pvs-studio: (V1086) Fix buffer writes

Replace space-filling memset calls with bounded character initialization that
preserves null termination for the curses help text buffers.

.pvsconfig

@@ -88,8 +88,6 @@
 //-V::1071
 # Conditional initialization inside the constructor may leave some members uninitialized.
 //-V::1077
-# Call of the 'Foo' function will lead to buffer underflow.
-//-V::1086
 # Waiting on condition variable without predicate. A thread can wait indefinitely or experience a spurious wake-up.
 //-V::1089
 # The 'emplace' / 'insert' function call contains potentially dangerous move operation. Moved object can be destroyed even if there is no insertion.

Source/CursesDialog/cmCursesMainForm.cxx

@@ -314,9 +314,12 @@ void cmCursesMainForm::PrintKeys(int process /* = 0 */)
     char secondLine[512] = "";
     char thirdLine[512] = "";
     if (process) {
-      memset(firstLine, ' ', 68);
-      memset(secondLine, ' ', 68);
-      memset(thirdLine, ' ', 68);
+      std::fill_n(firstLine, 68, ' ');
+      firstLine[68] = '\0';
+      std::fill_n(secondLine, 68, ' ');
+      secondLine[68] = '\0';
+      std::fill_n(thirdLine, 68, ' ');
+      thirdLine[68] = '\0';
     } else {
       if (this->OkToGenerate) {
         snprintf(firstLine, sizeof(firstLine),
@@ -340,7 +343,8 @@ void cmCursesMainForm::PrintKeys(int process /* = 0 */)
     move(y - 4, 0);
     char fmt[512] = "Keys: [enter] Edit an entry [d] Delete an entry";
     if (process) {
-      memset(fmt, ' ', 57);
+      std::fill_n(fmt, 57, ' ');
+      fmt[57] = '\0';
     }
     printw(fmt_s, fmt);
     move(y - 3, 0);

Tests/CMakeLib/testUVStreambuf.cxx

@@ -246,7 +246,8 @@ static bool testUVStreambufRead(
               << std::endl;
     goto end;
   }
-  if (std::memcmp(inputData.data(), outputData, 64)) {
+  if (std::memcmp(inputData.data(), outputData, //-V1086 Ignore underflow
+                  64)) {
     std::cout << "Read data does not match write data" << std::endl;
     goto end;
   }