Revert "Reland: Clean up implicit fall through."stabilize-rust-13613.B

This reverts commit 6208b9aa9c4e8b7c9ff8063965c9f9aa519c1740.

Upstream coreboot has raised concerns that relying on GCC 7+ features
for host utilities is too restrictive, so revert this and go back to
customizing fallthrough annotations by compiler. Cleaned out some of the
C++-specific stuff because vboot isn't built with C++.

BRANCH=None
BUG=None
TEST=Built with clang and GCC.

Change-Id: I75d796d289b0a6c249fc8ac2dadb1453be468642
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2547821
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Joel Kitching <kitching@chromium.org>

7 files changed, 14 insertions, 7 deletions

diff --git a/firmware/2lib/include/2common.h b/firmware/2lib/include/2common.h
index dbc62643..0d66458f 100644
--- a/firmware/2lib/include/2common.h
+++ b/firmware/2lib/include/2common.h
@@ -84,6 +84,13 @@ struct vb2_public_key;
 #endif
 #endif
 
+#if (defined(__GNUC__) && __GNUC__ >= 7) || \
+    (defined(__clang__) && __has_attribute(fallthrough))
+#define VBOOT_FALLTHROUGH __attribute__((fallthrough))
+#else
+#define VBOOT_FALLTHROUGH ((void)0)
+#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 3fbb2fdc..4c091d04 100644
--- a/firmware/lib/cgptlib/cgptlib.c
+++ b/firmware/lib/cgptlib/cgptlib.c
@@ -142,7 +142,7 @@ 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. */
diff --git a/firmware/lib/vboot_ui_legacy_clamshell.c b/firmware/lib/vboot_ui_legacy_clamshell.c
index a1ffe5b0..027b49ea 100644
--- a/firmware/lib/vboot_ui_legacy_clamshell.c
+++ b/firmware/lib/vboot_ui_legacy_clamshell.c
@@ -295,7 +295,7 @@ 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("sd->flags=%#x\n", sd->flags);
diff --git a/firmware/lib/vboot_ui_legacy_wilco.c b/firmware/lib/vboot_ui_legacy_wilco.c
index 59a49684..7838bcfe 100644
--- a/firmware/lib/vboot_ui_legacy_wilco.c
+++ b/firmware/lib/vboot_ui_legacy_wilco.c
@@ -67,7 +67,7 @@ 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)) ||
diff --git a/futility/cmd_dump_fmap.c b/futility/cmd_dump_fmap.c
index ff7252c6..3a0e14ed 100644
--- a/futility/cmd_dump_fmap.c
+++ b/futility/cmd_dump_fmap.c
@@ -445,7 +445,7 @@ 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++;
@@ -508,7 +508,7 @@ 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 c95b8c97..6243e3a8 100644
--- a/futility/cmd_sign.c
+++ b/futility/cmd_sign.c
@@ -722,7 +722,7 @@ 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 25a55d82..bb10c399 100644
--- a/host/lib/crossystem.c
+++ b/host/lib/crossystem.c
@@ -313,7 +313,7 @@ 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;
 	}