Merge branch 'wip/otte/fallthrough' into 'master'

Add G_GNUC_FALLTHROUGH for __attribute__(fallthrough))

See merge request GNOME/glib!296

docs/reference/glib/glib-sections.txt

@@ -438,6 +438,7 @@ G_GNUC_DEPRECATED_FOR
 G_GNUC_BEGIN_IGNORE_DEPRECATIONS
 G_GNUC_END_IGNORE_DEPRECATIONS
 G_GNUC_NORETURN
+G_GNUC_FALLTHROUGH
 G_GNUC_UNUSED
 G_GNUC_PRINTF
 G_GNUC_SCANF

gio/tests/data-output-stream.c

@@ -166,9 +166,11 @@ test_data_array (guchar *buffer, gsize len,
     case TEST_DATA_INT16:
     case TEST_DATA_UINT16:
       g_assert_cmpint (len % 2, ==, 0);
+      G_GNUC_FALLTHROUGH;
     case TEST_DATA_INT32:
     case TEST_DATA_UINT32:
       g_assert_cmpint (len % 4, ==, 0);
+      G_GNUC_FALLTHROUGH;
     case TEST_DATA_INT64:
     case TEST_DATA_UINT64:
       g_assert_cmpint (len % 8, ==, 0);

gio/tests/sleepy-stream.c

@@ -33,12 +33,14 @@ cook_piece (void)
         {
          case 26:
           buffer[i++] = '\n';
+          G_GNUC_FALLTHROUGH;
          case 27:
           buffer[i++] = '\r';
           break;
 
          case 28:
           buffer[i++] = '\r';
+          G_GNUC_FALLTHROUGH;
          case 29:
           buffer[i++] = '\n';
           break;

glib/docs.c

@@ -2280,6 +2280,22 @@
  * See the GNU C documentation for more details.
  */
 
+/**
+ * G_GNUC_FALLTHROUGH:
+ *
+ * Expands to the GNU C fallthrough statement attribute if the compiler is gcc.
+ * This allows declaring case statement to explicitly fall through in switch
+ * statements. To enable this feature, use -Wimplicit-fallthrough during
+ * compilation.
+ *
+ * Put the attribute right before the case statement you want to fall through
+ * to.
+ *
+ * See the GNU C documentation for more details.
+ *
+ * Since: 2.60
+ */
+
 /**
  * G_GNUC_UNUSED:
  *

glib/gbase64.c

@@ -170,8 +170,11 @@ g_base64_encode_step (const guchar *in,
       /* len can only be 0 1 or 2 */
       switch(len)
         {
-        case 2: *saveout++ = *inptr++;
-        case 1: *saveout++ = *inptr++;
+        case 2:
+          *saveout++ = *inptr++;
+          G_GNUC_FALLTHROUGH;
+        case 1:
+          *saveout++ = *inptr++;
         }
       ((char *)save)[0] += len;
     }

glib/gconvert.c

@@ -788,7 +788,8 @@ g_convert_with_fallback (const gchar *str,
 		  inbytes_remaining = strlen (p);
 		  break;
 		}
-	      /* fall thru if p is NULL */
+              /* if p is null */
+              G_GNUC_FALLTHROUGH;
 	    default:
               {
                 int errsv = errno;

glib/gmacros.h

@@ -191,6 +191,12 @@
 #define G_GNUC_NO_INSTRUMENT
 #endif  /* !__GNUC__ */
 
+#if    __GNUC__ > 6
+#define G_GNUC_FALLTHROUGH __attribute__((fallthrough))
+#else
+#define G_GNUC_FALLTHROUGH
+#endif /* __GNUC__ */
+
 #if    __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1)
 #define G_GNUC_DEPRECATED __attribute__((__deprecated__))
 #else

glib/gmarkup.c

@@ -2872,6 +2872,8 @@ failure:
             case G_MARKUP_COLLECT_STRDUP:
               if (written)
                 g_free (*(char **) ptr);
+              *(char **) ptr = NULL;
+              break;
 
             case G_MARKUP_COLLECT_STRING:
               *(char **) ptr = NULL;

glib/gregex.c

@@ -2537,6 +2537,7 @@ expand_escape (const gchar        *replacement,
           base = 8;
           p = g_utf8_next_char (p);
         }
+      G_GNUC_FALLTHROUGH;
     case '1':
     case '2':
     case '3':

glib/gtimezone.c

@@ -372,6 +372,8 @@ parse_constant_offset (const gchar *name,
           *offset = -*offset;
           return TRUE;
         }
+      else
+        return FALSE;
 
     default:
       return FALSE;

glib/gvariant-parser.c

@@ -210,10 +210,7 @@ token_stream_prepare (TokenStream *stream)
           break;
         }
 
-      else
-        {
-          /* ↓↓↓ */
-        }
+      G_GNUC_FALLTHROUGH;
 
     case 'a': /* 'b' */ case 'c': case 'd': case 'e': case 'f':
     case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
@@ -1646,6 +1643,8 @@ string_parse (TokenStream  *stream,
           case '\n': i++; continue;
           }
 
+        G_GNUC_FALLTHROUGH;
+
       default:
         str[j++] = token[i++];
       }
@@ -1773,6 +1772,8 @@ bytestring_parse (TokenStream  *stream,
           case '\n': i++; continue;
           }
 
+        G_GNUC_FALLTHROUGH;
+
       default:
         str[j++] = token[i++];
       }

meson.build

@@ -344,6 +344,7 @@ if cc.get_id() == 'gcc' or cc.get_id() == 'clang'
   test_c_args = [
     '-Wall',
     '-Wduplicated-branches',
+    '-Wimplicit-fallthrough',
     '-Wmisleading-indentation',
     '-Wstrict-prototypes',
     '-Wunused',