S3519: Add notes for migration to LaYC

Adding very useful LaYC migration notes from Balazs.

rules/S3519/cfamily/rule.adoc

@@ -64,6 +64,76 @@ Secondary: * Index value for arrays
 == Comments And Links
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+Possible messages of the rule S3519:
+
+* alpha.security.ArrayBoundV2
+[source,cpp]
+----
+void access_exceeds(void) {
+  int id_sequence[3];
+  id_sequence[0] = 123;
+  id_sequence[1] = 234;
+  id_sequence[2] = 345;
+  id_sequence[3] = 456; // Noncompliant: accessing out of bounds.
+  // Out of bound memory access (access exceeds upper limit of memory block)
+}
+void access_precedes(int x) {
+  int buf[100];
+  int *p = buf;
+  --p;
+  p[0] = 1; // Out of bound memory access (accessed memory precedes memory block)
+}
+int getchar(void);
+void access_tainted(void) {
+  int m = getchar();
+  Buffer[m] = 1; // Out of bound memory access (index is tainted)
+}
+----
+
+* alpha.security.ReturnPtrRange
+[source,cpp]
+----
+int *test_idx_sym(int i) {
+  static int arr[10];
+  if (i != 40)
+    return arr;
+  return arr + i; // Returned pointer value points outside the original object
+}
+----
+
+* alpha.unix.cstring.OutOfBounds
+[source,cpp]
+----
+char* my_calloc(int n) {
+  char *p = malloc(n);
+  memset(p, 0, n + /*null terminator*/1); // OOB: off by one
+  // Memory set function overflows the destination buffer
+  return p;
+}
+void memcpy1(void) {
+  char src[] = {1, 2, 3, 4};
+  char dst[10];
+  memcpy(dst, src, 5); // Memory copy function accesses out-of-bound array element
+}
+----
+
+Typical bugs:
+* Off-by-one bugs
+
+Mitigations (extra mile):
+
+* asan
+* valgrind
+* Use "bounded" alternative functions, such as `strncpy`.
+* Compilation flags to harden the binary: FORTIFY_SOURCE, stack-canaries, ASLR
+* fuzzing
+
+Clarification question regarding inclusion forthis link in [https://discuss.sonarsource.com/t/layc-2023-languages-team-updates/14242/31?u=tomasz_kaminski[discuss].
+
+Possibly missing CWEs from rspec:
+* https://cwe.mitre.org/data/definitions/787.html
+* https://cwe.mitre.org/data/definitions/193.html
+
 === is related to: S5782
 
 endif::env-github,rspecator-view[]