stdalloc: extend allocators by file and line

Our desired architecture would make allocators completely pluggable,
such that users of libgit2 can swap out memory allocators at runtime.
While making e.g. debugging easier by not having to do a separate build,
this feature can also help maintainers of bindings for libgit2 by tying
the memory allocations into the other language's memory system.

In order to do so, though, we first need to make our two different
pre-existing allocators "stdalloc" and "crtdbg" have the same function
signatures, as the "crtdbg" allocators all have an additional file and
line argument. This is required to build correct stack traces for
debugging memory allocations. As that feature may also be interesting to
authors of other applications for debugging libgit2, we now simply add
these arguments to our standard allocators.

Obviously, this may come with a performance penalty. During some simple
benchmarks no real impact could be measured though in contrast to a
simple pluggable allocator. The following table summarizes the
benchmarks. There were three different builds with our current standard
allocator ("standard"), with pluggable authenticators accessed via
function pointers ("pluggable") and for pluggable authenticators with
file and line being added ("fileline"). Furthermore, there were three
scenarios for 100.000.000 allocations of 100B ("small alloc"),
100.000.000 allocations of 100KB ("medium alloc"), and 1.000.000
allocations of 100MB. All results are best of 10 runs.

|------------|-------------------|-------------------|-------------------|
| build/test | small alloc       | medium alloc      | big alloc         |
|------------|-------------------|-------------------|-------------------|
| standard   | 4539779566, +0.0% | 5912927186, +0.0% | 5166935308, +0.0% |
|------------|-------------------|-------------------|-------------------|
| pluggable  | 4611074505, +1.5% | 5979185308, +1.1% | 5388776352, +4.2% |
|------------|-------------------|-------------------|-------------------|
| fileline   | 4588338192, +1.1% | 6004951910, +1.5% | 4942528135, -4.4% |
|------------|-------------------|-------------------|-------------------|

As can be seen, there is a performance overhead for pluggable
allocators. Furthermore, it can also be seen that there is some big
variance between runs, especially in the "big alloc" scenario. This is
probably being caused by nondeterministic behaviour in the kernel for
dynamic allocations. Still, it can be observed that there should be no
real difference between the "pluggable" and "fileline" allocators.

src/alloc.h

@@ -54,14 +54,14 @@
 
 #include "stdalloc.h"
 
-#define git__malloc(len)                      git__stdalloc__malloc(len)
-#define git__calloc(nelem, elsize)            git__stdalloc__calloc(nelem, elsize)
-#define git__strdup(str)                      git__stdalloc__strdup(str)
-#define git__strndup(str, n)                  git__stdalloc__strndup(str, n)
-#define git__substrdup(str, n)                git__stdalloc__substrdup(str, n)
-#define git__realloc(ptr, size)               git__stdalloc__realloc(ptr, size)
-#define git__reallocarray(ptr, nelem, elsize) git__stdalloc__reallocarray(ptr, nelem, elsize)
-#define git__mallocarray(nelem, elsize)       git__stdalloc__mallocarray(nelem, elsize)
+#define git__malloc(len)                      git__stdalloc__malloc(len, __FILE__, __LINE__)
+#define git__calloc(nelem, elsize)            git__stdalloc__calloc(nelem, elsize, __FILE__, __LINE__)
+#define git__strdup(str)                      git__stdalloc__strdup(str, __FILE__, __LINE__)
+#define git__strndup(str, n)                  git__stdalloc__strndup(str, n, __FILE__, __LINE__)
+#define git__substrdup(str, n)                git__stdalloc__substrdup(str, n, __FILE__, __LINE__)
+#define git__realloc(ptr, size)               git__stdalloc__realloc(ptr, size, __FILE__, __LINE__)
+#define git__reallocarray(ptr, nelem, elsize) git__stdalloc__reallocarray(ptr, nelem, elsize, __FILE__, __LINE__)
+#define git__mallocarray(nelem, elsize)       git__stdalloc__mallocarray(nelem, elsize, __FILE__, __LINE__)
 #define git__free                             git__stdalloc__free
 
 #endif /* !MSVC_CTRDBG */

src/stdalloc.c

@@ -7,28 +7,40 @@
 
 #include "stdalloc.h"
 
-void *git__stdalloc__malloc(size_t len)
+void *git__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;
 }
 
-void *git__stdalloc__calloc(size_t nelem, size_t elsize)
+void *git__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;
 }
 
-char *git__stdalloc__strdup(const char *str)
+char *git__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;
 }
 
-char *git__stdalloc__strndup(const char *str, size_t n)
+char *git__stdalloc__strndup(const char *str, size_t n, const char *file, int line)
 {
 	size_t length = 0, alloclength;
 	char *ptr;
@@ -36,7 +48,7 @@ char *git__stdalloc__strndup(const char *str, size_t n)
 	length = p_strnlen(str, n);
 
 	if (GIT_ADD_SIZET_OVERFLOW(&alloclength, length, 1) ||
-		!(ptr = git__stdalloc__malloc(alloclength)))
+		!(ptr = git__stdalloc__malloc(alloclength, file, line)))
 		return NULL;
 
 	if (length)
@@ -47,13 +59,13 @@ char *git__stdalloc__strndup(const char *str, size_t n)
 	return ptr;
 }
 
-char *git__stdalloc__substrdup(const char *start, size_t n)
+char *git__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 = git__stdalloc__malloc(alloclen)))
+		!(ptr = git__stdalloc__malloc(alloclen, file, line)))
 		return NULL;
 
 	memcpy(ptr, start, n);
@@ -61,23 +73,31 @@ char *git__stdalloc__substrdup(const char *start, size_t n)
 	return ptr;
 }
 
-void *git__stdalloc__realloc(void *ptr, size_t size)
+void *git__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;
 }
 
-void *git__stdalloc__reallocarray(void *ptr, size_t nelem, size_t elsize)
+void *git__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);
 }
 
-void *git__stdalloc__mallocarray(size_t nelem, size_t elsize)
+void *git__stdalloc__mallocarray(size_t nelem, size_t elsize, const char *file, int line)
 {
-	return git__stdalloc__reallocarray(NULL, nelem, elsize);
+	return git__stdalloc__reallocarray(NULL, nelem, elsize, file, line);
 }
 
 void git__stdalloc__free(void *ptr)

src/stdalloc.h

@@ -15,25 +15,25 @@
  * that set error code and error message
  * on allocation failure
  */
-void *git__stdalloc__malloc(size_t len);
-void *git__stdalloc__calloc(size_t nelem, size_t elsize);
-char *git__stdalloc__strdup(const char *str);
-char *git__stdalloc__strndup(const char *str, size_t n);
+void *git__stdalloc__malloc(size_t len, const char *file, int line);
+void *git__stdalloc__calloc(size_t nelem, size_t elsize, const char *file, int line);
+char *git__stdalloc__strdup(const char *str, const char *file, int line);
+char *git__stdalloc__strndup(const char *str, size_t n, const char *file, int line);
 /* NOTE: This doesn't do null or '\0' checking.  Watch those boundaries! */
-char *git__stdalloc__substrdup(const char *start, size_t n);
-void *git__stdalloc__realloc(void *ptr, size_t size);
+char *git__stdalloc__substrdup(const char *start, size_t n, const char *file, int line);
+void *git__stdalloc__realloc(void *ptr, size_t size, const char *file, int line);
 
 /**
  * Similar to `git__stdalloc__realloc`, except that it is suitable for reallocing an
  * array to a new number of elements of `nelem`, each of size `elsize`.
  * The total size calculation is checked for overflow.
  */
-void *git__stdalloc__reallocarray(void *ptr, size_t nelem, size_t elsize);
+void *git__stdalloc__reallocarray(void *ptr, size_t nelem, size_t elsize, const char *file, int line);
 
 /**
  * Similar to `git__stdalloc__calloc`, except that it does not zero memory.
  */
-void *git__stdalloc__mallocarray(size_t nelem, size_t elsize);
+void *git__stdalloc__mallocarray(size_t nelem, size_t elsize, const char *file, int line);
 
 void git__stdalloc__free(void *ptr);