build: enable -Wshadow

Note about shada.c:
- shada_read_next_item_start was intentionally shadowing `unpacked` and
  `i` because many of the macros (e.g. ADDITIONAL_KEY) implicitly
  depended on those variable names.
- Macros were changed to parameterize `unpacked` (but not `i`). Macros
  like CLEAR_GA_AND_ERROR_OUT do control-flow (goto), so any other
  approach is messy.

18 files changed, 178 insertions, 166 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 32cbe8472e..7e73443ec2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -174,7 +174,7 @@ endif()
 
 # Enable -Wconversion.
 if(NOT MSVC)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wconversion")
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wshadow -Wconversion")
 endif()
 
 # gcc 4.0+ sets _FORTIFY_SOURCE=2 automatically.  This currently
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index f1cce716e0..460e454048 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -2380,7 +2380,7 @@ static void set_var_lval(lval_T *lp, char_u *endp, typval_T *rettv,
     int ll_n1 = lp->ll_n1;
 
     // Check whether any of the list items is locked
-    for (listitem_T *ri = tv_list_first(rettv->vval.v_list);
+    for (ri = tv_list_first(rettv->vval.v_list);
          ri != NULL && ll_li != NULL; ) {
       if (tv_check_lock(TV_LIST_ITEM_TV(ll_li)->v_lock,
                         (const char *)lp->ll_name,
@@ -2476,9 +2476,9 @@ notify:
         assert(lp->ll_newkey != NULL);
         tv_dict_watcher_notify(dict, (char *)lp->ll_newkey, lp->ll_tv, NULL);
       } else {
-        dictitem_T *di = lp->ll_di;
-        assert(di->di_key != NULL);
-        tv_dict_watcher_notify(dict, (char *)di->di_key, lp->ll_tv, &oldtv);
+        dictitem_T *di_ = lp->ll_di;
+        assert(di_->di_key != NULL);
+        tv_dict_watcher_notify(dict, (char *)di_->di_key, lp->ll_tv, &oldtv);
         tv_clear(&oldtv);
       }
     }
@@ -5234,8 +5234,6 @@ bool garbage_collect(bool testing)
 /// @return true, if something was freed.
 static int free_unref_items(int copyID)
 {
-  dict_T *dd, *dd_next;
-  list_T *ll, *ll_next;
   bool did_free = false;
 
   // Let all "free" functions know that we are here. This means no
@@ -5273,14 +5271,16 @@ static int free_unref_items(int copyID)
   }
 
   // PASS 2: free the items themselves.
-  for (dd = gc_first_dict; dd != NULL; dd = dd_next) {
+  dict_T *dd_next;
+  for (dict_T *dd = gc_first_dict; dd != NULL; dd = dd_next) {
     dd_next = dd->dv_used_next;
     if ((dd->dv_copyID & COPYID_MASK) != (copyID & COPYID_MASK)) {
       tv_dict_free_dict(dd);
     }
   }
 
-  for (ll = gc_first_list; ll != NULL; ll = ll_next) {
+  list_T *ll_next;
+  for (list_T *ll = gc_first_list; ll != NULL; ll = ll_next) {
     ll_next = ll->lv_used_next;
     if ((ll->lv_copyID & COPYID_MASK) != (copyID & COPYID_MASK)
         && !tv_list_has_watchers(ll)) {
@@ -11508,23 +11508,23 @@ static void dict_list(typval_T *const tv, typval_T *const rettv,
   tv_list_alloc_ret(rettv, tv_dict_len(tv->vval.v_dict));
 
   TV_DICT_ITER(tv->vval.v_dict, di, {
-    typval_T tv = { .v_lock = VAR_UNLOCKED };
+    typval_T tv_item = { .v_lock = VAR_UNLOCKED };
 
     switch (what) {
       case kDictListKeys: {
-        tv.v_type = VAR_STRING;
-        tv.vval.v_string = vim_strsave(di->di_key);
+        tv_item.v_type = VAR_STRING;
+        tv_item.vval.v_string = vim_strsave(di->di_key);
         break;
       }
       case kDictListValues: {
-        tv_copy(&di->di_tv, &tv);
+        tv_copy(&di->di_tv, &tv_item);
         break;
       }
       case kDictListItems: {
         // items()
         list_T *const sub_l = tv_list_alloc(2);
-        tv.v_type = VAR_LIST;
-        tv.vval.v_list = sub_l;
+        tv_item.v_type = VAR_LIST;
+        tv_item.vval.v_list = sub_l;
         tv_list_ref(sub_l);
 
         tv_list_append_owned_tv(sub_l, (typval_T) {
@@ -11539,7 +11539,7 @@ static void dict_list(typval_T *const tv, typval_T *const rettv,
       }
     }
 
-    tv_list_append_owned_tv(rettv->vval.v_list, tv);
+    tv_list_append_owned_tv(rettv->vval.v_list, tv_item);
   });
 }
 
@@ -14785,12 +14785,12 @@ static void f_setmatches(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   list_T *const l = argvars[0].vval.v_list;
   // To some extent make sure that we are dealing with a list from
   // "getmatches()".
-  int i = 0;
+  int li_idx = 0;
   TV_LIST_ITER_CONST(l, li, {
     if (TV_LIST_ITEM_TV(li)->v_type != VAR_DICT
         || (d = TV_LIST_ITEM_TV(li)->vval.v_dict) == NULL) {
       emsgf(_("E474: List item %d is either not a dictionary "
-              "or an empty one"), i);
+              "or an empty one"), li_idx);
       return;
     }
     if (!(tv_dict_find(d, S_LEN("group")) != NULL
@@ -14798,10 +14798,11 @@ static void f_setmatches(typval_T *argvars, typval_T *rettv, FunPtr fptr)
               || tv_dict_find(d, S_LEN("pos1")) != NULL)
           && tv_dict_find(d, S_LEN("priority")) != NULL
           && tv_dict_find(d, S_LEN("id")) != NULL)) {
-      emsgf(_("E474: List item %d is missing one of the required keys"), i);
+      emsgf(_("E474: List item %d is missing one of the required keys"),
+            li_idx);
       return;
     }
-    i++;
+    li_idx++;
   });
 
   clear_matches(curwin);
diff --git a/src/nvim/eval/encode.c b/src/nvim/eval/encode.c
index e9ab6cd3e2..64658b52d9 100644
--- a/src/nvim/eval/encode.c
+++ b/src/nvim/eval/encode.c
@@ -302,11 +302,11 @@ int encode_read_from_list(ListReaderState *const state, char *const buf,
         const size_t len_ = (len); \
         ga_grow(gap, (int) (2 + len_ + memcnt(buf_, '\'', len_))); \
         ga_append(gap, '\''); \
-        for (size_t i = 0; i < len_; i++) { \
-          if (buf_[i] == '\'') { \
+        for (size_t i_ = 0; i_ < len_; i_++) { \
+          if (buf_[i_] == '\'') { \
             ga_append(gap, '\''); \
           } \
-          ga_append(gap, buf_[i]); \
+          ga_append(gap, buf_[i_]); \
         } \
         ga_append(gap, '\''); \
       } \
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index 51d20c746a..6b0d8801fd 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -2130,9 +2130,9 @@ void ex_listdo(exarg_T *eap)
         // Remember the number of the next listed buffer, in case
         // ":bwipe" is used or autocommands do something strange.
         next_fnum = -1;
-        for (buf_T *buf = curbuf->b_next; buf != NULL; buf = buf->b_next) {
-          if (buf->b_p_bl) {
-            next_fnum = buf->b_fnum;
+        for (buf_T *bp = curbuf->b_next; bp != NULL; bp = bp->b_next) {
+          if (bp->b_p_bl) {
+            next_fnum = bp->b_fnum;
             break;
           }
         }
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index fe12a69801..c631057e81 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -5997,9 +5997,8 @@ void do_autocmd(char_u *arg_in, int forceit)
   char_u      *pat;
   char_u      *envpat = NULL;
   char_u      *cmd;
-  event_T event;
-  int need_free = FALSE;
-  int nested = FALSE;
+  int need_free = false;
+  int nested = false;
   int group;
 
   if (*arg == '|') {
@@ -6082,7 +6081,7 @@ void do_autocmd(char_u *arg_in, int forceit)
   last_event = (event_T)-1;             // for listing the event name
   last_group = AUGROUP_ERROR;           // for listing the group name
   if (*arg == '*' || *arg == NUL || *arg == '|') {
-    for (event = (event_T)0; (int)event < (int)NUM_EVENTS;
+    for (event_T event = (event_T)0; (int)event < (int)NUM_EVENTS;
          event = (event_T)((int)event + 1)) {
       if (do_autocmd_event(event, pat, nested, cmd, forceit, group) == FAIL) {
         break;
diff --git a/src/nvim/main.c b/src/nvim/main.c
index 8a40577e8f..17f3a894d4 100644
--- a/src/nvim/main.c
+++ b/src/nvim/main.c
@@ -781,7 +781,6 @@ static void command_line_scan(mparm_T *parmp)
   bool had_minmin = false;              // found "--" argument
   int want_argument;                    // option argument with argument
   int c;
-  char_u *p = NULL;
   long n;
 
   argc--;
@@ -1227,7 +1226,7 @@ scripterror:
 
       // Add the file to the global argument list.
       ga_grow(&global_alist.al_ga, 1);
-      p = vim_strsave((char_u *)argv[0]);
+      char_u *p = vim_strsave((char_u *)argv[0]);
 
       if (parmp->diff_mode && os_isdir(p) && GARGCOUNT > 0
           && !os_isdir(alist_name(&GARGLIST[0]))) {
diff --git a/src/nvim/misc1.c b/src/nvim/misc1.c
index 5f76458275..a66ded13f1 100644
--- a/src/nvim/misc1.c
+++ b/src/nvim/misc1.c
@@ -203,7 +203,7 @@ open_line (
       char_u  *ptr;
       char_u last_char;
 
-      pos_T old_cursor = curwin->w_cursor;
+      old_cursor = curwin->w_cursor;
       ptr = saved_line;
       if (flags & OPENLINE_DO_COM)
         lead_len = get_leader_len(ptr, NULL, FALSE, TRUE);
diff --git a/src/nvim/msgpack_rpc/channel.c b/src/nvim/msgpack_rpc/channel.c
index 46a9e95b91..76fbe407c2 100644
--- a/src/nvim/msgpack_rpc/channel.c
+++ b/src/nvim/msgpack_rpc/channel.c
@@ -495,8 +495,8 @@ static void broadcast_event(const char *name, Array args)
                                       kv_size(subscribed));
 
   for (size_t i = 0; i < kv_size(subscribed); i++) {
-    Channel *channel = kv_A(subscribed, i);
-    channel_write(channel, buffer);
+    Channel *c = kv_A(subscribed, i);
+    channel_write(c, buffer);
   }
 
 end:
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index 5a6e56299d..e9cb480647 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -2670,7 +2670,6 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
   colnr_T vcol;
   int delcount;
   int incr = 0;
-  long j;
   struct block_def bd;
   char_u      **y_array = NULL;
   long nr_lines = 0;
@@ -2840,16 +2839,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
   }
 
   if (curbuf->terminal) {
-    for (int i = 0; i < count; i++) {  // -V756
-      // feed the lines to the terminal
-      for (size_t j = 0; j < y_size; j++) {
-        if (j) {
-          // terminate the previous line
-          terminal_send(curbuf->terminal, "\n", 1);
-        }
-        terminal_send(curbuf->terminal, (char *)y_array[j], STRLEN(y_array[j]));
-      }
-    }
+    terminal_paste(count, y_array, y_size);
     return;
   }
 
@@ -3035,12 +3025,14 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
 
       yanklen = (int)STRLEN(y_array[i]);
 
-      /* calculate number of spaces required to fill right side of block*/
+      // calculate number of spaces required to fill right side of block
       spaces = y_width + 1;
-      for (j = 0; j < yanklen; j++)
+      for (long j = 0; j < yanklen; j++) {
         spaces -= lbr_chartabsize(NULL, &y_array[i][j], 0);
-      if (spaces < 0)
+      }
+      if (spaces < 0) {
         spaces = 0;
+      }
 
       // insert the new text
       totlen = (size_t)(count * (yanklen + spaces)
@@ -3050,21 +3042,21 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
       ptr = newp;
       memmove(ptr, oldp, (size_t)bd.textcol);
       ptr += bd.textcol;
-      /* may insert some spaces before the new text */
+      // may insert some spaces before the new text
       memset(ptr, ' ', (size_t)bd.startspaces);
       ptr += bd.startspaces;
-      /* insert the new text */
-      for (j = 0; j < count; ++j) {
+      // insert the new text
+      for (long j = 0; j < count; j++) {
         memmove(ptr, y_array[i], (size_t)yanklen);
         ptr += yanklen;
 
-        /* insert block's trailing spaces only if there's text behind */
+        // insert block's trailing spaces only if there's text behind
         if ((j < count - 1 || !shortline) && spaces) {
           memset(ptr, ' ', (size_t)spaces);
           ptr += spaces;
         }
       }
-      /* may insert some spaces after the new text */
+      // may insert some spaces after the new text
       memset(ptr, ' ', (size_t)bd.endspaces);
       ptr += bd.endspaces;
       // move the text after the cursor to the end of the line.
@@ -5697,12 +5689,12 @@ static bool get_clipboard(int name, yankreg_T **target, bool quiet)
   // Timestamp is not saved for clipboard registers because clipboard registers
   // are not saved in the ShaDa file.
 
-  int i = 0;
+  size_t tv_idx = 0;
   TV_LIST_ITER_CONST(lines, li, {
     if (TV_LIST_ITEM_TV(li)->v_type != VAR_STRING) {
       goto err;
     }
-    reg->y_array[i++] = (char_u *)xstrdupnul(
+    reg->y_array[tv_idx++] = (char_u *)xstrdupnul(
         (const char *)TV_LIST_ITEM_TV(li)->vval.v_string);
   });
 
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index d9e307bb71..4eeddf1d5a 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -925,11 +925,11 @@ restofline:
           return QF_FAIL;
         }
         if (*fields->errmsg) {
-          size_t len = STRLEN(qfprev->qf_text);
+          size_t textlen = STRLEN(qfprev->qf_text);
           qfprev->qf_text = xrealloc(qfprev->qf_text,
-                                     len + STRLEN(fields->errmsg) + 2);
-          qfprev->qf_text[len] = '\n';
-          STRCPY(qfprev->qf_text + len + 1, fields->errmsg);
+                                     textlen + STRLEN(fields->errmsg) + 2);
+          qfprev->qf_text[textlen] = '\n';
+          STRCPY(qfprev->qf_text + textlen + 1, fields->errmsg);
         }
         if (qfprev->qf_nr == -1) {
           qfprev->qf_nr = fields->enr;
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index c05ee5117a..1e07bbb5e3 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -4006,23 +4006,23 @@ win_line (
             draw_color_col = advance_color_col(VCOL_HLC, &color_cols);
           }
 
-          int attr = base_attr;
+          int col_attr = base_attr;
 
           if (wp->w_p_cuc && VCOL_HLC == (long)wp->w_virtcol) {
-            attr = cuc_attr;
+            col_attr = cuc_attr;
           } else if (draw_color_col && VCOL_HLC == *color_cols) {
-            attr = mc_attr;
+            col_attr = mc_attr;
           }
 
           if (do_virttext) {
-            attr = hl_combine_attr(attr, virt_attr);
+            col_attr = hl_combine_attr(col_attr, virt_attr);
           }
 
-          attr = hl_combine_attr(attr, line_attr);
+          col_attr = hl_combine_attr(col_attr, line_attr);
 
-          linebuf_attr[off] = attr;
+          linebuf_attr[off] = col_attr;
           if (cells == 2) {
-            linebuf_attr[off+1] = attr;
+            linebuf_attr[off+1] = col_attr;
           }
           off += cells * col_stride;
 
@@ -5200,9 +5200,9 @@ win_redr_custom (
   curattr = attr;
   p = buf;
   for (n = 0; hltab[n].start != NULL; n++) {
-    int len = (int)(hltab[n].start - p);
-    grid_puts_len(&default_grid, p, len, row, col, curattr);
-    col += vim_strnsize(p, len);
+    int textlen = (int)(hltab[n].start - p);
+    grid_puts_len(&default_grid, p, textlen, row, col, curattr);
+    col += vim_strnsize(p, textlen);
     p = hltab[n].start;
 
     if (hltab[n].userhl == 0)
diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 11da7195bf..72330453e7 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -3475,53 +3475,55 @@ static ShaDaReadResult msgpack_read_uint64(ShaDaReadDef *const sd_reader,
     } \
     tgt = proc(obj.via.attr); \
   } while (0)
-#define CHECK_KEY_IS_STR(entry_name) \
-  if (unpacked.data.via.map.ptr[i].key.type != MSGPACK_OBJECT_STR) { \
+#define CHECK_KEY_IS_STR(un, entry_name) \
+  if (un.data.via.map.ptr[i].key.type != MSGPACK_OBJECT_STR) { \
     emsgf(_(READERR(entry_name, "has key which is not a string")), \
           initial_fpos); \
     CLEAR_GA_AND_ERROR_OUT(ad_ga); \
-  } else if (unpacked.data.via.map.ptr[i].key.via.str.size == 0) { \
+  } else if (un.data.via.map.ptr[i].key.via.str.size == 0) { \
     emsgf(_(READERR(entry_name, "has empty key")), initial_fpos); \
     CLEAR_GA_AND_ERROR_OUT(ad_ga); \
   }
-#define CHECKED_KEY(entry_name, name, error_desc, tgt, condition, attr, proc) \
+#define CHECKED_KEY(un, entry_name, name, error_desc, tgt, condition, attr, \
+                    proc) \
   else if (CHECK_KEY( /* NOLINT(readability/braces) */ \
-      unpacked.data.via.map.ptr[i].key, name)) { \
+      un.data.via.map.ptr[i].key, name)) { \
     CHECKED_ENTRY( \
         condition, "has " name " key value " error_desc, \
-        entry_name, unpacked.data.via.map.ptr[i].val, \
+        entry_name, un.data.via.map.ptr[i].val, \
         tgt, attr, proc); \
   }
-#define TYPED_KEY(entry_name, name, type_name, tgt, objtype, attr, proc) \
+#define TYPED_KEY(un, entry_name, name, type_name, tgt, objtype, attr, proc) \
   CHECKED_KEY( \
-      entry_name, name, "which is not " type_name, tgt, \
-      unpacked.data.via.map.ptr[i].val.type == MSGPACK_OBJECT_##objtype, \
+      un, entry_name, name, "which is not " type_name, tgt, \
+      un.data.via.map.ptr[i].val.type == MSGPACK_OBJECT_##objtype, \
       attr, proc)
-#define BOOLEAN_KEY(entry_name, name, tgt) \
-  TYPED_KEY(entry_name, name, "a boolean", tgt, BOOLEAN, boolean, ID)
-#define STRING_KEY(entry_name, name, tgt) \
-  TYPED_KEY(entry_name, name, "a binary", tgt, BIN, bin, BINDUP)
-#define CONVERTED_STRING_KEY(entry_name, name, tgt) \
-  TYPED_KEY(entry_name, name, "a binary", tgt, BIN, bin, BIN_CONVERTED)
-#define INT_KEY(entry_name, name, tgt, proc) \
+#define BOOLEAN_KEY(un, entry_name, name, tgt) \
+  TYPED_KEY(un, entry_name, name, "a boolean", tgt, BOOLEAN, boolean, ID)
+#define STRING_KEY(un, entry_name, name, tgt) \
+  TYPED_KEY(un, entry_name, name, "a binary", tgt, BIN, bin, BINDUP)
+#define CONVERTED_STRING_KEY(un, entry_name, name, tgt) \
+  TYPED_KEY(un, entry_name, name, "a binary", tgt, BIN, bin, \
+            BIN_CONVERTED)
+#define INT_KEY(un, entry_name, name, tgt, proc) \
   CHECKED_KEY( \
-      entry_name, name, "which is not an integer", tgt, \
-      ((unpacked.data.via.map.ptr[i].val.type \
+      un, entry_name, name, "which is not an integer", tgt, \
+      ((un.data.via.map.ptr[i].val.type \
         == MSGPACK_OBJECT_POSITIVE_INTEGER) \
-       || (unpacked.data.via.map.ptr[i].val.type \
+       || (un.data.via.map.ptr[i].val.type \
            == MSGPACK_OBJECT_NEGATIVE_INTEGER)), \
       i64, proc)
-#define INTEGER_KEY(entry_name, name, tgt) \
-  INT_KEY(entry_name, name, tgt, TOINT)
-#define LONG_KEY(entry_name, name, tgt) \
-  INT_KEY(entry_name, name, tgt, TOLONG)
-#define ADDITIONAL_KEY \
+#define INTEGER_KEY(un, entry_name, name, tgt) \
+  INT_KEY(un, entry_name, name, tgt, TOINT)
+#define LONG_KEY(un, entry_name, name, tgt) \
+  INT_KEY(un, entry_name, name, tgt, TOLONG)
+#define ADDITIONAL_KEY(un) \
   else { /* NOLINT(readability/braces) */ \
     ga_grow(&ad_ga, 1); \
-    memcpy(((char *)ad_ga.ga_data) + ((size_t) ad_ga.ga_len \
-                                      * sizeof(*unpacked.data.via.map.ptr)), \
-           unpacked.data.via.map.ptr + i, \
-           sizeof(*unpacked.data.via.map.ptr)); \
+    memcpy(((char *)ad_ga.ga_data) + ((size_t)ad_ga.ga_len \
+                                      * sizeof(*un.data.via.map.ptr)), \
+           un.data.via.map.ptr + i, \
+           sizeof(*un.data.via.map.ptr)); \
     ad_ga.ga_len++; \
   }
 #define CONVERTED(str, len) (xmemdupz((str), (len)))
@@ -3726,28 +3728,29 @@ shada_read_next_item_start:
       garray_T ad_ga;
       ga_init(&ad_ga, sizeof(*(unpacked.data.via.map.ptr)), 1);
       for (size_t i = 0; i < unpacked.data.via.map.size; i++) {
-        CHECK_KEY_IS_STR("search pattern")
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_MAGIC,
+        CHECK_KEY_IS_STR(unpacked, "search pattern")
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_MAGIC,
                     entry->data.search_pattern.magic)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_SMARTCASE,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_SMARTCASE,
                     entry->data.search_pattern.smartcase)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_HAS_LINE_OFFSET,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_HAS_LINE_OFFSET,
                     entry->data.search_pattern.has_line_offset)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_PLACE_CURSOR_AT_END,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_PLACE_CURSOR_AT_END,
                     entry->data.search_pattern.place_cursor_at_end)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_IS_LAST_USED,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_IS_LAST_USED,
                     entry->data.search_pattern.is_last_used)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_IS_SUBSTITUTE_PATTERN,
+        BOOLEAN_KEY(unpacked, "search pattern",
+                    SEARCH_KEY_IS_SUBSTITUTE_PATTERN,
                     entry->data.search_pattern.is_substitute_pattern)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_HIGHLIGHTED,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_HIGHLIGHTED,
                     entry->data.search_pattern.highlighted)
-        BOOLEAN_KEY("search pattern", SEARCH_KEY_BACKWARD,
+        BOOLEAN_KEY(unpacked, "search pattern", SEARCH_KEY_BACKWARD,
                     entry->data.search_pattern.search_backward)
-        INTEGER_KEY("search pattern", SEARCH_KEY_OFFSET,
+        INTEGER_KEY(unpacked, "search pattern", SEARCH_KEY_OFFSET,
                     entry->data.search_pattern.offset)
-        CONVERTED_STRING_KEY("search pattern", SEARCH_KEY_PAT,
+        CONVERTED_STRING_KEY(unpacked, "search pattern", SEARCH_KEY_PAT,
                              entry->data.search_pattern.pat)
-        ADDITIONAL_KEY
+        ADDITIONAL_KEY(unpacked)
       }
       if (entry->data.search_pattern.pat == NULL) {
         emsgf(_(READERR("search pattern", "has no pattern")), initial_fpos);
@@ -3768,7 +3771,7 @@ shada_read_next_item_start:
       garray_T ad_ga;
       ga_init(&ad_ga, sizeof(*(unpacked.data.via.map.ptr)), 1);
       for (size_t i = 0; i < unpacked.data.via.map.size; i++) {
-        CHECK_KEY_IS_STR("mark")
+        CHECK_KEY_IS_STR(unpacked, "mark")
         if (CHECK_KEY(unpacked.data.via.map.ptr[i].key, KEY_NAME_CHAR)) {
           if (type_u64 == kSDItemJump || type_u64 == kSDItemChange) {
             emsgf(_(READERR("mark", "has n key which is only valid for "
@@ -3782,10 +3785,10 @@ shada_read_next_item_start:
               "mark", unpacked.data.via.map.ptr[i].val,
               entry->data.filemark.name, u64, TOCHAR);
         }
-        LONG_KEY("mark", KEY_LNUM, entry->data.filemark.mark.lnum)
-        INTEGER_KEY("mark", KEY_COL, entry->data.filemark.mark.col)
-        STRING_KEY("mark", KEY_FILE, entry->data.filemark.fname)
-        ADDITIONAL_KEY
+        LONG_KEY(unpacked, "mark", KEY_LNUM, entry->data.filemark.mark.lnum)
+        INTEGER_KEY(unpacked, "mark", KEY_COL, entry->data.filemark.mark.col)
+        STRING_KEY(unpacked, "mark", KEY_FILE, entry->data.filemark.fname)
+        ADDITIONAL_KEY(unpacked)
       }
       if (entry->data.filemark.fname == NULL) {
         emsgf(_(READERR("mark", "is missing file name")), initial_fpos);
@@ -3810,7 +3813,7 @@ shada_read_next_item_start:
       garray_T ad_ga;
       ga_init(&ad_ga, sizeof(*(unpacked.data.via.map.ptr)), 1);
       for (size_t i = 0; i < unpacked.data.via.map.size; i++) {
-        CHECK_KEY_IS_STR("register")
+        CHECK_KEY_IS_STR(unpacked, "register")
         if (CHECK_KEY(unpacked.data.via.map.ptr[i].key,
                       REG_KEY_CONTENTS)) {
           if (unpacked.data.via.map.ptr[i].val.type != MSGPACK_OBJECT_ARRAY) {
@@ -3828,8 +3831,8 @@ shada_read_next_item_start:
           }
           const msgpack_object_array arr =
               unpacked.data.via.map.ptr[i].val.via.array;
-          for (size_t i = 0; i < arr.size; i++) {
-            if (arr.ptr[i].type != MSGPACK_OBJECT_BIN) {
+          for (size_t j = 0; j < arr.size; j++) {
+            if (arr.ptr[j].type != MSGPACK_OBJECT_BIN) {
               emsgf(_(READERR("register", "has " REG_KEY_CONTENTS " array "
                               "with non-binary value")), initial_fpos);
               CLEAR_GA_AND_ERROR_OUT(ad_ga);
@@ -3837,18 +3840,19 @@ shada_read_next_item_start:
           }
           entry->data.reg.contents_size = arr.size;
           entry->data.reg.contents = xmalloc(arr.size * sizeof(char *));
-          for (size_t i = 0; i < arr.size; i++) {
-            entry->data.reg.contents[i] = BIN_CONVERTED(arr.ptr[i].via.bin);
+          for (size_t j = 0; j < arr.size; j++) {
+            entry->data.reg.contents[j] = BIN_CONVERTED(arr.ptr[j].via.bin);
           }
         }
-        BOOLEAN_KEY("register", REG_KEY_UNNAMED, entry->data.reg.is_unnamed)
-        TYPED_KEY("register", REG_KEY_TYPE, "an unsigned integer",
+        BOOLEAN_KEY(unpacked, "register", REG_KEY_UNNAMED,
+                    entry->data.reg.is_unnamed)
+        TYPED_KEY(unpacked, "register", REG_KEY_TYPE, "an unsigned integer",
                   entry->data.reg.type, POSITIVE_INTEGER, u64, TOU8)
-        TYPED_KEY("register", KEY_NAME_CHAR, "an unsigned integer",
+        TYPED_KEY(unpacked, "register", KEY_NAME_CHAR, "an unsigned integer",
                   entry->data.reg.name, POSITIVE_INTEGER, u64, TOCHAR)
-        TYPED_KEY("register", REG_KEY_WIDTH, "an unsigned integer",
+        TYPED_KEY(unpacked, "register", REG_KEY_WIDTH, "an unsigned integer",
                   entry->data.reg.width, POSITIVE_INTEGER, u64, TOSIZE)
-        ADDITIONAL_KEY
+        ADDITIONAL_KEY(unpacked)
       }
       if (entry->data.reg.contents == NULL) {
         emsgf(_(READERR("register", "has missing " REG_KEY_CONTENTS " array")),
@@ -3990,8 +3994,7 @@ shada_read_next_item_start:
           .data = unpacked.data.via.array.ptr[i],
         };
         {
-          msgpack_unpacked unpacked = unpacked_2;
-          if (unpacked.data.type != MSGPACK_OBJECT_MAP) {
+          if (unpacked_2.data.type != MSGPACK_OBJECT_MAP) {
             emsgf(_(RERR "Error while reading ShaDa file: "
                     "buffer list at position %" PRIu64 " "
                     "contains entry that is not a dictionary"),
@@ -4000,21 +4003,23 @@ shada_read_next_item_start:
           }
           entry->data.buffer_list.buffers[i].pos = default_pos;
           garray_T ad_ga;
-          ga_init(&ad_ga, sizeof(*(unpacked.data.via.map.ptr)), 1);
+          ga_init(&ad_ga, sizeof(*(unpacked_2.data.via.map.ptr)), 1);
           {
+            // XXX: Temporarily reassign `i` because the macros depend on it.
             const size_t j = i;
             {
-              for (size_t i = 0; i < unpacked.data.via.map.size; i++) {
-                CHECK_KEY_IS_STR("buffer list entry")
-                LONG_KEY("buffer list entry", KEY_LNUM,
+              for (i = 0; i < unpacked_2.data.via.map.size; i++) {
+                CHECK_KEY_IS_STR(unpacked_2, "buffer list entry")
+                LONG_KEY(unpacked_2, "buffer list entry", KEY_LNUM,
                          entry->data.buffer_list.buffers[j].pos.lnum)
-                INTEGER_KEY("buffer list entry", KEY_COL,
+                INTEGER_KEY(unpacked_2, "buffer list entry", KEY_COL,
                             entry->data.buffer_list.buffers[j].pos.col)
-                STRING_KEY("buffer list entry", KEY_FILE,
+                STRING_KEY(unpacked_2, "buffer list entry", KEY_FILE,
                            entry->data.buffer_list.buffers[j].fname)
-                ADDITIONAL_KEY
+                ADDITIONAL_KEY(unpacked_2)
               }
             }
+            i = j;  // XXX: Restore `i`.
           }
           if (entry->data.buffer_list.buffers[i].pos.lnum <= 0) {
             emsgf(_(RERR "Error while reading ShaDa file: "
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index 518bd0922e..a9330e792a 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -2112,9 +2112,9 @@ char_u *did_set_spelllang(win_T *wp)
         }
 
         if (region_mask != 0) {
-          langp_T *p = GA_APPEND_VIA_PTR(langp_T, &ga);
-          p->lp_slang = slang;
-          p->lp_region = region_mask;
+          langp_T *p_ = GA_APPEND_VIA_PTR(langp_T, &ga);
+          p_->lp_slang = slang;
+          p_->lp_region = region_mask;
 
           use_midword(slang, wp);
           if (slang->sl_nobreak)
@@ -2190,11 +2190,11 @@ char_u *did_set_spelllang(win_T *wp)
       }
 
       if (region_mask != 0) {
-        langp_T *p = GA_APPEND_VIA_PTR(langp_T, &ga);
-        p->lp_slang = slang;
-        p->lp_sallang = NULL;
-        p->lp_replang = NULL;
-        p->lp_region = region_mask;
+        langp_T *p_ = GA_APPEND_VIA_PTR(langp_T, &ga);
+        p_->lp_slang = slang;
+        p_->lp_sallang = NULL;
+        p_->lp_replang = NULL;
+        p_->lp_region = region_mask;
 
         use_midword(slang, wp);
       }
diff --git a/src/nvim/spellfile.c b/src/nvim/spellfile.c
index 8be8d24b9f..7a6f2fce39 100644
--- a/src/nvim/spellfile.c
+++ b/src/nvim/spellfile.c
@@ -4311,8 +4311,8 @@ static int write_vim_spell(spellinfo_T *spin, char_u *fname)
       qsort(gap->ga_data, (size_t)gap->ga_len,
           sizeof(fromto_T), rep_compare);
 
-    int i = round == 1 ? SN_REP : (round == 2 ? SN_SAL : SN_REPSAL);
-    putc(i, fd);                                        // <sectionID>
+    int sect_id = round == 1 ? SN_REP : (round == 2 ? SN_SAL : SN_REPSAL);
+    putc(sect_id, fd);                                  // <sectionID>
 
     // This is for making suggestions, section is not required.
     putc(0, fd);                                        // <sectionflags>
diff --git a/src/nvim/syntax.c b/src/nvim/syntax.c
index 973d09d065..81c78ca6a9 100644
--- a/src/nvim/syntax.c
+++ b/src/nvim/syntax.c
@@ -6463,7 +6463,7 @@ void do_highlight(const char *line, const bool forceit, const bool init)
 
   // If no argument, list current highlighting.
   if (ends_excmd((uint8_t)(*line))) {
-    for (int i = 1; i <= highlight_ga.ga_len && !got_int; i++) {
+    for (i = 1; i <= highlight_ga.ga_len && !got_int; i++) {
       // TODO(brammool): only call when the group has attributes set
       highlight_list_one(i);
     }
@@ -6569,8 +6569,8 @@ void do_highlight(const char *line, const bool forceit, const bool init)
       restore_cterm_colors();
 
       // Clear all default highlight groups and load the defaults.
-      for (int idx = 0; idx < highlight_ga.ga_len; idx++) {
-        highlight_clear(idx);
+      for (int j = 0; j < highlight_ga.ga_len; j++) {
+        highlight_clear(j);
       }
       init_highlight(true, true);
       highlight_changed();
diff --git a/src/nvim/terminal.c b/src/nvim/terminal.c
index f715344689..51bf22b31c 100644
--- a/src/nvim/terminal.c
+++ b/src/nvim/terminal.c
@@ -529,6 +529,20 @@ void terminal_send(Terminal *term, char *data, size_t size)
   term->opts.write_cb(data, size, term->opts.data);
 }
 
+void terminal_paste(long count, char_u **y_array, size_t y_size)
+{
+  for (int i = 0; i < count; i++) {  // -V756
+    // feed the lines to the terminal
+    for (size_t j = 0; j < y_size; j++) {
+      if (j) {
+        // terminate the previous line
+        terminal_send(curbuf->terminal, "\n", 1);
+      }
+      terminal_send(curbuf->terminal, (char *)y_array[j], STRLEN(y_array[j]));
+    }
+  }
+}
+
 void terminal_flush_output(Terminal *term)
 {
   size_t len = vterm_output_read(term->vt, term->textbuf,
diff --git a/src/nvim/tui/input.c b/src/nvim/tui/input.c
index 0362820687..a0df80a8e8 100644
--- a/src/nvim/tui/input.c
+++ b/src/nvim/tui/input.c
@@ -352,8 +352,8 @@ static bool handle_forced_escape(TermInput *input)
   return false;
 }
 
-static void read_cb(Stream *stream, RBuffer *buf, size_t c, void *data,
-    bool eof)
+static void read_cb(Stream *stream, RBuffer *buf, size_t count_, void *data,
+                    bool eof)
 {
   TermInput *input = data;
 
diff --git a/src/nvim/ui.c b/src/nvim/ui.c
index 9c91192a8b..96232ab223 100644
--- a/src/nvim/ui.c
+++ b/src/nvim/ui.c
@@ -51,10 +51,10 @@
 static UI *uis[MAX_UI_COUNT];
 static bool ui_ext[kUIExtCount] = { 0 };
 static size_t ui_count = 0;
-static int row = 0, col = 0;
+static int ui_mode_idx = SHAPE_IDX_N;
+static int cursor_row = 0, cursor_col = 0;
 static bool pending_cursor_update = false;
 static int busy = 0;
-static int mode_idx = SHAPE_IDX_N;
 static bool pending_mode_info_update = false;
 static bool pending_mode_update = false;
 static handle_T cursor_grid_handle = DEFAULT_GRID_HANDLE;
@@ -189,12 +189,12 @@ void ui_refresh(void)
     UI *ui = uis[i];
     width = MIN(ui->width, width);
     height = MIN(ui->height, height);
-    for (UIExtension i = 0; (int)i < kUIExtCount; i++) {
-      ext_widgets[i] &= ui->ui_ext[i];
+    for (UIExtension j = 0; (int)j < kUIExtCount; j++) {
+      ext_widgets[j] &= ui->ui_ext[j];
     }
   }
 
-  row = col = 0;
+  cursor_row = cursor_col = 0;
   pending_cursor_update = true;
 
   for (UIExtension i = 0; (int)i < kUIExtCount; i++) {
@@ -327,9 +327,9 @@ void ui_line(ScreenGrid *grid, int row, int startcol, int endcol, int clearcol,
           (const sattr_T *)grid->attrs + off);
 
   if (p_wd) {  // 'writedelay': flush & delay each time.
-    int old_row = row, old_col = col;
+    int old_row = cursor_row, old_col = cursor_col;
     handle_T old_grid = cursor_grid_handle;
-    // If'writedelay is active, we set the cursor to highlight what was drawn
+    // If 'writedelay' is active, set the cursor to indicate what was drawn.
     ui_grid_cursor_goto(grid->handle, row, MIN(clearcol, (int)Columns-1));
     ui_flush();
     uint64_t wd = (uint64_t)labs(p_wd);
@@ -345,12 +345,14 @@ void ui_cursor_goto(int new_row, int new_col)
 
 void ui_grid_cursor_goto(handle_T grid_handle, int new_row, int new_col)
 {
-  if (new_row == row && new_col == col && grid_handle == cursor_grid_handle) {
+  if (new_row == cursor_row
+      && new_col == cursor_col
+      && grid_handle == cursor_grid_handle) {
     return;
   }
 
-  row = new_row;
-  col = new_col;
+  cursor_row = new_row;
+  cursor_col = new_col;
   cursor_grid_handle = grid_handle;
   pending_cursor_update = true;
 }
@@ -362,12 +364,12 @@ void ui_mode_info_set(void)
 
 int ui_current_row(void)
 {
-  return row;
+  return cursor_row;
 }
 
 int ui_current_col(void)
 {
-  return col;
+  return cursor_col;
 }
 
 void ui_flush(void)
@@ -375,7 +377,7 @@ void ui_flush(void)
   cmdline_ui_flush();
   win_ui_flush();
   if (pending_cursor_update) {
-    ui_call_grid_cursor_goto(cursor_grid_handle, row, col);
+    ui_call_grid_cursor_goto(cursor_grid_handle, cursor_row, cursor_col);
     pending_cursor_update = false;
   }
   if (pending_mode_info_update) {
@@ -386,8 +388,8 @@ void ui_flush(void)
     pending_mode_info_update = false;
   }
   if (pending_mode_update) {
-    char *full_name = shape_table[mode_idx].full_name;
-    ui_call_mode_change(cstr_as_string(full_name), mode_idx);
+    char *full_name = shape_table[ui_mode_idx].full_name;
+    ui_call_mode_change(cstr_as_string(full_name), ui_mode_idx);
     pending_mode_update = false;
   }
   ui_call_flush();
@@ -403,8 +405,8 @@ void ui_cursor_shape(void)
   }
   int new_mode_idx = cursor_get_mode_idx();
 
-  if (new_mode_idx != mode_idx) {
-    mode_idx = new_mode_idx;
+  if (new_mode_idx != ui_mode_idx) {
+    ui_mode_idx = new_mode_idx;
     pending_mode_update = true;
   }
   conceal_check_cursor_line();