Fix a few more warnings by Clang.

- Apple Clang 17.0.0.
- png, z, jpeg lib integer cast warnings remain
- FLTK callback function cast warnings remain.

src/Fl_Help_View.cxx

@@ -886,7 +886,7 @@ int Fl_Help_View::Impl::do_align(
 void Fl_Help_View::Impl::format() {
   int           i;              // Looping var
   int           done;           // Are we done yet?
-  Text_Block *block,         // Current block
+  Text_Block    *block = nullptr, // Current block
                 *cell;          // Current table cell
   int           cells[MAX_COLUMNS],
                                 // Cells in the current row...
@@ -899,7 +899,7 @@ void Fl_Help_View::Impl::format() {
                 wattr[1024],    // Width attribute buffer
                 hattr[1024],    // Height attribute buffer
                 linkdest[1024]; // Link destination
-  int           xx, yy, ww, hh; // Size of current text fragment
+  int           xx, yy, ww, hh = 0; // Size of current text fragment
   int           line;           // Current line in block
   int           links;          // Links for current line
   Fl_Font       font;

src/Fl_Menu.cxx

@@ -423,12 +423,12 @@ int Menu_Window::display_height_ = 0;
  */
 Menu_Window::Menu_Window(const Fl_Menu_Item* m, int X, int Y, int Wp, int Hp,
                          const Fl_Menu_Item* picked, const Fl_Menu_Item* t,
-                         int menubar, int menubar_title, int right_edge)
+                         int menubar, int mb_title, int right_edge)
 : Menu_Window_Basetype(X, Y, Wp, Hp, m)
 {
   int scr_x, scr_y, scr_w, scr_h;
   int tx = X, ty = Y;
-  menubar_title = menubar_title;
+  menubar_title = mb_title;
   int n = (Wp > 0 ? Fl::screen_num(X, Y) : -1);
   Fl_Window_Driver::driver(this)->menu_window_area(scr_x, scr_y, scr_w, scr_h, n);
   if (!right_edge || right_edge > scr_x+scr_w)

src/Fl_XPM_Image.cxx

@@ -59,7 +59,9 @@ Fl_XPM_Image::Fl_XPM_Image(const char *name) : Fl_Pixmap((char *const*)0) {
   int malloc_size = INITIALLINES;
   char buffer[MAXSIZE+20];
   int i = 0;
-  int W,H,ncolors,chars_per_pixel;
+  int W = 0, H = 0;
+  int ncolors = 0;
+  int chars_per_pixel = 0;
   while (fgets(buffer,MAXSIZE+20,f)) {
     if (buffer[0] != '\"') continue;
     char *myp = buffer;

src/fl_draw.cxx

@@ -201,7 +201,7 @@ void fl_draw(
   char *linebuf = NULL;       // Pointer to a buffer managed by expand_text_
   const char* p;              // Scratch pointer into text, multiple use
   const char* e;              // Scratch pointer into text, multiple use
-  int buflen;                 // Number of bytes copied into linebuf
+  int buflen = 0;             // Number of bytes copied into linebuf
                               // by expand_text_
   char symbol[2][255];        // Copy of symbol text at start and end of str
   int symwidth[2];            // Width and height of symbols (always square)
@@ -211,7 +211,7 @@ void fl_draw(
   int imgvert = ((align&FL_ALIGN_IMAGE_NEXT_TO_TEXT)==0); // True if image is
                               // above or below text
   int lines;                  // Number of text lines including '\n' and wrapping
-  double width;               // width of the longest text line
+  double width = 0.0;         // width of the longest text line
   int height = fl_height();   // Height of a line of text
 
 

test/threads.cxx

@@ -97,7 +97,7 @@ extern "C" void* prime_func(void* p) {
   // initialize alternate buffers (struct prime) to store primes
 
   struct prime pr[2];
-  pr[0].idx       = pr[1].idx       = n/2 - 1;
+  pr[0].idx       = pr[1].idx       = ((int)n/2 - 1);
   pr[0].done      = 0;
   pr[1].done      = 1;
   pr[0].terminal  = pr[1].terminal  = terminal;