBSSH2_SESSION *session, unsigned char **sig, size_t *sig_len, const unsigned char *data, size_t data_len, void **abstract);
+typedef void GIT_CALLBACK(git_cred_ssh_interactive_callback)(const char* name, int name_len, const char* instruction, int instruction_len, int num_prompts, const LIBSSH2_USERAUTH_KBDINT_PROMPT* prompts, LIBSSH2_USERAUTH_KBDINT_RESPONSE* responses, void **abstract);
 
 /**
  * A ssh key from disk
@@ -359,7 +359,7 @@ GIT_EXTERN(void) git_cred_free(git_cred *cred);
  * @return 0 for success, < 0 to indicate an error, > 0 to indicate
  *       no credential was acquired
  */
-typedef int (*git_cred_acquire_cb)(
+typedef int GIT_CALLBACK(git_cred_acquire_cb)(
 	git_cred **cred,
 	const char *url,
 	const char *username_from_url,
diff --git a/include/git2/tree.h b/include/git2/tree.h
index e98a4c6..aca5d75 100644
--- a/include/git2/tree.h
+++ b/include/git2/tree.h
@@ -344,7 +344,7 @@ GIT_EXTERN(int) git_treebuilder_remove(
  * entry should be left alone and any non-zero value meaning that the
  * entry should be removed from the treebuilder list (i.e. filtered out).
  */
-typedef int (*git_treebuilder_filter_cb)(
+typedef int GIT_CALLBACK(git_treebuilder_filter_cb)(
 	const git_tree_entry *entry, void *payload);
 
 /**
@@ -391,7 +391,7 @@ GIT_EXTERN(int) git_treebuilder_write_with_buffer(
 	git_oid *oid, git_treebuilder *bld, git_buf *tree);
 
 /** Callback for the tree traversal method */
-typedef int (*git_treewalk_cb)(
+typedef int GIT_CALLBACK(git_treewalk_cb)(
 	const char *root, const git_tree_entry *entry, void *payload);
 
 /** Tree traversal modes */
diff --git a/include/git2/types.h b/include/git2/types.h
index 2074ca9..a9c2865 100644
--- a/include/git2/types.h
+++ b/include/git2/types.h
@@ -272,7 +272,7 @@ typedef struct git_transfer_progress {
  * @param stats Structure containing information about the state of the transfer
  * @param payload Payload provided by caller
  */
-typedef int (*git_transfer_progress_cb)(const git_transfer_progress *stats, void *payload);
+typedef int GIT_CALLBACK(git_transfer_progress_cb)(const git_transfer_progress *stats, void *payload);
 
 /**
  * Type for messages delivered by the transport.  Return a negative value
@@ -282,7 +282,7 @@ typedef int (*git_transfer_progress_cb)(const git_transfer_progress *stats, void
  * @param len The length of the message
  * @param payload Payload provided by the caller
  */
-typedef int (*git_transport_message_cb)(const char *str, int len, void *payload);
+typedef int GIT_CALLBACK(git_transport_message_cb)(const char *str, int len, void *payload);
 
 
 /**
@@ -335,7 +335,7 @@ typedef struct {
  *         or > 0 to indicate that the callback refused to act and that
  *         the existing validity determination should be honored
  */
-typedef int (*git_transport_certificate_check_cb)(git_cert *cert, int valid, const char *host, void *payload);
+typedef int GIT_CALLBACK(git_transport_certificate_check_cb)(git_cert *cert, int valid, const char *host, void *payload);
 
 /**
  * Opaque structure representing a submodule.
@@ -433,9 +433,9 @@ typedef struct git_writestream git_writestream;
 
 /** A type to write in a streaming fashion, for example, for filters. */
 struct git_writestream {
-	int (*write)(git_writestream *stream, const char *buffer, size_t len);
-	int (*close)(git_writestream *stream);
-	void (*free)(git_writestream *stream);
+	int GIT_CALLBACK(write)(git_writestream *stream, const char *buffer, size_t len);
+	int GIT_CALLBACK(close)(git_writestream *stream);
+	void GIT_CALLBACK(free)(git_writestream *stream);
 };
 
 /** Representation of .mailmap file state. */