Fix adjust to be ptrdiff_t

As per: #127523 (comment)

Author: vinay-deshmukh

libc/src/string/memory_utils/utils.h

@@ -17,6 +17,7 @@
 #include "src/__support/macros/config.h"     // LIBC_NAMESPACE_DECL
 #include "src/__support/macros/properties/architectures.h"
 
+#include <cstddef>
 #include <stddef.h> // size_t
 #include <stdint.h> // intptr_t / uintptr_t / INT32_MAX / INT32_MIN
 
@@ -293,11 +294,11 @@ LIBC_INLINE void store64_aligned(uint64_t value, Ptr dst, size_t offset) {
 // Advances the pointers p1 and p2 by offset bytes and decrease count by the
 // same amount.
 template <typename T1, typename T2>
-LIBC_INLINE void adjust(uintptr_t offset, T1 *__restrict &p1,
+LIBC_INLINE void adjust(ptrdiff_t offset, T1 *__restrict &p1,
                         T2 *__restrict &p2, size_t &count) {
   p1 += offset;
   p2 += offset;
-  count -= offset;
+  count -= static_cast<size_t>(offset);
 }
 
 // Advances p1 and p2 so p1 gets aligned to the next SIZE bytes boundary
@@ -306,7 +307,7 @@ LIBC_INLINE void adjust(uintptr_t offset, T1 *__restrict &p1,
 template <size_t SIZE, typename T1, typename T2>
 void align_p1_to_next_boundary(T1 *__restrict &p1, T2 *__restrict &p2,
                                size_t &count) {
-  adjust(distance_to_next_aligned<SIZE>(p1), p1, p2, count);
+  adjust(static_cast<ptrdiff_t>(distance_to_next_aligned<SIZE>(p1)), p1, p2, count);
   p1 = assume_aligned<SIZE>(p1);
 }
 

libc/test/src/string/memory_utils/utils_test.cpp

@@ -51,7 +51,7 @@ TEST(LlvmLibcUtilsTest, Adjust2) {
     auto *p1 = &a;
     auto *p2 = &b;
     size_t size = base_size;
-    adjust(I, p1, p2, size);
+    adjust(static_cast<ptrdiff_t>(I), p1, p2, size);
     EXPECT_EQ(intptr_t(p1), intptr_t(&a + I));
     EXPECT_EQ(intptr_t(p2), intptr_t(&b + I));
     EXPECT_EQ(size, base_size - I);