Merge pull request libgit2#4576 from pks-t/pks/memory-allocator

Custom memory allocators

Author: pks-t

CHANGELOG.md

@@ -13,6 +13,9 @@ v0.27 + 1
 
 ### API additions
 
+* You can now swap out memory allocators via the
+  `GIT_OPT_SET_ALLOCATOR` option with `git_libgit2_opts()`.
+
 ### API removals
 
 ### Breaking API changes

include/git2/common.h

@@ -183,6 +183,7 @@ typedef enum {
 	GIT_OPT_GET_WINDOWS_SHAREMODE,
 	GIT_OPT_SET_WINDOWS_SHAREMODE,
 	GIT_OPT_ENABLE_STRICT_HASH_VERIFICATION,
+	GIT_OPT_SET_ALLOCATOR
 } git_libgit2_opt_t;
 
 /**
@@ -345,6 +346,12 @@ typedef enum {
  *		> additional checksum calculation on each object. This defaults
  *		> to enabled.
  *
+ *	 opts(GIT_OPT_SET_ALLOCATOR, git_allocator *allocator)
+ *
+ *		> Set the memory allocator to a different memory allocator. This
+ *		> allocator will then be used to make all memory allocations for
+ *		> libgit2 operations.
+ *
  * @param option Option key
  * @param ... value to set the option
  * @return 0 on success, <0 on failure

include/git2/sys/alloc.h

@@ -0,0 +1,101 @@
+/*
+ * 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_sys_git_alloc_h__
+#define INCLUDE_sys_git_alloc_h__
+
+#include "git2/common.h"
+
+GIT_BEGIN_DECL
+
+/**
+ * An instance for a custom memory allocator
+ *
+ * Setting the pointers of this structure allows the developer to implement
+ * custom memory allocators. The global memory allocator can be set by using
+ * "GIT_OPT_SET_ALLOCATOR" with the `git_libgit2_opts` function. Keep in mind
+ * that all fields need to be set to a proper function.
+ */
+typedef struct {
+	/* Allocate `n` bytes of memory */
+	void *(*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);
+
+	/* Allocate memory for the string `str` and duplicate its contents. */
+	char *(*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);
+
+	/*
+	 * 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);
+
+	/*
+	 * 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);
+
+	/*
+	 * 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);
+
+	/*
+	 * 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);
+
+	/*
+	 * 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);
+} git_allocator;
+
+/**
+ * Initialize the allocator structure to use the `stdalloc` pointer.
+ *
+ * Set up the structure so that all of its members are using the standard
+ * "stdalloc" allocator functions. The structure can then be used with
+ * `git_allocator_setup`.
+ *
+ * @param allocator The allocator that is to be initialized.
+ * @return An error code or 0.
+ */
+int git_stdalloc_init_allocator(git_allocator *allocator);
+
+/**
+ * Initialize the allocator structure to use the `crtdbg` pointer.
+ *
+ * Set up the structure so that all of its members are using the "crtdbg"
+ * allocator functions. Note that this allocator is only available on Windows
+ * platforms and only if libgit2 is being compiled with "-DMSVC_CRTDBG".
+ *
+ * @param allocator The allocator that is to be initialized.
+ * @return An error code or 0.
+ */
+int git_win32_crtdbg_init_allocator(git_allocator *allocator);
+
+GIT_END_DECL
+
+#endif

src/alloc.c

@@ -0,0 +1,40 @@
+/*
+ * 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.
+ */
+
+#include "alloc.h"
+
+#if defined(GIT_MSVC_CRTDBG)
+# include "win32/w32_crtdbg_stacktrace.h"
+#else
+# include "stdalloc.h"
+#endif
+
+git_allocator git__allocator;
+
+int git_allocator_global_init(void)
+{
+#if defined(GIT_MSVC_CRTDBG)
+	return git_win32_crtdbg_init_allocator(&git__allocator);
+#else
+	return git_stdalloc_init_allocator(&git__allocator);
+#endif
+}
+
+int git_allocator_setup(git_allocator *allocator)
+{
+	memcpy(&git__allocator, allocator, sizeof(*allocator));
+	return 0;
+}
+
+#if !defined(GIT_MSVC_CRTDBG)
+int git_win32_crtdbg_init_allocator(git_allocator *allocator)
+{
+	GIT_UNUSED(allocator);
+	giterr_set(GIT_EINVALID, "crtdbg memory allocator not available");
+	return -1;
+}
+#endif

src/alloc.h

@@ -0,0 +1,40 @@
+/*
+ * 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_alloc_h__
+#define INCLUDE_alloc_h__
+
+#include "git2/sys/alloc.h"
+
+extern git_allocator git__allocator;
+
+#define git__malloc(len)                      git__allocator.gmalloc(len, __FILE__, __LINE__)
+#define git__calloc(nelem, elsize)            git__allocator.gcalloc(nelem, elsize, __FILE__, __LINE__)
+#define git__strdup(str)                      git__allocator.gstrdup(str, __FILE__, __LINE__)
+#define git__strndup(str, n)                  git__allocator.gstrndup(str, n, __FILE__, __LINE__)
+#define git__substrdup(str, n)                git__allocator.gsubstrdup(str, n, __FILE__, __LINE__)
+#define git__realloc(ptr, size)               git__allocator.grealloc(ptr, size, __FILE__, __LINE__)
+#define git__reallocarray(ptr, nelem, elsize) git__allocator.greallocarray(ptr, nelem, elsize, __FILE__, __LINE__)
+#define git__mallocarray(nelem, elsize)       git__allocator.gmallocarray(nelem, elsize, __FILE__, __LINE__)
+#define git__free                             git__allocator.gfree
+
+/**
+ * This function is being called by our global setup routines to
+ * initialize the standard allocator.
+ */
+int git_allocator_global_init(void);
+
+/**
+ * Switch out libgit2's global memory allocator
+ *
+ * @param allocator The new allocator that should be used. All function pointers
+ *                  of it need to be set correctly.
+ * @return An error code or 0.
+ */
+int git_allocator_setup(git_allocator *allocator);
+
+#endif

src/global.c

@@ -7,6 +7,7 @@
 
 #include "global.h"
 
+#include "alloc.h"
 #include "hash.h"
 #include "sysdir.h"
 #include "filter.h"
@@ -60,7 +61,8 @@ static int init_common(void)
 #endif
 
 	/* Initialize any other subsystems that have global state */
-	if ((ret = git_hash_global_init()) == 0 &&
+	if ((ret = git_allocator_global_init()) == 0 &&
+		(ret = git_hash_global_init()) == 0 &&
 		(ret = git_sysdir_global_init()) == 0 &&
 		(ret = git_filter_global_init()) == 0 &&
 		(ret = git_merge_driver_global_init()) == 0 &&

src/settings.c

@@ -16,6 +16,7 @@
 #endif
 
 #include <git2.h>
+#include "alloc.h"
 #include "sysdir.h"
 #include "cache.h"
 #include "global.h"
@@ -260,6 +261,10 @@ int git_libgit2_opts(int key, ...)
 		git_odb__strict_hash_verification = (va_arg(ap, int) != 0);
 		break;
 
+	case GIT_OPT_SET_ALLOCATOR:
+		error = git_allocator_setup(va_arg(ap, git_allocator *));
+		break;
+
 	default:
 		giterr_set(GITERR_INVALID, "invalid option key");
 		error = -1;

src/stdalloc.c

@@ -0,0 +1,120 @@
+/*
+ * 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.
+ */
+
+#include "stdalloc.h"
+
+static void *stdalloc__malloc(size_t len, const char *file, int line)
+{
+	void *ptr = malloc(len);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!ptr) giterr_set_oom();
+	return ptr;
+}
+
+static void *stdalloc__calloc(size_t nelem, size_t elsize, const char *file, int line)
+{
+	void *ptr = calloc(nelem, elsize);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!ptr) giterr_set_oom();
+	return ptr;
+}
+
+static char *stdalloc__strdup(const char *str, const char *file, int line)
+{
+	char *ptr = strdup(str);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!ptr) giterr_set_oom();
+	return ptr;
+}
+
+static char *stdalloc__strndup(const char *str, size_t n, const char *file, int line)
+{
+	size_t length = 0, alloclength;
+	char *ptr;
+
+	length = p_strnlen(str, n);
+
+	if (GIT_ADD_SIZET_OVERFLOW(&alloclength, length, 1) ||
+		!(ptr = stdalloc__malloc(alloclength, file, line)))
+		return NULL;
+
+	if (length)
+		memcpy(ptr, str, length);
+
+	ptr[length] = '\0';
+
+	return ptr;
+}
+
+static char *stdalloc__substrdup(const char *start, size_t n, const char *file, int line)
+{
+	char *ptr;
+	size_t alloclen;
+
+	if (GIT_ADD_SIZET_OVERFLOW(&alloclen, n, 1) ||
+		!(ptr = stdalloc__malloc(alloclen, file, line)))
+		return NULL;
+
+	memcpy(ptr, start, n);
+	ptr[n] = '\0';
+	return ptr;
+}
+
+static void *stdalloc__realloc(void *ptr, size_t size, const char *file, int line)
+{
+	void *new_ptr = realloc(ptr, size);
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	if (!new_ptr) giterr_set_oom();
+	return new_ptr;
+}
+
+static void *stdalloc__reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line)
+{
+	size_t newsize;
+
+	GIT_UNUSED(file);
+	GIT_UNUSED(line);
+
+	return GIT_MULTIPLY_SIZET_OVERFLOW(&newsize, nelem, elsize) ?
+		NULL : realloc(ptr, newsize);
+}
+
+static void *stdalloc__mallocarray(size_t nelem, size_t elsize, const char *file, int line)
+{
+	return stdalloc__reallocarray(NULL, nelem, elsize, file, line);
+}
+
+static void stdalloc__free(void *ptr)
+{
+	free(ptr);
+}
+
+int git_stdalloc_init_allocator(git_allocator *allocator)
+{
+	allocator->gmalloc = stdalloc__malloc;
+	allocator->gcalloc = stdalloc__calloc;
+	allocator->gstrdup = stdalloc__strdup;
+	allocator->gstrndup = stdalloc__strndup;
+	allocator->gsubstrdup = stdalloc__substrdup;
+	allocator->grealloc = stdalloc__realloc;
+	allocator->greallocarray = stdalloc__reallocarray;
+	allocator->gmallocarray = stdalloc__mallocarray;
+	allocator->gfree = stdalloc__free;
+	return 0;
+}

src/stdalloc.h

@@ -0,0 +1,17 @@
+/*
+ * 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_stdalloc_h__
+#define INCLUDE_stdalloc_h__
+
+#include "alloc.h"
+
+#include "common.h"
+
+int git_stdalloc_init_allocator(git_allocator *allocator);
+
+#endif