buffer: PVS/V557: Refactor maketitle()

src/nvim/buffer.c

@@ -2936,45 +2936,48 @@ void maketitle(void)
 
 #define SPACE_FOR_FNAME (sizeof(buf) - 100)
 #define SPACE_FOR_DIR   (sizeof(buf) - 20)
-#define SPACE_FOR_ARGNR (sizeof(buf) - 10)  // At least room for " - VIM".
+#define SPACE_FOR_ARGNR (sizeof(buf) - 10)  // At least room for " - NVIM".
+      char *buf_p = buf;
       if (curbuf->b_fname == NULL) {
-        xstrlcpy(buf, _("[No Name]"), SPACE_FOR_FNAME + 1);
+        const size_t size = xstrlcpy(buf_p, _("[No Name]"),
+                                     SPACE_FOR_FNAME + 1);
+        buf_p += MIN(size, SPACE_FOR_FNAME);
       } else {
-        transstr_buf((const char *)path_tail(curbuf->b_fname),
-                     buf, SPACE_FOR_FNAME + 1);
+        buf_p += transstr_buf((const char *)path_tail(curbuf->b_fname),
+                              buf_p, SPACE_FOR_FNAME + 1);
       }
 
       switch (bufIsChanged(curbuf)
               | (curbuf->b_p_ro << 1)
               | (!MODIFIABLE(curbuf) << 2)) {
         case 0: break;
-        case 1: strcat(buf, " +"); break;
-        case 2: strcat(buf, " ="); break;
-        case 3: strcat(buf, " =+"); break;
+        case 1: buf_p = strappend(buf_p, " +"); break;
+        case 2: buf_p = strappend(buf_p, " ="); break;
+        case 3: buf_p = strappend(buf_p, " =+"); break;
         case 4:
-        case 6: strcat(buf, " -"); break;
+        case 6: buf_p = strappend(buf_p, " -"); break;
         case 5:
-        case 7: strcat(buf, " -+"); break;
+        case 7: buf_p = strappend(buf_p, " -+"); break;
         default: assert(false);
       }
 
       if (curbuf->b_fname != NULL) {
         // Get path of file, replace home dir with ~.
-        size_t off = strlen(buf);
-        buf[off++] = ' ';
-        buf[off++] = '(';
-        home_replace(curbuf, curbuf->b_ffname,
-                     (char_u *)buf + off, (size_t)(SPACE_FOR_DIR - off), true);
+        *buf_p++ = ' ';
+        *buf_p++ = '(';
+        home_replace(curbuf, curbuf->b_ffname, (char_u *)buf_p,
+                     (SPACE_FOR_DIR - (size_t)(buf_p - buf)), true);
 #ifdef BACKSLASH_IN_FILENAME
-        /* avoid "c:/name" to be reduced to "c" */
-        if (isalpha(buf[off]) && buf[off + 1] == ':')
-          off += 2;
+        // Avoid "c:/name" to be reduced to "c".
+        if (isalpha((uint8_t)buf_p) && *(buf_p + 1) == ':') {
+          buf_p += 2;
+        }
 #endif
         // Remove the file name.
-        char *p = (char *)path_tail_with_sep((char_u *)buf + off);
-        if (p == buf + off) {
+        char *p = (char *)path_tail_with_sep((char_u *)buf_p);
+        if (p == buf_p) {
           // Must be a help buffer.
-          xstrlcpy(buf + off, _("help"), SPACE_FOR_DIR - off);
+          xstrlcpy(buf_p, _("help"), SPACE_FOR_DIR - (size_t)(buf_p - buf));
         } else {
           *p = NUL;
         }
@@ -2982,19 +2985,27 @@ void maketitle(void)
         // Translate unprintable chars and concatenate.  Keep some
         // room for the server name.  When there is no room (very long
         // file name) use (...).
-        if (off < SPACE_FOR_DIR) {
-          p = transstr(buf + off);
-          xstrlcpy(buf + off, p, SPACE_FOR_DIR - off + 1);
-          xfree(p);
+        if ((size_t)(buf_p - buf) < SPACE_FOR_DIR) {
+          char *const tbuf = transstr(buf_p);
+          const size_t free_space = SPACE_FOR_DIR - (size_t)(buf_p - buf) + 1;
+          const size_t dir_len = xstrlcpy(buf_p, tbuf, free_space);
+          buf_p += MIN(dir_len, free_space - 1);
+          xfree(tbuf);
         } else {
-          xstrlcpy(buf + off, "...", SPACE_FOR_ARGNR - off + 1);
+          const size_t free_space = SPACE_FOR_ARGNR - (size_t)(buf_p - buf) + 1;
+          const size_t dots_len = xstrlcpy(buf_p, "...", free_space);
+          buf_p += MIN(dots_len, free_space - 1);
         }
-        strcat(buf, ")");
+        *buf_p++ = ')';
+        *buf_p = NUL;
+      } else {
+        *buf_p = NUL;
       }
 
-      append_arg_number(curwin, (char_u *)buf, SPACE_FOR_ARGNR, false);
+      append_arg_number(curwin, (char_u *)buf_p,
+                        (int)(SPACE_FOR_ARGNR - (size_t)(buf_p - buf)), false);
 
-      strcat(buf, " - NVIM");
+      strcat(buf_p, " - NVIM");
 
       if (maxlen > 0) {
         // Make it shorter by removing a bit in the middle.

src/nvim/charset.c

@@ -359,9 +359,9 @@ size_t transstr_len(const char *const s)
 /// @param[in]  len  Buffer length. Resulting string may not occupy more then
 ///                  len - 1 bytes (one for trailing NUL byte).
 ///
-/// @return `buf` argument unchanged.
-char *transstr_buf(const char *const s, char *const buf, const size_t len)
-  FUNC_ATTR_NONNULL_RET FUNC_ATTR_NONNULL_ALL
+/// @return length of the resulting string, without the NUL byte.
+size_t transstr_buf(const char *const s, char *const buf, const size_t len)
+  FUNC_ATTR_NONNULL_ALL
 {
   const char *p = s;
   char *buf_p = buf;
@@ -400,7 +400,7 @@ char *transstr_buf(const char *const s, char *const buf, const size_t len)
   }
   *buf_p = NUL;
   assert(buf_p <= buf_e);
-  return buf;
+  return (size_t)(buf_p - buf);
 }
 
 /// Copy string and replace special characters with printable characters
@@ -416,7 +416,9 @@ char *transstr(const char *const s)
   // Compute the length of the result, taking account of unprintable
   // multi-byte characters.
   const size_t len = transstr_len((const char *)s) + 1;
-  return transstr_buf(s, xmalloc(len), len);
+  char *const buf = xmalloc(len);
+  transstr_buf(s, buf, len);
+  return buf;
 }
 
 /// Convert the string "str[orglen]" to do ignore-case comparing.

src/nvim/strings.h

@@ -3,10 +3,28 @@
 
 #include <stdbool.h>
 #include <stdarg.h>
+#include <string.h>
 
 #include "nvim/types.h"
 #include "nvim/eval/typval.h"
 
+/// Append string to string and return pointer to the next byte
+///
+/// Unlike strcat, this one does *not* add NUL byte and returns pointer to the
+/// past of the added string.
+///
+/// @param[out]  dst  String to append to.
+/// @param[in]  src  String to append.
+///
+/// @return pointer to the byte just past the appended byte.
+static inline char *strappend(char *const dst, const char *const src)
+  FUNC_ATTR_ALWAYS_INLINE FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
+  FUNC_ATTR_NONNULL_RET
+{
+  const size_t src_len = strlen(src);
+  return (char *)memmove(dst, src, src_len) + src_len;
+}
+
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "strings.h.generated.h"
 #endif