Fix a bunch of compiler warnings, particularly for old compilers

Works now much better with old C99 and C++98 standard compilers.
Fixed: C++ comments in C files and headers included by C files.

There are still some warnings with C90 though but these would be
hard to fix and left as-is for now.

test/fractals.cxx: some arrays were too small by 1, or the compiler
  warned at least (false positive?). Anyway, it's fixed now.

6 files changed, 20 insertions, 20 deletions

diff --git a/FL/fl_attr.h b/FL/fl_attr.h
index 66e59c681..52b350754 100644
--- a/FL/fl_attr.h
+++ b/FL/fl_attr.h
@@ -146,7 +146,7 @@
 
 // -- nothing yet --
 
-#endif // __clang__
+#endif /* __clang__ */
 
 
 /*
@@ -162,19 +162,19 @@
 #define __fl_attr(x) __attribute__ (x)
 #endif
 
-#if FL_GCC_VERSION > 40500 // gcc 4.5.0
+#if FL_GCC_VERSION > 40500 /* gcc 4.5.0 */
 #ifndef FL_DEPRECATED
 #define FL_DEPRECATED(msg, func) func __attribute__((deprecated(msg)))
 #endif
-#endif // gcc 4.5.0
+#endif /* gcc 4.5.0 */
 
-#if FL_GCC_VERSION > 30100 // gcc 3.1.0
+#if FL_GCC_VERSION > 30100 /* gcc 3.1.0 */
 #ifndef FL_DEPRECATED
 #define FL_DEPRECATED(msg, func) func __attribute__((deprecated))
 #endif
-#endif // gcc 3.1.0
+#endif /* gcc 3.1.0 */
 
-#endif // __GNUC__
+#endif /* __GNUC__ */
 
 
 /*
diff --git a/FL/platform_types.h b/FL/platform_types.h
index 71c412abb..c6c00974b 100644
--- a/FL/platform_types.h
+++ b/FL/platform_types.h
@@ -138,7 +138,7 @@ extern FL_EXPORT int fl_control_modifier();
 
 #endif /* FL_PLATFORM_TYPES_H */
 
-// This is currently the same for all platforms, but may change in the future
+/* This is currently the same for all platforms but may change in the future */
 struct Fl_Timestamp_t {
   time_t sec;
   int usec;
diff --git a/src/flstring.h b/src/flstring.h
index e4c7ea491..04199d13e 100644
--- a/src/flstring.h
+++ b/src/flstring.h
@@ -82,8 +82,8 @@ FL_EXPORT extern size_t fl_strlcat(char *, const char *, size_t);
 #    define strlcat fl_strlcat
 #  endif /* !HAVE_STRLCAT */
 
-// promoted to <FL/fl_string_functions.h>
-//FL_EXPORT extern size_t fl_strlcpy(char *, const char *, size_t);
+/* promoted to <FL/fl_string_functions.h> */
+/* FL_EXPORT extern size_t fl_strlcpy(char *, const char *, size_t); */
 #  ifndef HAVE_STRLCPY
 #    define strlcpy fl_strlcpy
 #  endif /* !HAVE_STRLCPY */
diff --git a/src/numericsort.c b/src/numericsort.c
index bf73bb927..244f0334d 100644
--- a/src/numericsort.c
+++ b/src/numericsort.c
@@ -73,7 +73,6 @@ static int numericsort(struct dirent **A, struct dirent **B, int cs) {
       }
 
       if (a >= end_a) break;
-      //a++; b++;
     }
   }
   if (!ret) return 0;
diff --git a/src/xutf8/utf8Wrap.c b/src/xutf8/utf8Wrap.c
index 5ca8f25d4..4a2b45bb6 100644
--- a/src/xutf8/utf8Wrap.c
+++ b/src/xutf8/utf8Wrap.c
@@ -37,7 +37,7 @@
  */
 
 /* The ARM header files have a bug by not taking into account that ARM cpu
- * likes packing to 4 bytes. This little trick defines our own version of
+ * likes padding to 4 bytes. This little trick defines our own version of
  * XChar2b which does not have this problem
  */
 
diff --git a/test/fractals.cxx b/test/fractals.cxx
index b680d3d0d..bbdde0569 100644
--- a/test/fractals.cxx
+++ b/test/fractals.cxx
@@ -5,7 +5,7 @@
 // demonstrate how to add FLTK controls to a GLUT program.   The GLUT
 // code is unchanged except for the end (search for FLTK to find changes).
 //
-// Copyright 1998-2016 by Bill Spitzak and others.
+// Copyright 1998-2024 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -77,6 +77,7 @@ typedef enum { NOTALLOWED, MOUNTAIN, TREE, ISLAND, BIGMTN, STEM, LEAF,
                MOUNTAIN_MAT, WATER_MAT, LEAF_MAT, TREE_MAT, STEMANDLEAVES,
                AXES } DisplayLists;
 
+// Note: MAXLEVEL is the highest level, range is 0..MAXLEVEL
 #define MAXLEVEL 8
 
 int Rebuild = 1,        /* Rebuild display list in next display? */
@@ -146,11 +147,11 @@ float xzslope(float v1[3], float v2[3])
 /************************ MOUNTAIN STUFF ***********************/
 /***************************************************************/
 
-GLfloat DispFactor[MAXLEVEL];  /* Array of what to multiply random number
-                                  by for a given level to get midpoint
-                                  displacement  */
-GLfloat DispBias[MAXLEVEL];  /* Array of what to add to random number
-                                before multiplying it by DispFactor */
+GLfloat DispFactor[MAXLEVEL + 1]; /* Array of what to multiply random number
+                                     by for a given level to get midpoint
+                                     displacement  */
+GLfloat DispBias[MAXLEVEL + 1];   /* Array of what to add to random number
+                                     before multiplying it by DispFactor */
 
 #define NUMRANDS 191
 float RandTable[NUMRANDS];  /* hash table of random numbers so we can
@@ -233,9 +234,9 @@ void FMR(GLfloat v1[3], GLfloat v2[3], GLfloat v3[3], int level)
 void FractalMountain(GLfloat v1[3], GLfloat v2[3], GLfloat v3[3],
                      int pegged[3])
 {
-  GLfloat lengths[MAXLEVEL];
-  GLfloat fraction[8] = { 0.3f, 0.3f, 0.4f, 0.2f, 0.3f, 0.2f, 0.4f, 0.4f  };
-  GLfloat bias[8]     = { 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f  };
+  GLfloat lengths[MAXLEVEL + 1];
+  GLfloat fraction[8] = { 0.3f, 0.3f, 0.4f, 0.2f, 0.3f, 0.2f, 0.4f, 0.4f };
+  GLfloat bias[8]     = { 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f, 0.1f };
   int i;
   float avglen = (xzlength(v1, v2) +
                   xzlength(v2, v3) +