build: Test building with clang 22.1, fix warnings uncovered (#5067)

Signed-off-by: Larry Gritz <lg@larrygritz.com>

Author: lgritz

INSTALL.md

@@ -17,7 +17,7 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
  * C++17 or higher (also builds with C++20 and C++23)
      * The default build mode is C++17. This can be controlled by via the
        CMake configuration flag: `-DCMAKE_CXX_STANDARD=20`, etc.
- * Compilers: gcc 9.3 - 14.2, clang 10 - 20, MSVS 2017 - 2022 (v19.14
+ * Compilers: gcc 9.3 - 14.2, clang 10 - 22, MSVS 2017 - 2022 (v19.14
    and up), Intel OneAPI C++ compiler 2022+.
  * CMake >= 3.18.2 (tested through 4.1)
  * Imath >= 3.1 (tested through 3.2 and main)

src/iv/imageviewer.cpp

@@ -1743,7 +1743,7 @@ DateTime_to_time_t(string_view datetime, time_t& timet)
         return false;
     // print("{}:{}:{} {}:{}:{}\n", year, month, day, hour, min, sec);
     struct tm tmtime;
-    time_t now;
+    time_t now = time(nullptr);
     Sysutil::get_local_time(&now, &tmtime);  // fill in defaults
     tmtime.tm_sec  = sec;
     tmtime.tm_min  = min;