vi: fix incorrect memory access on brace matching. Closes 7256

While at it, fix brace matching to actually show the match
(missed fflush was causing cursor positioning to be buffered);
shorten brace matching code; remove unused macro indirection
in indicate_error().

Custom linker script 'busybox_ldscript' found, using it
function                                             old     new   delta
indicate_error                                         -      61     +61
mysleep                                               43      56     +13
char_insert                                          483     486      +3
find_pair                                            167     124     -43
Indicate_Error                                        61       -     -61
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 2/1 up/down: 77/-104)           Total: -27 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 36 insertions, 43 deletions

diff --git a/editors/vi.c b/editors/vi.c
index 24a9f60a8..70bdbab07 100644
--- a/editors/vi.c
+++ b/editors/vi.c
@@ -566,8 +566,7 @@ static void redraw(int);	// force a full screen refresh
 static char* format_line(char* /*, int*/);
 static void refresh(int);       // update the terminal from screen[]
 
-static void Indicate_Error(void);       // use flash or beep to indicate error
-#define indicate_error(c) Indicate_Error()
+static void indicate_error(void);       // use flash or beep to indicate error
 static void Hit_Return(void);
 
 #if ENABLE_FEATURE_VI_SEARCH
@@ -1840,11 +1839,11 @@ static char *bound_dot(char *p) // make sure  text[0] <= P < "end"
 {
         if (p >= end && end > text) {
                 p = end - 1;
-                indicate_error('1');
+                indicate_error();
         }
         if (p < text) {
                 p = text;
-                indicate_error('2');
+                indicate_error();
         }
         return p;
 }
@@ -2023,16 +2022,9 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
                         p = text_hole_delete(p, p, ALLOW_UNDO_QUEUED);  // shrink buffer 1 char
                 }
         } else {
-#if ENABLE_FEATURE_VI_SETOPTS
                 // insert a char into text[]
-                char *sp;               // "save p"
-#endif
-
                 if (c == 13)
                         c = '\n';       // translate \r to \n
-#if ENABLE_FEATURE_VI_SETOPTS
-                sp = p;                 // remember addr of insert
-#endif
 #if ENABLE_FEATURE_VI_UNDO
 # if ENABLE_FEATURE_VI_UNDO_QUEUE
                 if (c == '\n')
@@ -2056,8 +2048,8 @@ static char *char_insert(char *p, char c, int undo) // insert the char c at 'p'
 #endif /* ENABLE_FEATURE_VI_UNDO */
                 p += 1 + stupid_insert(p, c);   // insert the char
 #if ENABLE_FEATURE_VI_SETOPTS
-                if (showmatch && strchr(")]}", *sp) != NULL) {
-                        showmatching(sp);
+                if (showmatch && strchr(")]}", c) != NULL) {
+                        showmatching(p - 1);
                 }
                 if (autoindent && c == '\n') {  // auto indent the new line
                         char *q;
@@ -2217,34 +2209,32 @@ static char *skip_thing(char *p, int linecnt, int dir, int type)
 }
 
 // find matching char of pair  ()  []  {}
+// will crash if c is not one of these
 static char *find_pair(char *p, const char c)
 {
-        char match, *q;
+        const char *braces = "()[]{}";
+        char match;
         int dir, level;
 
-        match = ')';
+        dir = strchr(braces, c) - braces;
+        dir ^= 1;
+        match = braces[dir];
+        dir = ((dir & 1) << 1) - 1; /* 1 for ([{, -1 for )\} */
+
+        // look for match, count levels of pairs  (( ))
         level = 1;
-        dir = 1;                        // assume forward
-        switch (c) {
-        case '(': match = ')'; break;
-        case '[': match = ']'; break;
-        case '{': match = '}'; break;
-        case ')': match = '('; dir = -1; break;
-        case ']': match = '['; dir = -1; break;
-        case '}': match = '{'; dir = -1; break;
-        }
-        for (q = p + dir; text <= q && q < end; q += dir) {
-                // look for match, count levels of pairs  (( ))
-                if (*q == c)
+        for (;;) {
+                p += dir;
+                if (p < text || p >= end)
+                        return NULL;
+                if (*p == c)
                         level++;        // increase pair levels
-                if (*q == match)
+                if (*p == match) {
                         level--;        // reduce pair level
-                if (level == 0)
-                        break;          // found matching pair
+                        if (level == 0)
+                                return p; // found matching pair
+                }
         }
-        if (level != 0)
-                q = NULL;               // indicate no match
-        return q;
 }
 
 #if ENABLE_FEATURE_VI_SETOPTS
@@ -2256,7 +2246,7 @@ static void showmatching(char *p)
         // we found half of a pair
         q = find_pair(p, *p);   // get loc of matching char
         if (q == NULL) {
-                indicate_error('3');    // no matching char
+                indicate_error();       // no matching char
         } else {
                 // "q" now points to matching pair
                 save_dot = dot; // remember where we are
@@ -2815,6 +2805,9 @@ static int mysleep(int hund)	// sleep for 'hund' 1/100 seconds or stdin ready
 {
         struct pollfd pfd[1];
 
+        if (hund != 0)
+                fflush_all();
+
         pfd[0].fd = STDIN_FILENO;
         pfd[0].events = POLLIN;
         return safe_poll(pfd, 1, hund*10) > 0;
@@ -3059,7 +3052,7 @@ static void flash(int h)
         redraw(TRUE);
 }
 
-static void Indicate_Error(void)
+static void indicate_error(void)
 {
 #if ENABLE_FEATURE_VI_CRASHME
         if (crashme > 0)
@@ -3602,7 +3595,7 @@ static void do_cmd(int c)
                 break;
         case 27:                        // esc
                 if (cmd_mode == 0)
-                        indicate_error(c);
+                        indicate_error();
                 cmd_mode = 0;   // stop insrting
                 undo_queue_commit();
                 end_cmd_q();
@@ -3621,7 +3614,7 @@ static void do_cmd(int c)
                 if ((unsigned)c1 <= 25) { // a-z?
                         YDreg = c1;
                 } else {
-                        indicate_error(c);
+                        indicate_error();
                 }
                 break;
         case '\'':                      // '- goto a specific mark
@@ -3639,7 +3632,7 @@ static void do_cmd(int c)
                         dot_begin();    // go to B-o-l
                         dot_skip_over_ws();
                 } else {
-                        indicate_error(c);
+                        indicate_error();
                 }
                 break;
         case 'm':                       // m- Mark a line
@@ -3652,7 +3645,7 @@ static void do_cmd(int c)
                         // remember the line
                         mark[c1] = dot;
                 } else {
-                        indicate_error(c);
+                        indicate_error();
                 }
                 break;
         case 'P':                       // P- Put register before
@@ -3713,7 +3706,7 @@ static void do_cmd(int c)
                                 // we found half of a pair
                                 p = find_pair(q, *q);
                                 if (p == NULL) {
-                                        indicate_error(c);
+                                        indicate_error();
                                 } else {
                                         dot = p;
                                 }
@@ -3721,7 +3714,7 @@ static void do_cmd(int c)
                         }
                 }
                 if (*q == '\n')
-                        indicate_error(c);
+                        indicate_error();
                 break;
         case 'f':                       // f- forward to a user specified char
                 last_forward_char = get_one_char();     // get the search char
@@ -4054,7 +4047,7 @@ static void do_cmd(int c)
                 // ZZ means to save file (if necessary), then exit
                 c1 = get_one_char();
                 if (c1 != 'Z') {
-                        indicate_error(c);
+                        indicate_error();
                         break;
                 }
                 if (modified_count) {
@@ -4138,7 +4131,7 @@ static void do_cmd(int c)
                         // could not recognize object
                         c = c1 = 27;    // error-
                         ml = 0;
-                        indicate_error(c);
+                        indicate_error();
                 }
                 if (ml && whole) {
                         if (c == 'c') {