PoC: precompute string lengths

Author: egmontkob

src/subshell/common.c

@@ -1403,6 +1403,11 @@ create_cd_command (const char *s)
         escape_fmt = "\\0%03o";
     }
 
+    const int quote_cmd_start_len = strlen (quote_cmd_start);
+    const int before_wrap_len = strlen (before_wrap);
+    const int after_wrap_len = strlen (after_wrap);
+    const int quote_cmd_end_len = strlen (quote_cmd_end);
+
     /* Measure the length of an escaped byte. In the unlikely case that it won't be uniform in some
      * future shell, have an upper estimate by measuring the largest byte. */
     const int escaped_char_len = sprintf (buf, escape_fmt, 0xFF);
@@ -1414,13 +1419,12 @@ create_cd_command (const char *s)
         g_string_append (ret, "./");
 
     // Copy the beginning of the command to the buffer
-    g_string_append (ret, quote_cmd_start);
+    g_string_append_len (ret, quote_cmd_start, quote_cmd_start_len);
 
     /* Sending physical lines over a certain small limit causes problems on some platforms,
      * see ticket #4480. Make sure to wrap in time. See how large we can grow so that an
      * additional line wrapping or closing string still fits. */
-    const int max_length =
-        COOKED_MODE_BUFFER_SIZE - MAX (strlen (before_wrap), strlen (quote_cmd_end));
+    const int max_length = COOKED_MODE_BUFFER_SIZE - MAX (before_wrap_len, quote_cmd_end_len);
     g_assert (max_length >= 64);  // Make sure we have enough room to breathe.
 
     line_length = ret->len;
@@ -1436,10 +1440,10 @@ create_cd_command (const char *s)
             if (line_length + (n - su) > max_length)
             {
                 // wrap to next physical line
-                g_string_append (ret, before_wrap);
+                g_string_append_len (ret, before_wrap, before_wrap_len);
                 g_string_append_c (ret, '\n');
-                g_string_append (ret, after_wrap);
-                line_length = strlen (after_wrap);
+                g_string_append_len (ret, after_wrap, after_wrap_len);
+                line_length = after_wrap_len;
             }
             // append character
             g_string_append_len (ret, su, (size_t) (n - su));
@@ -1451,18 +1455,18 @@ create_cd_command (const char *s)
                 if (line_length + escaped_char_len > max_length)
                 {
                     // wrap to next physical line
-                    g_string_append (ret, before_wrap);
+                    g_string_append_len (ret, before_wrap, before_wrap_len);
                     g_string_append_c (ret, '\n');
-                    g_string_append (ret, after_wrap);
-                    line_length = strlen (after_wrap);
+                    g_string_append_len (ret, after_wrap, after_wrap_len);
+                    line_length = after_wrap_len;
                 }
                 // append escaped byte
                 g_string_append_printf (ret, escape_fmt, (unsigned char) su[c]);
                 line_length += escaped_char_len;
             }
     }
 
-    g_string_append (ret, quote_cmd_end);
+    g_string_append_len (ret, quote_cmd_end, quote_cmd_end_len);
 
     return ret;
 }