fix(options): use a union for def_val (#27169)

Problem:
APIs get wrong boolean option default values on big-endian platforms.

Solution:
Use a union for def_val.
Cannot use OptVal or OptValData yet as it needs to have the same types
as option variables.

src/nvim/generators/gen_options.lua

@@ -125,31 +125,27 @@ local function get_cond(c, base_string)
   return cond_string
 end
 
-local value_dumpers = {
-  ['function'] = function(v)
-    return v()
-  end,
-  string = cstr,
-  boolean = function(v)
-    return v and 'true' or 'false'
-  end,
-  number = function(v)
-    return ('%iL'):format(v)
-  end,
-  ['nil'] = function(_)
-    return '0'
-  end,
-}
-
-local get_value = function(v)
-  return '(void *) ' .. value_dumpers[type(v)](v)
-end
-
 local get_defaults = function(d, n)
   if d == nil then
     error("option '" .. n .. "' should have a default value")
   end
-  return get_value(d)
+
+  local value_dumpers = {
+    ['function'] = function(v)
+      return v()
+    end,
+    string = function(v)
+      return '.string=' .. cstr(v)
+    end,
+    boolean = function(v)
+      return '.boolean=' .. (v and 'true' or 'false')
+    end,
+    number = function(v)
+      return ('.number=%iL'):format(v)
+    end,
+  }
+
+  return value_dumpers[type(d)](d)
 end
 
 --- @type {[1]:string,[2]:string}[]
@@ -213,11 +209,11 @@ local function dump_option(i, o)
     if o.defaults.condition then
       w(get_cond(o.defaults.condition))
     end
-    w('    .def_val=' .. get_defaults(o.defaults.if_true, o.full_name))
+    w('    .def_val' .. get_defaults(o.defaults.if_true, o.full_name))
     if o.defaults.condition then
       if o.defaults.if_false then
         w('#else')
-        w('    .def_val=' .. get_defaults(o.defaults.if_false, o.full_name))
+        w('    .def_val' .. get_defaults(o.defaults.if_false, o.full_name))
       end
       w('#endif')
     end

src/nvim/option.c

@@ -174,7 +174,7 @@ static int p_paste_dep_opts[] = {
 void set_init_tablocal(void)
 {
   // susy baka: cmdheight calls itself OPT_GLOBAL but is really tablocal!
-  p_ch = (OptInt)(intptr_t)options[kOptCmdheight].def_val;
+  p_ch = options[kOptCmdheight].def_val.number;
 }
 
 /// Initialize the 'shell' option to a default value.
@@ -275,13 +275,8 @@ static void set_init_default_cdpath(void)
     }
   }
   buf[j] = NUL;
-  OptIndex opt_idx = kOptCdpath;
+  options[kOptCdpath].def_val.string = buf;
-  if (opt_idx != kOptInvalid) {
+  options[kOptCdpath].flags |= P_DEF_ALLOCED;
-    options[opt_idx].def_val = buf;
-    options[opt_idx].flags |= P_DEF_ALLOCED;
-  } else {
-    xfree(buf);           // cannot happen
-  }
   xfree(cdpath);
 }
 
@@ -309,9 +304,9 @@ static void set_init_expand_env(void)
       p = xstrdup(p);
       *(char **)opt->var = p;
       if (opt->flags & P_DEF_ALLOCED) {
-        xfree(opt->def_val);
+        xfree(opt->def_val.string);
       }
-      opt->def_val = p;
+      opt->def_val.string = p;
       opt->flags |= P_DEF_ALLOCED;
     }
   }
@@ -438,19 +433,19 @@ static void set_option_default(const OptIndex opt_idx, int opt_flags)
       // Use set_string_option_direct() for local options to handle freeing and allocating the
       // value.
       if (opt->indir != PV_NONE) {
-        set_string_option_direct(opt_idx, opt->def_val, opt_flags, 0);
+        set_string_option_direct(opt_idx, opt->def_val.string, opt_flags, 0);
       } else {
         if (flags & P_ALLOCED) {
           free_string_option(*(char **)(varp));
         }
-        *(char **)varp = opt->def_val;
+        *(char **)varp = opt->def_val.string;
         opt->flags &= ~P_ALLOCED;
       }
     } else if (option_has_type(opt_idx, kOptValTypeNumber)) {
       if (opt->indir == PV_SCROLL) {
         win_comp_scroll(curwin);
       } else {
-        OptInt def_val = (OptInt)(intptr_t)opt->def_val;
+        OptInt def_val = opt->def_val.number;
         if ((OptInt *)varp == &curwin->w_p_so
             || (OptInt *)varp == &curwin->w_p_siso) {
           // 'scrolloff' and 'sidescrolloff' local values have a
@@ -465,7 +460,7 @@ static void set_option_default(const OptIndex opt_idx, int opt_flags)
         }
       }
     } else {  // boolean
-      *(int *)varp = (int)(intptr_t)opt->def_val;
+      *(int *)varp = opt->def_val.boolean;
 #ifdef UNIX
       // 'modeline' defaults to off for root
       if (opt->indir == PV_ML && getuid() == ROOT_UID) {
@@ -521,10 +516,10 @@ static void set_string_default(OptIndex opt_idx, char *val, bool allocated)
 
   vimoption_T *opt = &options[opt_idx];
   if (opt->flags & P_DEF_ALLOCED) {
-    xfree(opt->def_val);
+    xfree(opt->def_val.string);
   }
 
-  opt->def_val = allocated ? val : xstrdup(val);
+  opt->def_val.string = allocated ? val : xstrdup(val);
   opt->flags |= P_DEF_ALLOCED;
 }
 
@@ -564,7 +559,7 @@ static char *find_dup_item(char *origval, const char *newval, uint32_t flags)
 void set_number_default(OptIndex opt_idx, OptInt val)
 {
   if (opt_idx != kOptInvalid) {
-    options[opt_idx].def_val = (void *)(intptr_t)val;
+    options[opt_idx].def_val.number = val;
   }
 }
 
@@ -639,11 +634,11 @@ void set_init_3(void)
         || path_fnamecmp(p, "tcsh") == 0) {
       if (do_sp) {
         p_sp = "|& tee";
-        options[kOptShellpipe].def_val = p_sp;
+        options[kOptShellpipe].def_val.string = p_sp;
       }
       if (do_srr) {
         p_srr = ">&";
-        options[kOptShellredir].def_val = p_srr;
+        options[kOptShellredir].def_val.string = p_srr;
       }
     } else if (path_fnamecmp(p, "sh") == 0
                || path_fnamecmp(p, "ksh") == 0
@@ -658,11 +653,11 @@ void set_init_3(void)
       // Always use POSIX shell style redirection if we reach this
       if (do_sp) {
         p_sp = "2>&1| tee";
-        options[kOptShellpipe].def_val = p_sp;
+        options[kOptShellpipe].def_val.string = p_sp;
       }
       if (do_srr) {
         p_srr = ">%s 2>&1";
-        options[kOptShellredir].def_val = p_srr;
+        options[kOptShellredir].def_val.string = p_srr;
       }
     }
     xfree(p);
@@ -724,12 +719,12 @@ void set_title_defaults(void)
   // icon name.  Saves a bit of time, because the X11 display server does
   // not need to be contacted.
   if (!(options[kOptTitle].flags & P_WAS_SET)) {
-    options[kOptTitle].def_val = 0;
+    options[kOptTitle].def_val.boolean = false;
-    p_title = 0;
+    p_title = false;
   }
   if (!(options[kOptIcon].flags & P_WAS_SET)) {
-    options[kOptIcon].def_val = 0;
+    options[kOptIcon].def_val.boolean = false;
-    p_icon = 0;
+    p_icon = false;
   }
 }
 
@@ -751,7 +746,7 @@ void ex_set(exarg_T *eap)
 /// Get the default value for a string option.
 static char *stropt_get_default_val(OptIndex opt_idx, uint64_t flags)
 {
-  char *newval = options[opt_idx].def_val;
+  char *newval = options[opt_idx].def_val.string;
   // expand environment variables and ~ since the default value was
   // already expanded, only required when an environment variable was set
   // later
@@ -1178,7 +1173,7 @@ static OptVal get_option_newval(OptIndex opt_idx, int opt_flags, set_prefix_T pr
         break;
       }
     } else if (nextchar == '&') {
-      newval_bool = TRISTATE_FROM_INT((int)(intptr_t)options[opt_idx].def_val);
+      newval_bool = TRISTATE_FROM_INT(options[opt_idx].def_val.boolean);
     } else if (nextchar == '<') {
       // For 'autoread', kNone means to use global value.
       if ((int *)varp == &curbuf->b_p_ar && opt_flags == OPT_LOCAL) {
@@ -1212,7 +1207,7 @@ static OptVal get_option_newval(OptIndex opt_idx, int opt_flags, set_prefix_T pr
     // other        error
     arg++;
     if (nextchar == '&') {
-      newval_num = (OptInt)(intptr_t)options[opt_idx].def_val;
+      newval_num = options[opt_idx].def_val.number;
     } else if (nextchar == '<') {
       if ((OptInt *)varp == &curbuf->b_p_ul && opt_flags == OPT_LOCAL) {
         // for 'undolevels' NO_LOCAL_UNDOLEVEL means using the global newval_num
@@ -5311,7 +5306,7 @@ void reset_modifiable(void)
 {
   curbuf->b_p_ma = false;
   p_ma = false;
-  options[kOptModifiable].def_val = false;
+  options[kOptModifiable].def_val.boolean = false;
 }
 
 /// Set the global value for 'iminsert' to the local value.

src/nvim/option.h

@@ -60,7 +60,12 @@ typedef struct {
   opt_expand_cb_T opt_expand_cb;
 
   // TODO(famiu): Use OptVal for def_val.
-  void *def_val;     ///< default values for variable (neovim!!)
+  union {
+    int boolean;
+    OptInt number;
+    char *string;
+  } def_val;         ///< default value for variable
+
   LastSet last_set;  ///< script in which the option was last set
 } vimoption_T;
 

src/nvim/options.lua

@@ -61,7 +61,7 @@ end
 --- @return fun(): string
 local function macros(s)
   return function()
-    return s
+    return '.string=' .. s
   end
 end
 
@@ -69,7 +69,7 @@ end
 --- @return fun(): string
 local function imacros(s)
   return function()
-    return '(intptr_t)' .. s
+    return '.number=' .. s
   end
 end
 
@@ -1271,7 +1271,7 @@ return {
       abbreviation = 'co',
       cb = 'did_set_lines_or_columns',
       defaults = {
-        if_true = macros('DFLT_COLS'),
+        if_true = imacros('DFLT_COLS'),
         doc = '80 or terminal width',
       },
       desc = [=[
@@ -4024,7 +4024,7 @@ return {
     {
       abbreviation = 'imi',
       cb = 'did_set_iminsert',
-      defaults = { if_true = macros('B_IMODE_NONE') },
+      defaults = { if_true = imacros('B_IMODE_NONE') },
       desc = [=[
         Specifies whether :lmap or an Input Method (IM) is to be used in
         Insert mode.  Valid values:
@@ -4050,7 +4050,7 @@ return {
     },
     {
       abbreviation = 'ims',
-      defaults = { if_true = macros('B_IMODE_USE_INSERT') },
+      defaults = { if_true = imacros('B_IMODE_USE_INSERT') },
       desc = [=[
         Specifies whether :lmap or an Input Method (IM) is to be used when
         entering a search pattern.  Valid values:
@@ -4747,7 +4747,7 @@ return {
     {
       cb = 'did_set_lines_or_columns',
       defaults = {
-        if_true = macros('DFLT_ROWS'),
+        if_true = imacros('DFLT_ROWS'),
         doc = '24 or terminal height',
       },
       desc = [=[