Revert "Clean up implicit fall through."

This reverts commit 6a703f5b0edfdbf2eee72d59499f73585262a46f.

Reason for revert: This change breaks building coreboot

Original change's description:
> Clean up implicit fall through.
> 
> Directly use the __attribute__ ((fallthrough)) instead of
> a macro.
> This was suggested in CL:1772474.
> 
> BUG=chromium:997709
> TEST=CQ
> BRANCH=None
> 
> Change-Id: Ic6cd417d7c735395a4b136dbb0879a6f1716da98
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1897360
> Tested-by: Manoj Gupta <manojgupta@chromium.org>
> Reviewed-by: Julius Werner <jwerner@chromium.org>
> Commit-Queue: Manoj Gupta <manojgupta@chromium.org>

Bug: chromium:997709
Change-Id: Icd0de8bcdee44d1b41f313a4f5aaba8108f734ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/1899735
Reviewed-by: Mathew King <mathewk@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Commit-Queue: Julius Werner <jwerner@chromium.org>
Tested-by: Julius Werner <jwerner@chromium.org>

6 files changed, 28 insertions, 7 deletions

diff --git a/firmware/2lib/include/2common.h b/firmware/2lib/include/2common.h
index b4e941c5..6c5563a6 100644
--- a/firmware/2lib/include/2common.h
+++ b/firmware/2lib/include/2common.h
@@ -71,6 +71,27 @@ struct vb2_public_key;
 #endif
 #endif
 
+// Have a generic fall-through for different versions of C/C++.
+// Taken from boringssl.
+#if defined(__cplusplus) && __cplusplus >= 201703L
+#define VBOOT_FALLTHROUGH [[fallthrough]]
+#elif defined(__cplusplus) && __cplusplus >= 201103L && defined(__clang__)
+#define VBOOT_FALLTHROUGH [[clang::fallthrough]]
+#elif defined(__cplusplus) && __cplusplus >= 201103L && defined(__GNUC__) && \
+    __GNUC__ >= 7
+#define VBOOT_FALLTHROUGH [[gnu::fallthrough]]
+#elif defined(__GNUC__) && __GNUC__ >= 7 // gcc 7
+#define VBOOT_FALLTHROUGH __attribute__ ((fallthrough))
+#elif defined(__clang__)
+#if __has_attribute(fallthrough)
+#define VBOOT_FALLTHROUGH __attribute__ ((fallthrough))
+#else // clang versions that do not support fallthrough.
+#define VBOOT_FALLTHROUGH
+#endif
+#else // C++11 on gcc 6, and all other cases
+#define VBOOT_FALLTHROUGH
+#endif
+
 /**
  * Round up a number to a multiple of VB2_WORKBUF_ALIGN
  *
diff --git a/firmware/lib/cgptlib/cgptlib.c b/firmware/lib/cgptlib/cgptlib.c
index db704b54..7803a7e9 100644
--- a/firmware/lib/cgptlib/cgptlib.c
+++ b/firmware/lib/cgptlib/cgptlib.c
@@ -143,8 +143,8 @@ int GptUpdateKernelWithEntry(GptData *gpt, GptEntry *e, uint32_t update_type)
 			break;
 		}
 		/* Out of tries, so drop through and mark partition bad. */
-		__attribute__ ((fallthrough));
 	}
+	VBOOT_FALLTHROUGH;
 	case GPT_UPDATE_ENTRY_BAD: {
 		/* Giving up on this partition entirely. */
 		if (!GetEntrySuccessful(e)) {
diff --git a/firmware/lib/vboot_ui.c b/firmware/lib/vboot_ui.c
index ac509430..c8ef8cdc 100644
--- a/firmware/lib/vboot_ui.c
+++ b/firmware/lib/vboot_ui.c
@@ -258,7 +258,7 @@ static vb2_error_t vb2_enter_vendor_data_ui(struct vb2_context *ctx,
 			return VB2_SUCCESS;
 		case 'a'...'z':
 			key = toupper(key);
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		case '0'...'9':
 		case 'A'...'Z':
 			if ((len > 0 && is_vowel(key)) ||
@@ -594,7 +594,7 @@ static vb2_error_t vb2_developer_ui(struct vb2_context *ctx)
 			/* Only disable virtual dev switch if allowed by GBB */
 			if (!(gbb->flags & VB2_GBB_FLAG_ENTER_TRIGGERS_TONORM))
 				break;
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		case ' ':
 			/* See if we should disable virtual dev-mode switch. */
 			VB2_DEBUG("shared->flags=%#x\n", shared->flags);
diff --git a/futility/cmd_dump_fmap.c b/futility/cmd_dump_fmap.c
index 48f9185c..ef46ffcd 100644
--- a/futility/cmd_dump_fmap.c
+++ b/futility/cmd_dump_fmap.c
@@ -444,7 +444,7 @@ static int do_dump_fmap(int argc, char *argv[])
 			break;
 		case 'H':
 			opt_gaps = 1;
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		case 'h':
 			opt_format = FMT_HUMAN;
 			opt_overlap++;
@@ -507,7 +507,7 @@ static int do_dump_fmap(int argc, char *argv[])
 		case FMT_NORMAL:
 			printf("hit at 0x%08x\n",
 			       (uint32_t) ((char *)fmap - (char *)base_of_rom));
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		default:
 			retval = normal_fmap(fmap,
 					     argc - optind - 1,
diff --git a/futility/cmd_sign.c b/futility/cmd_sign.c
index 9bfba4f8..fb096763 100644
--- a/futility/cmd_sign.c
+++ b/futility/cmd_sign.c
@@ -721,7 +721,7 @@ static int do_sign(int argc, char *argv[])
 			break;
 		case OPT_FV:
 			sign_option.fv_specified = 1;
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		case OPT_INFILE:
 			sign_option.inout_file_count++;
 			infile = optarg;
diff --git a/host/lib/crossystem.c b/host/lib/crossystem.c
index 1bad2cfb..3a418939 100644
--- a/host/lib/crossystem.c
+++ b/host/lib/crossystem.c
@@ -409,7 +409,7 @@ static int GetVdatInt(VdatIntField field)
 			break;
 		case VDAT_INT_FW_BOOT2:
 			value = (sh->flags & VBSD_BOOT_FIRMWARE_VBOOT2 ? 1 : 0);
-			__attribute__ ((fallthrough));
+			VBOOT_FALLTHROUGH;
 		default:
 			break;
 	}