Add additional warning flags and PNGLIB_FALLTHROUGH

CMakeLists.txt

@@ -30,6 +30,10 @@ project(libpng
         VERSION ${PNGLIB_VERSION}
         LANGUAGES C ASM)
 
+if(CMAKE_C_COMPILER_ID STREQUAL "Clang")
+set(CMAKE_C_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra -Wimplicit-fallthrough -Waddress -Wenum-compare -Winfinite-recursion -Wmisleading-indentation -Wself-assign -Wshift-sign-overflow -Wuninitialized -Wunused -Werror")
+endif()
+
 if(POLICY CMP0074)
   # Allow find_package() to use the ZLIB_ROOT variable, if available.
   cmake_policy(SET CMP0074 NEW)

contrib/libtests/pngstest.c

@@ -14,6 +14,8 @@
 #define _ISOC90_SOURCE 1
 #define MALLOC_CHECK_ 2 /*glibc facility: turn on debugging*/
 
+#include "pngpriv.h"
+
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
@@ -2888,13 +2890,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
                {
                   case 4:
                      if (pua[btoa[3]] != pub[3]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 3:
                      if (pua[btoa[2]] != pub[2]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 2:
                      if (pua[btoa[1]] != pub[1]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 1:
                      if (pua[btoa[0]] != pub[0]) break;
                      if (alpha_added != 4 && pub[alpha_added] != 65535) break;
@@ -2910,13 +2912,13 @@ compare_two_images(Image *a, Image *b, int via_linear,
                {
                   case 4:
                      if (psa[btoa[3]] != psb[3]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 3:
                      if (psa[btoa[2]] != psb[2]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 2:
                      if (psa[btoa[1]] != psb[1]) break;
-                     /* FALLTHROUGH */
+                     PNGLIB_FALLTHROUGH;
                   case 1:
                      if (psa[btoa[0]] != psb[0]) break;
                      if (alpha_added != 4 && psb[alpha_added] != 255) break;

contrib/libtests/pngunknown.c

@@ -16,6 +16,8 @@
  *   currently just a minimal validation for the built-in libpng facilities.
  */
 
+#include "pngpriv.h"
+
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
@@ -103,6 +105,7 @@ typedef png_byte *png_const_bytep;
 #define PNG_u2(b1, b2) (((unsigned int)(b1) << 8) + (b2))
 
 #define PNG_U16(b1, b2) ((png_uint_16)PNG_u2(b1, b2))
+#undef PNG_U32
 #define PNG_U32(b1, b2, b3, b4)\
    (((png_uint_32)PNG_u2(b1, b2) << 16) + PNG_u2(b3, b4))
 
@@ -627,7 +630,7 @@ get_unknown(display *d, png_infop info_ptr, int after_IDAT)
                   ++(d->error_count);
                   break;
                }
-               /* FALLTHROUGH */ /* (safe) */
+               PNGLIB_FALLTHROUGH; /* (safe) */
             case PNG_HANDLE_CHUNK_ALWAYS:
                break;
          }

contrib/libtests/pngvalid.c

@@ -24,6 +24,8 @@
 #define _BSD_SOURCE 1 /* For the floating point exception extension */
 #define _DEFAULT_SOURCE 1 /* For the floating point exception extension */
 
+#include "pngpriv.h"
+
 #include <signal.h>
 #include <stdio.h>
 
@@ -6595,16 +6597,16 @@ 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 */
+      PNGLIB_FALLTHROUGH;
    case PNG_COLOR_TYPE_GRAY:
       if (dp->output_bit_depth == 1 || dp->output_bit_depth == 2 ||
          dp->output_bit_depth == 4)
          break;
-      /* FALLTHROUGH */
+      PNGLIB_FALLTHROUGH;
    default:
       if (dp->output_bit_depth == 8 || dp->output_bit_depth == 16)
          break;
-      /* FALLTHROUGH */
+      // Fall through to error (not a case so no PNGLIB_FALLTHROUGH)
    error:
       {
          char message[128];
@@ -10007,7 +10009,7 @@ gamma_component_validate(const char *name, const validate_info *vi,
                   use_background = (alpha >= 0 && alpha < 1);
 #           endif
 #           ifdef PNG_READ_ALPHA_MODE_SUPPORTED
-               /* FALLTHROUGH */
+               PNGLIB_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

@@ -10,6 +10,8 @@
  * See the usage message for more information.
  */
 
+#include "pngpriv.h"
+
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
@@ -2405,7 +2407,7 @@ zlib_advance(struct zlib *zlib, png_uint_32 nbytes)
                   endrc = ZLIB_TOO_FAR_BACK;
                   break;
                }
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
 
             default:
                zlib_message(zlib, 0/*stream error*/);
@@ -2559,7 +2561,7 @@ zlib_run(struct zlib *zlib)
                   list->lengths[i] -= zlib->extra_bytes;
                   list->count = i+1;
                   zlib->idat->idat_list_tail = list;
-                  /* FALLTHROUGH */
+                  PNGLIB_FALLTHROUGH;
 
                default:
                   return rc;
@@ -2662,7 +2664,7 @@ 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 */
+            PNGLIB_FALLTHROUGH;
 
          default:
             /* Unrecoverable error; skip the chunk; a zlib_message has already
@@ -3330,7 +3332,7 @@ read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
                if (file->state != STATE_IDAT && length > 0)
                   setpos(chunk);
             }
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
 
          default:
             assert(chunk != NULL);

pngerror.c

@@ -163,7 +163,7 @@ png_format_number(png_const_charp start, png_charp end, int format,
          case PNG_NUMBER_FORMAT_02u:
             /* Expects at least 2 digits. */
             mincount = 2;
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
 
          case PNG_NUMBER_FORMAT_u:
             *--end = digits[number % 10];
@@ -173,7 +173,7 @@ png_format_number(png_const_charp start, png_charp end, int format,
          case PNG_NUMBER_FORMAT_02x:
             /* This format expects at least two digits */
             mincount = 2;
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
 
          case PNG_NUMBER_FORMAT_x:
             *--end = digits[number & 0xf];

pngpriv.h

@@ -2170,6 +2170,15 @@ PNG_INTERNAL_FUNCTION(int,
 
 /* Maintainer: Put new private prototypes here ^ */
 
+#if defined(__has_attribute)
+#  if __has_attribute(fallthrough)
+#    define PNGLIB_FALLTHROUGH __attribute__((fallthrough))
+#  endif
+#endif
+#if !defined(PNGLIB_FALLTHROUGH)
+#  define PNGLIB_FALLTHROUGH (void)0
+#endif
+
 #include "pngdebug.h"
 
 #ifdef __cplusplus

pngread.c

@@ -1906,7 +1906,7 @@ png_create_colormap_entry(png_image_read_control *display,
          {
             case 4:
                entry[afirst ? 0 : 3] = (png_uint_16)alpha;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
 
             case 3:
                if (alpha < 65535)
@@ -1928,7 +1928,7 @@ png_create_colormap_entry(png_image_read_control *display,
 
             case 2:
                entry[1 ^ afirst] = (png_uint_16)alpha;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
 
             case 1:
                if (alpha < 65535)
@@ -1957,7 +1957,7 @@ png_create_colormap_entry(png_image_read_control *display,
          {
             case 4:
                entry[afirst ? 0 : 3] = (png_byte)alpha;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
             case 3:
                entry[afirst + (2 ^ bgr)] = (png_byte)blue;
                entry[afirst + 1] = (png_byte)green;
@@ -1966,7 +1966,7 @@ png_create_colormap_entry(png_image_read_control *display,
 
             case 2:
                entry[1 ^ afirst] = (png_byte)alpha;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
             case 1:
                entry[afirst] = (png_byte)green;
                break;
@@ -2886,7 +2886,7 @@ png_image_read_colormap(png_voidp argument)
       case P_sRGB:
          /* Change to 8-bit sRGB */
          png_set_alpha_mode_fixed(png_ptr, PNG_ALPHA_PNG, PNG_GAMMA_sRGB);
-         /* FALLTHROUGH */
+         PNGLIB_FALLTHROUGH;
 
       case P_FILE:
          if (png_ptr->bit_depth > 8)

pngrtran.c

@@ -60,7 +60,7 @@ png_set_crc_action(png_structrp png_ptr, int crit_action, int ancil_action)
       case PNG_CRC_WARN_DISCARD:    /* Not a valid action for critical data */
          png_warning(png_ptr,
              "Can't discard critical data on CRC error");
-         /* FALLTHROUGH */
+         PNGLIB_FALLTHROUGH;
       case PNG_CRC_ERROR_QUIT:                                /* Error/quit */
 
       case PNG_CRC_DEFAULT:
@@ -1263,7 +1263,7 @@ png_init_rgb_transformations(png_structrp png_ptr)
             default:
 
             case 8:
-               /* FALLTHROUGH */ /*  (Already 8 bits) */
+               PNGLIB_FALLTHROUGH; /*  (Already 8 bits) */
 
             case 16:
                /* Already a full 16 bits */

pngrutil.c

@@ -3071,7 +3071,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
          case 2:
             png_ptr->user_chunk_cache_max = 1;
             png_chunk_benign_error(png_ptr, "no space in chunk cache");
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
          case 1:
             /* NOTE: prior to 1.6.0 this case resulted in an unknown critical
              * chunk being skipped, now there will be a hard error below.
@@ -3080,7 +3080,7 @@ png_handle_unknown(png_structrp png_ptr, png_inforp info_ptr,
 
          default: /* not at limit */
             --(png_ptr->user_chunk_cache_max);
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
          case 0: /* no limit */
 #  endif /* USER_LIMITS */
             /* Here when the limit isn't reached or when limits are compiled

pngwrite.c

@@ -1034,7 +1034,7 @@ png_set_filter(png_structrp png_ptr, int method, int filters)
          case 6:
          case 7: png_app_error(png_ptr, "Unknown row filter for method 0");
 #endif /* WRITE_FILTER */
-            /* FALLTHROUGH */
+            PNGLIB_FALLTHROUGH;
          case PNG_FILTER_VALUE_NONE:
             png_ptr->do_filter = PNG_FILTER_NONE; break;
 
@@ -1909,7 +1909,7 @@ png_image_set_PLTE(png_image_write_control *display)
                tRNS[i] = entry[afirst ? 0 : 3];
                if (tRNS[i] < 255)
                   num_trans = i+1;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
             case 3:
                palette[i].blue = entry[afirst + (2 ^ bgr)];
                palette[i].green = entry[afirst + 1];
@@ -1920,7 +1920,7 @@ png_image_set_PLTE(png_image_write_control *display)
                tRNS[i] = entry[1 ^ afirst];
                if (tRNS[i] < 255)
                   num_trans = i+1;
-               /* FALLTHROUGH */
+               PNGLIB_FALLTHROUGH;
             case 1:
                palette[i].blue = palette[i].red = palette[i].green =
                   entry[afirst];