alloc: simplify pluggable allocators

Remove the number of functions that custom allocator users need to
provide; nobody should need to implement `substrdup`. Keep it to the
basics that are actually _needed_ for allocation (malloc, realloc,
free) and reimplement the rest ourselves.

In addition, move the failure check and error setting _out_ of the
custom allocators and into a wrapper so that users don't need to deal
with this. This also allows us to call our allocator (without the
wrapper) early so that it does not try to set an error on failure, which
may be important for bootstrapping.

Author: ethomson

include/git2/sys/alloc.h

@@ -24,47 +24,13 @@ typedef struct {
 	/** Allocate `n` bytes of memory */
 	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 * 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 * 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 * 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 * 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 * 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 * 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 * 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.

src/util/alloc.c

@@ -15,16 +15,75 @@
 /* Fail any allocation until git_libgit2_init is called. */
 git_allocator git__allocator = {
 	git_failalloc_malloc,
-	git_failalloc_calloc,
-	git_failalloc_strdup,
-	git_failalloc_strndup,
-	git_failalloc_substrdup,
 	git_failalloc_realloc,
-	git_failalloc_reallocarray,
-	git_failalloc_mallocarray,
 	git_failalloc_free
 };
 
+void *git__calloc(size_t nelem, size_t elsize)
+{
+	size_t newsize;
+	void *ptr;
+
+	if (GIT_MULTIPLY_SIZET_OVERFLOW(&newsize, nelem, elsize))
+		return NULL;
+
+	if ((ptr = git__malloc(newsize)))
+		memset(ptr, 0, newsize);
+
+	return ptr;
+}
+
+void *git__reallocarray(void *ptr, size_t nelem, size_t elsize)
+{
+	size_t newsize;
+
+	if (GIT_MULTIPLY_SIZET_OVERFLOW(&newsize, nelem, elsize))
+		return NULL;
+
+	return git__realloc(ptr, newsize);
+}
+
+void *git__mallocarray(size_t nelem, size_t elsize)
+{
+	return git__reallocarray(NULL, nelem, elsize);
+}
+
+char *git__strdup(const char *str)
+{
+	size_t len = strlen(str) + 1;
+	void *ptr = git__malloc(len);
+
+	if (ptr)
+		memcpy(ptr, str, len);
+
+	return ptr;
+}
+
+char *git__strndup(const char *str, size_t n)
+{
+	size_t len = p_strnlen(str, n);
+	char *ptr = git__malloc(len + 1);
+
+	if (ptr) {
+		memcpy(ptr, str, len);
+		ptr[len] = '\0';
+	}
+
+	return ptr;
+}
+
+char *git__substrdup(const char *str, size_t n)
+{
+	char *ptr = git__malloc(n + 1);
+
+	if (ptr) {
+		memcpy(ptr, str, n);
+		ptr[n] = '\0';
+	}
+
+	return ptr;
+}
+
 static int setup_default_allocator(void)
 {
 #if defined(GIT_WIN32_LEAKCHECK)

src/util/alloc.h

@@ -10,17 +10,42 @@
 
 #include "git2/sys/alloc.h"
 
+#include "git2_util.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
+GIT_INLINE(void *) git__malloc(size_t len)
+{
+	void *p = git__allocator.gmalloc(len, __FILE__, __LINE__);
+
+	if (!p)
+		git_error_set_oom();
+
+	return p;
+}
+
+GIT_INLINE(void *) git__realloc(void *ptr, size_t size)
+{
+	void *p = git__allocator.grealloc(ptr, size, __FILE__, __LINE__);
+
+	if (!p)
+		git_error_set_oom();
+
+	return p;
+}
+
+GIT_INLINE(void) git__free(void *ptr)
+{
+	git__allocator.gfree(ptr);
+}
+
+extern void *git__calloc(size_t nelem, size_t elsize);
+extern void *git__mallocarray(size_t nelem, size_t elsize);
+extern void *git__reallocarray(void *ptr, size_t nelem, size_t elsize);
+
+extern char *git__strdup(const char *str);
+extern char *git__strndup(const char *str, size_t n);
+extern char *git__substrdup(const char *str, size_t n);
 
 /**
  * This function is being called by our global setup routines to

src/util/allocators/failalloc.c

@@ -16,45 +16,6 @@ void *git_failalloc_malloc(size_t len, const char *file, int line)
 	return NULL;
 }
 
-void *git_failalloc_calloc(size_t nelem, size_t elsize, const char *file, int line)
-{
-	GIT_UNUSED(nelem);
-	GIT_UNUSED(elsize);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
-char *git_failalloc_strdup(const char *str, const char *file, int line)
-{
-	GIT_UNUSED(str);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
-char *git_failalloc_strndup(const char *str, size_t n, const char *file, int line)
-{
-	GIT_UNUSED(str);
-	GIT_UNUSED(n);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
-char *git_failalloc_substrdup(const char *start, size_t n, const char *file, int line)
-{
-	GIT_UNUSED(start);
-	GIT_UNUSED(n);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
 void *git_failalloc_realloc(void *ptr, size_t size, const char *file, int line)
 {
 	GIT_UNUSED(ptr);
@@ -65,27 +26,6 @@ void *git_failalloc_realloc(void *ptr, size_t size, const char *file, int line)
 	return NULL;
 }
 
-void *git_failalloc_reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line)
-{
-	GIT_UNUSED(ptr);
-	GIT_UNUSED(nelem);
-	GIT_UNUSED(elsize);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
-void *git_failalloc_mallocarray(size_t nelem, size_t elsize, const char *file, int line)
-{
-	GIT_UNUSED(nelem);
-	GIT_UNUSED(elsize);
-	GIT_UNUSED(file);
-	GIT_UNUSED(line);
-
-	return NULL;
-}
-
 void git_failalloc_free(void *ptr)
 {
 	GIT_UNUSED(ptr);

src/util/allocators/failalloc.h

@@ -11,13 +11,7 @@
 #include "git2_util.h"
 
 extern void *git_failalloc_malloc(size_t len, const char *file, int line);
-extern void *git_failalloc_calloc(size_t nelem, size_t elsize, const char *file, int line);
-extern char *git_failalloc_strdup(const char *str, const char *file, int line);
-extern char *git_failalloc_strndup(const char *str, size_t n, const char *file, int line);
-extern char *git_failalloc_substrdup(const char *start, size_t n, const char *file, int line);
 extern void *git_failalloc_realloc(void *ptr, size_t size, const char *file, int line);
-extern void *git_failalloc_reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line);
-extern void *git_failalloc_mallocarray(size_t nelem, size_t elsize, const char *file, int line);
 extern void git_failalloc_free(void *ptr);
 
 #endif