[libpng18] [code standardisation] Use standard C attributes

contrib/libtests/pngstest.c

@@ -1,7 +1,7 @@
 /* pngstest.c
  *
  * Copyright (c) 2021-2024 Cosmin Truta
- * Copyright (c) 2013-2017 John Cunningham Bowler
+ * Copyright (c) 2013-2017,2024 John Cunningham Bowler
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -46,6 +46,18 @@
 #ifdef PNG_SIMPLIFIED_READ_SUPPORTED /* Else nothing can be done */
 #include "../tools/sRGB.h"
 
+/* This is a sanity check on PNG_HAS_ATTRIBUTE.
+ */
+#if PNG_HAS_ATTRIBUTE(__unknown__::attribute)
+#  error PNG_HAS_ATTRIBUTE is not working correctly
+#endif
+
+#if PNG_HAS_ATTRIBUTE(fallthrough)
+#  define FALLTHROUGH PNG_ATTRIBUTE(fallthrough)
+#else
+#  define FALLTRHOUGH /* FALLTHROUGH */
+#endif
+
 /* KNOWN ISSUES
  *
  * These defines switch on alternate algorithms for format conversions to match
@@ -2885,13 +2897,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
                {
                   case 4:
                      if (pua[btoa[3]] != pub[3]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 3:
                      if (pua[btoa[2]] != pub[2]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 2:
                      if (pua[btoa[1]] != pub[1]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 1:
                      if (pua[btoa[0]] != pub[0]) break;
                      if (alpha_added != 4 && pub[alpha_added] != 65535) break;
@@ -2907,13 +2919,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
                {
                   case 4:
                      if (psa[btoa[3]] != psb[3]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 3:
                      if (psa[btoa[2]] != psb[2]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 2:
                      if (psa[btoa[1]] != psb[1]) break;
-                     /* FALLTHROUGH */
+                     FALLTHROUGH; /* FALLTHROUGH */
                   case 1:
                      if (psa[btoa[0]] != psb[0]) break;
                      if (alpha_added != 4 && psb[alpha_added] != 255) break;

contrib/libtests/pngunknown.c

@@ -2,6 +2,7 @@
  *
  * Copyright (c) 2021-2024 Cosmin Truta
  * Copyright (c) 2015,2017 Glenn Randers-Pehrson
+ * Copyright (c) 2015-2016,2024 John Bowler
  * Written by John Cunningham Bowler
  *
  * This code is released under the libpng license.
@@ -38,6 +39,12 @@
 #  define SKIP 0
 #endif
 
+#if PNG_HAS_ATTRIBUTE(fallthrough)
+#  define FALLTHROUGH PNG_ATTRIBUTE(fallthrough)
+#else
+#  define FALLTRHOUGH /* FALLTHROUGH */
+#endif
+
 
 /* Since this program tests the ability to change the unknown chunk handling
  * these must be defined:
@@ -433,7 +440,7 @@ clean_display(display *d)
    }
 }
 
-PNG_FUNCTION(void, display_exit, (display *d), static PNG_NORETURN)
+PNG_FUNCTION(void, display_exit, (display *d), PNG_NORETURN static)
 {
    ++(d->error_count);
 
@@ -457,7 +464,7 @@ display_rc(const display *d, int strict)
 
 /* libpng error and warning callbacks */
 PNG_FUNCTION(void, (PNGCBAPI error), (png_structp png_ptr, const char *message),
-   static PNG_NORETURN)
+   PNG_NORETURN static)
 {
    display *d = (display*)png_get_error_ptr(png_ptr);
 
@@ -623,7 +630,7 @@ get_unknown(display *d, png_infop info_ptr, int after_IDAT)
                   ++(d->error_count);
                   break;
                }
-               /* FALLTHROUGH */ /* (safe) */
+               FALLTHROUGH; /* (safe) */ /* FALLTHROUGH */
             case PNG_HANDLE_CHUNK_ALWAYS:
                break;
          }
@@ -1104,7 +1111,7 @@ static const char *standard_tests[] =
    NULL /*end*/
 };
 
-static PNG_NORETURN void
+PNG_NORETURN static void
 usage(const char *program, const char *reason)
 {
    fprintf(stderr, "pngunknown: %s: usage:\n %s [--strict] "

contrib/libtests/pngvalid.c

@@ -1,7 +1,7 @@
 /* pngvalid.c - validate libpng by constructing then reading png files.
  *
  * Copyright (c) 2021-2024 Cosmin Truta
- * Copyright (c) 2014-2017 John Cunningham Bowler
+ * Copyright (c) 2014-2017,2024 John Cunningham Bowler
  *
  * This code is released under the libpng license.
  * For conditions of distribution and use, see the disclaimer
@@ -156,6 +156,13 @@ typedef png_byte *png_const_bytep;
 #  endif
 #endif
 
+#if PNG_HAS_ATTRIBUTE(fallthrough)
+#  define FALLTHROUGH PNG_ATTRIBUTE(fallthrough)
+#else
+#  define FALLTRHOUGH /* FALLTHROUGH */
+#endif
+
+
 /***************************** EXCEPTION HANDLING *****************************/
 #ifdef PNG_FREESTANDING_TESTS
 #  include <cexcept.h>
@@ -6589,12 +6596,12 @@ transform_info_imp(transform_display *dp, png_structp pp, png_infop pi)
    {
    case PNG_COLOR_TYPE_PALETTE:
       if (dp->output_bit_depth > 8) goto error;
-      /* FALLTHROUGH */
+      FALLTHROUGH; /* FALLTHROUGH */
    case PNG_COLOR_TYPE_GRAY:
       if (dp->output_bit_depth == 1 || dp->output_bit_depth == 2 ||
          dp->output_bit_depth == 4)
          break;
-      /* FALLTHROUGH */
+      FALLTHROUGH; /* FALLTHROUGH */
    default:
       if (dp->output_bit_depth == 8 || dp->output_bit_depth == 16)
          break;
@@ -10001,7 +10008,7 @@ gamma_component_validate(const char *name, const validate_info *vi,
                   use_background = (alpha >= 0 && alpha < 1);
 #           endif
 #           ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-               /* FALLTHROUGH */
+                  FALLTHROUGH; /* FALLTHROUGH */
                case ALPHA_MODE_OFFSET + PNG_ALPHA_STANDARD:
                case ALPHA_MODE_OFFSET + PNG_ALPHA_BROKEN:
                case ALPHA_MODE_OFFSET + PNG_ALPHA_OPTIMIZED:

contrib/tools/pngfix.c

@@ -31,6 +31,12 @@
 #  include "../../png.h"
 #endif
 
+#if PNG_HAS_ATTRIBUTE(fallthrough)
+#  define FALLTHROUGH PNG_ATTRIBUTE(fallthrough)
+#else
+#  define FALLTRHOUGH /* FALLTHROUGH */
+#endif
+
 #ifdef PNG_SETJMP_SUPPORTED
 #include <setjmp.h>
 
@@ -2399,7 +2405,7 @@ zlib_advance(struct zlib *zlib, png_uint_32 nbytes)
                   endrc = ZLIB_TOO_FAR_BACK;
                   break;
                }
-               /* FALLTHROUGH */
+               FALLTHROUGH; /* FALLTHROUGH */
 
             default:
                zlib_message(zlib, 0/*stream error*/);
@@ -2553,7 +2559,7 @@ zlib_run(struct zlib *zlib)
                   list->lengths[i] -= zlib->extra_bytes;
                   list->count = i+1;
                   zlib->idat->idat_list_tail = list;
-                  /* FALLTHROUGH */
+                  FALLTHROUGH; /* FALLTHROUGH */
 
                default:
                   return rc;
@@ -2656,7 +2662,7 @@ zlib_check(struct file *file, png_uint_32 offset)
             /* Truncated stream; unrecoverable, gets converted to ZLIB_FATAL */
             zlib.z.msg = PNGZ_MSG_CAST("[truncated]");
             zlib_message(&zlib, 0/*expected*/);
-            /* FALLTHROUGH */
+            FALLTHROUGH; /* FALLTHROUGH */
 
          default:
             /* Unrecoverable error; skip the chunk; a zlib_message has already
@@ -3324,7 +3330,7 @@ read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
                if (file->state != STATE_IDAT && length > 0)
                   setpos(chunk);
             }
-            /* FALLTHROUGH */
+            FALLTHROUGH; /* FALLTHROUGH */
 
          default:
             assert(chunk != NULL);