diff --git a/changes/ticket31532 b/changes/ticket31532
new file mode 100644
index 0000000000..95bcbc517c
--- /dev/null
+++ b/changes/ticket31532
@@ -0,0 +1,4 @@
+  o Code simplification and refactoring:
+    - Use the ptrdiff_t type consistently for expressing variable offsets and
+      pointer differences.  Previously we incorrectly (but harmlessly) used
+      int and sometimes off_t for these cases.  Closes ticket 31532.
diff --git a/src/app/config/confparse.h b/src/app/config/confparse.h
index b788e2cd1b..fc07996aab 100644
--- a/src/app/config/confparse.h
+++ b/src/app/config/confparse.h
@@ -72,7 +72,7 @@ typedef struct config_format_t {
   const struct_member_t *extra;
   /** The position of a config_suite_t pointer within the toplevel object,
    * or -1 if there is no such pointer. */
-  int config_suite_offset;
+  ptrdiff_t config_suite_offset;
 } config_format_t;
 
 /**
diff --git a/src/feature/rend/rendclient.c b/src/feature/rend/rendclient.c
index 5bdd4d453e..2540066dfc 100644
--- a/src/feature/rend/rendclient.c
+++ b/src/feature/rend/rendclient.c
@@ -119,7 +119,7 @@ rend_client_send_introduction(origin_circuit_t *introcirc,
   char tmp[RELAY_PAYLOAD_SIZE];
   rend_cache_entry_t *entry = NULL;
   crypt_path_t *cpath;
-  off_t dh_offset;
+  ptrdiff_t dh_offset;
   crypto_pk_t *intro_key = NULL;
   int status = 0;
   const char *onion_address;
diff --git a/src/lib/buf/buffers.c b/src/lib/buf/buffers.c
index 88a25b8470..4d026bd37d 100644
--- a/src/lib/buf/buffers.c
+++ b/src/lib/buf/buffers.c
@@ -158,7 +158,7 @@ chunk_new_with_alloc_size(size_t alloc)
 static inline chunk_t *
 chunk_grow(chunk_t *chunk, size_t sz)
 {
-  off_t offset;
+  ptrdiff_t offset;
   const size_t memlen_orig = chunk->memlen;
   const size_t orig_alloc = CHUNK_ALLOC_SIZE(memlen_orig);
   const size_t new_alloc = CHUNK_ALLOC_SIZE(sz);
@@ -440,7 +440,7 @@ chunk_copy(const chunk_t *in_chunk)
 #endif
   newch->next = NULL;
   if (in_chunk->data) {
-    off_t offset = in_chunk->data - in_chunk->mem;
+    ptrdiff_t offset = in_chunk->data - in_chunk->mem;
     newch->data = newch->mem + offset;
   }
   return newch;
@@ -710,7 +710,8 @@ buf_move_all(buf_t *buf_out, buf_t *buf_in)
 /** Internal structure: represents a position in a buffer. */
 typedef struct buf_pos_t {
   const chunk_t *chunk; /**< Which chunk are we pointing to? */
-  int pos;/**< Which character inside the chunk's data are we pointing to? */
+  ptrdiff_t pos;/**< Which character inside the chunk's data are we pointing
+                 * to? */
   size_t chunk_pos; /**< Total length of all previous chunks. */
 } buf_pos_t;
 
@@ -726,15 +727,15 @@ buf_pos_init(const buf_t *buf, buf_pos_t *out)
 /** Advance <b>out</b> to the first appearance of <b>ch</b> at the current
  * position of <b>out</b>, or later.  Return -1 if no instances are found;
  * otherwise returns the absolute position of the character. */
-static off_t
+static ptrdiff_t
 buf_find_pos_of_char(char ch, buf_pos_t *out)
 {
   const chunk_t *chunk;
-  int pos;
+  ptrdiff_t pos;
   tor_assert(out);
   if (out->chunk) {
     if (out->chunk->datalen) {
-      tor_assert(out->pos < (off_t)out->chunk->datalen);
+      tor_assert(out->pos < (ptrdiff_t)out->chunk->datalen);
     } else {
       tor_assert(out->pos == 0);
     }
@@ -762,7 +763,7 @@ buf_pos_inc(buf_pos_t *pos)
 {
   tor_assert(pos->pos < INT_MAX - 1);
   ++pos->pos;
-  if (pos->pos == (off_t)pos->chunk->datalen) {
+  if (pos->pos == (ptrdiff_t)pos->chunk->datalen) {
     if (!pos->chunk->next)
       return -1;
     pos->chunk_pos += pos->chunk->datalen;
@@ -836,11 +837,11 @@ buf_peek_startswith(const buf_t *buf, const char *cmd)
 
 /** Return the index within <b>buf</b> at which <b>ch</b> first appears,
  * or -1 if <b>ch</b> does not appear on buf. */
-static off_t
+static ptrdiff_t
 buf_find_offset_of_char(buf_t *buf, char ch)
 {
   chunk_t *chunk;
-  off_t offset = 0;
+  ptrdiff_t offset = 0;
   tor_assert(buf->datalen < INT_MAX);
   for (chunk = buf->head; chunk; chunk = chunk->next) {
     char *cp = memchr(chunk->data, ch, chunk->datalen);
@@ -863,7 +864,7 @@ int
 buf_get_line(buf_t *buf, char *data_out, size_t *data_len)
 {
   size_t sz;
-  off_t offset;
+  ptrdiff_t offset;
 
   if (!buf->head)
     return 0;
diff --git a/src/lib/cc/compat_compiler.h b/src/lib/cc/compat_compiler.h
index a8d1593214..92301449e8 100644
--- a/src/lib/cc/compat_compiler.h
+++ b/src/lib/cc/compat_compiler.h
@@ -195,7 +195,7 @@
  * structure <b>st</b>.  Example:
  * <pre>
  *   struct a { int foo; int bar; } x;
- *   off_t bar_offset = offsetof(struct a, bar);
+ *   ptrdiff_t bar_offset = offsetof(struct a, bar);
  *   int *bar_p = STRUCT_VAR_P(&x, bar_offset);
  *   *bar_p = 3;
  * </pre>
diff --git a/src/lib/conf/conftypes.h b/src/lib/conf/conftypes.h
index fabad97d0c..abfb53b21b 100644
--- a/src/lib/conf/conftypes.h
+++ b/src/lib/conf/conftypes.h
@@ -33,6 +33,8 @@
 #include "lib/conf/conftesting.h"
 #endif
 
+#include <stddef.h>
+
 /** Enumeration of types which option values can take */
 typedef enum config_type_t {
   CONFIG_TYPE_STRING = 0,   /**< An arbitrary string. */
@@ -89,7 +91,7 @@ typedef struct struct_member_t {
    * Offset of this field within the structure.  Compute this with
    * offsetof(structure, fieldname).
    **/
-  int offset;
+  ptrdiff_t offset;
 } struct_member_t;
 
 /**
@@ -102,7 +104,7 @@ typedef struct struct_member_t {
 typedef struct struct_magic_decl_t {
   const char *typename;
   uint32_t magic_val;
-  int magic_offset;
+  ptrdiff_t magic_offset;
 } struct_magic_decl_t;
 
 /**
diff --git a/src/lib/container/smartlist.c b/src/lib/container/smartlist.c
index 3ab2797d68..2b71c11287 100644
--- a/src/lib/container/smartlist.c
+++ b/src/lib/container/smartlist.c
@@ -678,7 +678,7 @@ smartlist_sort_pointers(smartlist_t *sl)
 static inline void
 smartlist_heapify(smartlist_t *sl,
                   int (*compare)(const void *a, const void *b),
-                  int idx_field_offset,
+                  ptrdiff_t idx_field_offset,
                   int idx)
 {
   while (1) {
@@ -725,7 +725,7 @@ smartlist_heapify(smartlist_t *sl,
 void
 smartlist_pqueue_add(smartlist_t *sl,
                      int (*compare)(const void *a, const void *b),
-                     int idx_field_offset,
+                     ptrdiff_t idx_field_offset,
                      void *item)
 {
   int idx;
@@ -754,7 +754,7 @@ smartlist_pqueue_add(smartlist_t *sl,
 void *
 smartlist_pqueue_pop(smartlist_t *sl,
                      int (*compare)(const void *a, const void *b),
-                     int idx_field_offset)
+                     ptrdiff_t idx_field_offset)
 {
   void *top;
   tor_assert(sl->num_used);
@@ -778,7 +778,7 @@ smartlist_pqueue_pop(smartlist_t *sl,
 void
 smartlist_pqueue_remove(smartlist_t *sl,
                         int (*compare)(const void *a, const void *b),
-                        int idx_field_offset,
+                        ptrdiff_t idx_field_offset,
                         void *item)
 {
   int idx = IDX_OF_ITEM(item);
@@ -802,7 +802,7 @@ smartlist_pqueue_remove(smartlist_t *sl,
 void
 smartlist_pqueue_assert_ok(smartlist_t *sl,
                            int (*compare)(const void *a, const void *b),
-                           int idx_field_offset)
+                           ptrdiff_t idx_field_offset)
 {
   int i;
   for (i = sl->num_used - 1; i >= 0; --i) {
diff --git a/src/lib/container/smartlist.h b/src/lib/container/smartlist.h
index 81b0151433..25638e4b22 100644
--- a/src/lib/container/smartlist.h
+++ b/src/lib/container/smartlist.h
@@ -13,6 +13,7 @@
  **/
 
 #include <stdarg.h>
+#include <stddef.h>
 
 #include "lib/smartlist_core/smartlist_core.h"
 #include "lib/smartlist_core/smartlist_foreach.h"
@@ -72,18 +73,18 @@ int smartlist_bsearch_idx(const smartlist_t *sl, const void *key,
 
 void smartlist_pqueue_add(smartlist_t *sl,
                           int (*compare)(const void *a, const void *b),
-                          int idx_field_offset,
+                          ptrdiff_t idx_field_offset,
                           void *item);
 void *smartlist_pqueue_pop(smartlist_t *sl,
                            int (*compare)(const void *a, const void *b),
-                           int idx_field_offset);
+                           ptrdiff_t idx_field_offset);
 void smartlist_pqueue_remove(smartlist_t *sl,
                              int (*compare)(const void *a, const void *b),
-                             int idx_field_offset,
+                             ptrdiff_t idx_field_offset,
                              void *item);
 void smartlist_pqueue_assert_ok(smartlist_t *sl,
                                 int (*compare)(const void *a, const void *b),
-                                int idx_field_offset);
+                                ptrdiff_t idx_field_offset);
 
 char *smartlist_join_strings(smartlist_t *sl, const char *join, int terminate,
                              size_t *len_out) ATTR_MALLOC;