[analyzer] CStringChecker: Fix crash in CheckOverlap when arguments are not pointers (#160511)

https://github.com/llvm/llvm-project/blob/main/clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp#L675-L678
mistakenly assumes that target expressions are of pointer type.
`CheckOverlap` has multiple call sites, most of which do not verify this
assumption. Therefore, the simplest solution is to verify it just before
that point.

Author: guillem-bartrina-sonarsource

clang/lib/StaticAnalyzer/Checkers/CStringChecker.cpp

@@ -672,6 +672,10 @@ ProgramStateRef CStringChecker::CheckOverlap(CheckerContext &C,
 
   ProgramStateRef stateTrue, stateFalse;
 
+  if (!First.Expression->getType()->isAnyPointerType() ||
+      !Second.Expression->getType()->isAnyPointerType())
+    return state;
+
   // Assume different address spaces cannot overlap.
   if (First.Expression->getType()->getPointeeType().getAddressSpace() !=
       Second.Expression->getType()->getPointeeType().getAddressSpace())

clang/test/Analysis/buffer-overlap-decls.c

@@ -0,0 +1,23 @@
+// RUN: %clang_analyze_cc1 -verify %s -Wno-incompatible-library-redeclaration \
+// RUN:   -analyzer-checker=alpha.unix.cstring.BufferOverlap
+// expected-no-diagnostics
+
+typedef typeof(sizeof(int)) size_t;
+
+void memcpy(int dst, int src, size_t size);
+
+void test_memcpy_proxy() {
+  memcpy(42, 42, 42); // no-crash
+}
+
+void strcpy(int dst, char *src);
+
+void test_strcpy_proxy() {
+  strcpy(42, (char *)42); // no-crash
+}
+
+void strxfrm(int dst, char *src, size_t size);
+
+void test_strxfrm_proxy() {
+  strxfrm(42, (char *)42, 42); // no-crash
+}

clang/test/Analysis/buffer-overlap.c

@@ -96,3 +96,10 @@ void test_snprintf6() {
   char b[4] = {0};
   snprintf(a, sizeof(a), "%s", b); // no-warning
 }
+
+void* memcpy(void* dest, const void* src, size_t count);
+
+void test_memcpy_esoteric() {
+label:
+  memcpy((char *)&&label, (const char *)memcpy, 1);
+}