From 248e8530dd0298e9bbe099c651d5d9c4d2a0c0f9 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Thu, 18 Jul 2024 11:34:09 -0700
Subject: [PATCH] libbacktrace: use __has_attribute for fallthrough

Also convert some FALLTHROUGH comments to ATTRIBUTE_FALLTHROUGH.

	* internal.h: Use __has_attribute to check for fallthrough
	attribute.
	* elf.c (elf_zstd_decompress): Use ATTRIBUTE_FALLTHROUGH rather
	than a FALLTHROUGH comment.
---
 libbacktrace/elf.c      | 14 +++++++-------
 libbacktrace/internal.h |  5 +++++
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/libbacktrace/elf.c b/libbacktrace/elf.c
index e8d67feab6d..0040479143d 100644
--- a/libbacktrace/elf.c
+++ b/libbacktrace/elf.c
@@ -4848,25 +4848,25 @@ elf_zstd_decompress (const unsigned char *pin, size_t sin,
 		  {
 		  case 8:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 7:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 6:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 5:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 4:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 3:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 2:
 		    *pout++ = *plit++;
-		    /* FALLTHROUGH */
+		    ATTRIBUTE_FALLTHROUGH;
 		  case 1:
 		    *pout++ = *plit++;
 		    break;
diff --git a/libbacktrace/internal.h b/libbacktrace/internal.h
index a119cda692f..fe2abe50b0f 100644
--- a/libbacktrace/internal.h
+++ b/libbacktrace/internal.h
@@ -56,6 +56,11 @@ POSSIBILITY OF SUCH DAMAGE.  */
 # endif
 #endif
 
+#ifdef __has_attribute
+# if __has_attribute(fallthrough)
+#  define ATTRIBUTE_FALLTHROUGH __attribute__ ((fallthrough))
+# endif
+#endif
 #ifndef ATTRIBUTE_FALLTHROUGH
 # if (GCC_VERSION >= 7000)
 #  define ATTRIBUTE_FALLTHROUGH __attribute__ ((__fallthrough__))