Remove POSIX 'cpoptions': '\'

runtime/doc/options.txt

@@ -1945,14 +1945,6 @@ A jump table for the options with a short description can be found at |Q_op|.
 	POSIX flags.  These are not included in the Vi default value, except
 	when $VIM_POSIX was set on startup. |posix|
 
-	    contains	behavior	~
-								*cpo-\*
-		\	Backslash in a [] range in a search pattern is taken
-			literally, only "\]" is special  See |/[]|
-			   '\' included: "/[ \-]"  finds <Space>, '\' and '-'
-			   '\' excluded: "/[ \-]"  finds <Space> and '-'
-			Also see |cpo-l|.
-
 						*'cryptmethod'* *'cm'*
 'cryptmethod'		Removed. |vim-differences| {Nvim}
 

src/nvim/option_defs.h

@@ -129,14 +129,13 @@
 #define CPO_SPECI       '<'     /* don't recognize <> in mappings */
 #define CPO_REGAPPEND   '>'     /* insert NL when appending to a register */
 /* POSIX flags */
-#define CPO_BACKSL      '\\'    /* \ is not special in [] */
 #define CPO_SCOLON      ';'     /* using "," and ";" will skip over char if
                                  * cursor would not move */
 /* default values for Vim, Vi and POSIX */
 #define CPO_VIM         "aABceFs"
 #define CPO_VI          "aAbBcCdDeEfFiIJkKlLmMnoOpPqrRsStuvWxXyZ$!%+<>;"
 #define CPO_ALL \
-  "aAbBcCdDeEfFiIJkKlLmMnoOpPqrRsStuvWxXyZ$!%+<>\\;"
+  "aAbBcCdDeEfFiIJkKlLmMnoOpPqrRsStuvWxXyZ$!%+<>;"
 
 /* characters for p_ww option: */
 #define WW_ALL          "bshl<>[],~"

src/nvim/regexp.c

@@ -1120,12 +1120,10 @@ static int get_coll_element(char_u **pp)
 }
 
 static int reg_cpo_lit; /* 'cpoptions' contains 'l' flag */
-static int reg_cpo_bsl; /* 'cpoptions' contains '\' flag */
 
 static void get_cpo_flags(void)
 {
   reg_cpo_lit = vim_strchr(p_cpo, CPO_LITERAL) != NULL;
-  reg_cpo_bsl = vim_strchr(p_cpo, CPO_BACKSL) != NULL;
 }
 
 /*
@@ -1149,7 +1147,6 @@ static char_u *skip_anyof(char_u *p)
       if (*p != ']' && *p != NUL)
         mb_ptr_adv(p);
     } else if (*p == '\\'
-               && !reg_cpo_bsl
                && (vim_strchr(REGEXP_INRANGE, p[1]) != NULL
                    || (!reg_cpo_lit && vim_strchr(REGEXP_ABBR, p[1]) != NULL)))
       p += 2;
@@ -2222,7 +2219,7 @@ collection:
               }
 
               /* Handle \o40, \x20 and \u20AC style sequences */
-              if (endc == '\\' && !reg_cpo_lit && !reg_cpo_bsl)
+              if (endc == '\\' && !reg_cpo_lit)
                 endc = coll_get_char();
 
               if (startc > endc)
@@ -2245,10 +2242,8 @@ collection:
            * Only "\]", "\^", "\]" and "\\" are special in Vi.  Vim
            * accepts "\t", "\e", etc., but only when the 'l' flag in
            * 'cpoptions' is not included.
-           * Posix doesn't recognize backslash at all.
            */
           else if (*regparse == '\\'
-                   && !reg_cpo_bsl
                    && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
                        || (!reg_cpo_lit
                            && vim_strchr(REGEXP_ABBR,

src/nvim/regexp_nfa.c

@@ -1584,10 +1584,8 @@ collection:
          * Only "\]", "\^", "\]" and "\\" are special in Vi.  Vim
          * accepts "\t", "\e", etc., but only when the 'l' flag in
          * 'cpoptions' is not included.
-         * Posix doesn't recognize backslash at all.
          */
         if (*regparse == '\\'
-            && !reg_cpo_bsl
             && regparse + 1 <= endp
             && (vim_strchr(REGEXP_INRANGE, regparse[1]) != NULL
                 || (!reg_cpo_lit