From ea6155677e0f466d05a0027fdbe29827f4a08c2c Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 2 Jun 2021 14:09:18 -0400
Subject: Enable -Wimplicit-fallthrough

---
 Makefile |  9 ++++++++-
 parse.c  | 10 +++++-----
 printf.c |  2 +-
 util.h   | 14 ++++++++++++++
 4 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/Makefile b/Makefile
index 994962f..5d70c6e 100644
--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,14 @@ INSTALL ?= install
 MKDIR ?= mkdir -p
 RM ?= rm -f
 
-DEFAULT_CFLAGS ?= -g -Wall -Wmissing-declarations -Wshadow -Wsign-compare -Wstrict-prototypes
+DEFAULT_CFLAGS := \
+    -g \
+    -Wall \
+    -Wmissing-declarations \
+    -Wshadow \
+    -Wsign-compare \
+    -Wstrict-prototypes \
+    -Wimplicit-fallthrough
 
 CFLAGS ?= $(DEFAULT_CFLAGS)
 LDFLAGS ?=
diff --git a/parse.c b/parse.c
index 2475290..6ad580b 100644
--- a/parse.c
+++ b/parse.c
@@ -1800,7 +1800,7 @@ static int parse_mode(const struct parser_state *state, const char *mode, struct
 		case MODE_CLAUSE:
 			who = 0;
 			mstate = MODE_WHO;
-			// Fallthrough
+			fallthrough;
 
 		case MODE_WHO:
 			switch (*i) {
@@ -1827,7 +1827,7 @@ static int parse_mode(const struct parser_state *state, const char *mode, struct
 			case MODE_EQUALS:
 				expr->file_mode &= ~who;
 				expr->dir_mode &= ~who;
-				// Fallthrough
+				fallthrough;
 			case MODE_PLUS:
 				expr->file_mode |= file_change;
 				expr->dir_mode |= dir_change;
@@ -1837,7 +1837,7 @@ static int parse_mode(const struct parser_state *state, const char *mode, struct
 				expr->dir_mode &= ~dir_change;
 				break;
 			}
-			// Fallthrough
+			fallthrough;
 
 		case MODE_ACTION:
 			if (who == 0) {
@@ -1919,7 +1919,7 @@ static int parse_mode(const struct parser_state *state, const char *mode, struct
 				break;
 			case 'x':
 				file_change |= who & 0111;
-				// Fallthrough
+				fallthrough;
 			case 'X':
 				dir_change |= who & 0111;
 				break;
@@ -1982,7 +1982,7 @@ static struct expr *parse_perm(struct parser_state *state, int field, int arg2)
 			++mode;
 			break;
 		}
-		// Fallthrough
+		fallthrough;
 	default:
 		expr->mode_cmp = MODE_EXACT;
 		break;
diff --git a/printf.c b/printf.c
index 4a2c65a..26c19a7 100644
--- a/printf.c
+++ b/printf.c
@@ -630,7 +630,7 @@ struct bfs_printf *bfs_printf_parse(const struct bfs_ctx *ctx, const char *forma
 				case '0':
 				case '+':
 					must_be_numeric = true;
-					// Fallthrough
+					fallthrough;
 				case ' ':
 				case '-':
 					if (strchr(directive->str, c)) {
diff --git a/util.h b/util.h
index 1b52513..7b8b877 100644
--- a/util.h
+++ b/util.h
@@ -42,6 +42,12 @@
 #	define BFS_HAS_INCLUDE(header, fallback) fallback
 #endif
 
+#ifdef __has_c_attribute
+#	define BFS_HAS_C_ATTRIBUTE(attr) __has_c_attribute(attr)
+#else
+#	define BFS_HAS_C_ATTRIBUTE(attr) false
+#endif
+
 #ifndef BFS_HAS_MNTENT
 #	define BFS_HAS_MNTENT BFS_HAS_INCLUDE(<mntent.h>, __GLIBC__)
 #endif
@@ -86,6 +92,14 @@
 #	define O_DIRECTORY 0
 #endif
 
+#if BFS_HAS_C_ATTRIBUTE(fallthrough)
+#	define fallthrough [[fallthrough]]
+#elif __GNUC__
+#	define fallthrough __attribute__((fallthrough))
+#else
+#	define fallthrough
+#endif
+
 /**
  * Adds compiler warnings for bad printf()-style function calls, if supported.
  */
-- 
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