Disable fallthrough attribute for older GCC

Author: azuresol

core/kmod/llring.h

@@ -66,6 +66,18 @@
 #ifndef _LLRING_H_
 #define _LLRING_H_
 
+#if defined(__has_cpp_attribute)
+#if __has_cpp_attribute(fallthrough)
+#define FALLTHROUGH [[fallthrough]]
+#elif __has_cpp_attribute(clang::fallthrough)
+#define FALLTHROUGH [[clang::fallthrough]]
+#else
+#define FALLTHROUGH
+#endif
+#else
+#define FALLTHROUGH
+#endif
+
 /**
  * Note: the ring implementation is not preemptable. A producer must not
  * be interrupted by another producer that uses the same ring.
@@ -327,10 +339,10 @@ static inline int llring_set_water_mark(struct llring *r, unsigned count)
 			switch (n & 0x3) {                                     \
 			case 3:                                                \
 				r->ring[idx++] = obj_table[i++];               \
-				[[gnu::fallthrough]];                          \
+				FALLTHROUGH;                                   \
 			case 2:                                                \
 				r->ring[idx++] = obj_table[i++];               \
-				[[gnu::fallthrough]];                          \
+				FALLTHROUGH;                                   \
 			case 1:                                                \
 				r->ring[idx++] = obj_table[i++];               \
 			}                                                      \
@@ -360,10 +372,10 @@ static inline int llring_set_water_mark(struct llring *r, unsigned count)
 			switch (n & 0x3) {                                     \
 			case 3:                                                \
 				obj_table[i++] = r->ring[idx++];               \
-				[[gnu::fallthrough]];                          \
+				FALLTHROUGH;                                   \
 			case 2:                                                \
 				obj_table[i++] = r->ring[idx++];               \
-				[[gnu::fallthrough]];                          \
+				FALLTHROUGH;                                   \
 			case 1:                                                \
 				obj_table[i++] = r->ring[idx++];               \
 			}                                                      \

core/utils/copy.h

@@ -1,6 +1,18 @@
 #ifndef BESS_UTILS_COPY_H_
 #define BESS_UTILS_COPY_H_
 
+#if defined(__has_cpp_attribute)
+#if __has_cpp_attribute(fallthrough)
+#define FALLTHROUGH [[fallthrough]]
+#elif __has_cpp_attribute(clang::fallthrough)
+#define FALLTHROUGH [[clang::fallthrough]]
+#else
+#define FALLTHROUGH
+#endif
+#else
+#define FALLTHROUGH
+#endif
+
 #include <glog/logging.h>
 #include <x86intrin.h>
 
@@ -78,7 +90,7 @@ static inline void CopySmall(void *__restrict__ dst,
       break;
     case 9:
       memcpy(d + 8, s + 8, 1);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 8:
       memcpy(d, s, 8);
       break;
@@ -91,13 +103,13 @@ static inline void CopySmall(void *__restrict__ dst,
       break;
     case 5:
       memcpy(d + 4, s + 4, 1);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 4:
       memcpy(d, s, 4);
       break;
     case 3:
       memcpy(d + 2, s + 2, 1);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 2:
       memcpy(d, s, 2);
       break;
@@ -171,22 +183,22 @@ static inline void CopyInlined(void *__restrict__ dst,
   switch (leftover_blocks) {
     case 7:
       copy_block(d + 6, s + 6);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 6:
       copy_block(d + 5, s + 5);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 5:
       copy_block(d + 4, s + 4);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 4:
       copy_block(d + 3, s + 3);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 3:
       copy_block(d + 2, s + 2);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 2:
       copy_block(d + 1, s + 1);
-      [[gnu::fallthrough]];
+      FALLTHROUGH;
     case 1:
       copy_block(d + 0, s + 0);
   }