v.in.dwg: Avoid using same variable as parameter and destination in s…

…printf (#4262)

v.in.dwg: Avoid using same variable as parameter and dest in sprintf

Currently, one instance of sprintf has the same variable as parameter
and destination in sprintf. This scenario leads to undefined
behavior in C.

Modify the code to:

1. Write initial error string using snprintf() onto the buffer.
   Using snprintf() makes sure that we stay within the buffer size
   and avoid overflow errors.

2. Use snprintf() again to write another error string at the end
   of previous error string in the same buffer. We again use
   snprintf() to make sure we are not overflowing the buffer with
   data.

Signed-off-by: Mohan Yelugoti <ymdatta.work@gmail.com>

vector/v.in.dwg/main.c

@@ -66,7 +66,8 @@ int main(int argc, char *argv[])
     struct GModule *module;
     struct Option *out_opt, *in_opt;
     struct Flag *z_flag, *circle_flag, *l_flag, *int_flag;
-    char buf[2000];
+    const size_t BUFSIZE = 2000;
+    char buf[BUFSIZE];
 
     /* DWG */
     char path[2000];
@@ -135,10 +136,13 @@ int main(int argc, char *argv[])
     /* Init OpenDWG */
     sprintf(path, "%s/etc/adinit.dat", G_gisbase());
     if (!adInitAd2(path, &initerror)) {
-        sprintf(buf, _("Unable to initialize OpenDWG Toolkit, error: %d: %s."),
-                initerror, adErrorStr(initerror));
+        snprintf(buf, BUFSIZE,
+                 _("Unable to initialize OpenDWG Toolkit, error: %d: %s."),
+                 initerror, adErrorStr(initerror));
+        size_t buflen = strlen(buf);
         if (initerror == AD_UNABLE_TO_OPEN_INIT_FILE)
-            sprintf(buf, _("%s Cannot open %s"), buf, path);
+            snprintf(buf + buflen, BUFSIZE - buflen, _(" Cannot open %s"),
+                     path);
         G_fatal_error(buf);
     }
     adSetupDwgRead();