Merge #20 Reserve a special section for memory leaks and automatic memory management.

modules/ROOT/pages/programming-languages/C.adoc

@@ -551,6 +551,38 @@ free the old pointer. Therefore, the idiom `ptr =
 realloc(ptr, size);` is wrong because the memory
 pointed to by `ptr` leaks in case of an error.
 
+==== Memory leaks
+After a memory area has been allocated with functions like `malloc`,
+`calloc`, etc. and it is no longer necessary, it must be freed in 
+order for the system to release the memory region and re-use it if 
+necessary. Failing to do so may lead to the application using more 
+memory than necessary and, in some cases, crashing due to no more 
+memory being available.
+
+If portability is not important in your program, an alternative way of
+automatic memory management is to leverage the `cleanup` attribute
+supported by the recent versions of GCC and Clang. If a local variable
+is declared with the attribute, the specified cleanup function will be
+called when the variable goes out of scope.
+
+[source,c]
+----
+static inline void freep(void *p) {
+        free(*(void**) p);
+}
+
+void somefunction(const char *param) {
+	if (strcmp(param, "do_something_complex") == 0) {
+		__attribute__((cleanup(freep))) char *ptr = NULL;
+
+		/* Allocate a temporary buffer */
+		ptr = malloc(size);
+
+		/* Do something on it, but do not need to manually call free() */
+	}
+}
+----
+
 [[sect-Defensive_Coding-C-Use-After-Free]]
 ==== Use-after-free errors
 
@@ -632,7 +664,7 @@ started as a GNU extension. For large objects exceeding the
 page size, there is no error checking, either.
 
 In both cases, negative or very large sizes can trigger a
-stack-pointer wraparound, and the stack pointer and end up
+stack-pointer wraparound, and the stack pointer ends up
 pointing into caller stack frames, which is fatal and can be
 exploitable.
 
@@ -644,30 +676,6 @@ Otherwise, call `malloc`. When exiting the
 function, check if `malloc` had been called,
 and free the buffer as needed.
 
-If portability is not important in your program, an alternative way of
-automatic memory management is to leverage the `cleanup` attribute
-supported by the recent versions of GCC and Clang. If a local variable
-is declared with the attribute, the specified cleanup function will be
-called when the variable goes out of scope.
-
-[source,c]
-----
-static inline void freep(void *p) {
-        free(*(void**) p);
-}
-
-void somefunction(const char *param) {
-	if (strcmp(param, "do_something_complex") == 0) {
-		__attribute__((cleanup(freep))) char *ptr = NULL;
-
-		/* Allocate a temporary buffer */
-		ptr = malloc(size);
-
-		/* Do something on it, but do not need to manually call free() */
-	}
-}
-----
-
 [[sect-Defensive_Coding-C-Allocators-Arrays]]
 === Array Allocation