Use __attribute__((fallthrough)) rather than magic GCC comments.

GCC added an implicit-fallthrough warning a while back, where it
would complain if you had a nontrivial "case:" block that didn't end
with break, return, or something like that.  Clang recently added
the same thing.

GCC, however, would let you annotate a fall-through as intended by
any of various magic "/* fall through */" comments.  Clang, however,
only seems to like "__attribute__((fallthrough))".  Fortunately, GCC
accepts that too.

A previous commit in this branch defined a FALLTHROUGH macro to do
the right thing if GNUC is defined; here we replace all of our "fall
through" comments with uses of that macro.

This is an automated commit, made with the following perl one-liner:

  #!/usr/bin/perl -i -p
  s#/\* *falls? ?thr.*?\*/#FALLTHROUGH;#i;

3 files changed, 43 insertions, 43 deletions

diff --git a/src/ext/csiphash.c b/src/ext/csiphash.c
index a6a9846db4..a65b6fcbe6 100644
--- a/src/ext/csiphash.c
+++ b/src/ext/csiphash.c
@@ -88,13 +88,13 @@ uint64_t siphash24(const void *src, unsigned long src_sz, const struct sipkey *k
 	}
 
 	switch (src_sz - blocks) {
-		case 7: last7 |= (uint64_t)m[i + 6] << 48; /* Falls through. */
-		case 6: last7 |= (uint64_t)m[i + 5] << 40; /* Falls through. */
-		case 5:	last7 |= (uint64_t)m[i + 4] << 32; /* Falls through. */
-		case 4: last7 |= (uint64_t)m[i + 3] << 24; /* Falls through. */
-		case 3:	last7 |= (uint64_t)m[i + 2] << 16; /* Falls through. */
-		case 2:	last7 |= (uint64_t)m[i + 1] <<  8; /* Falls through. */
-		case 1: last7 |= (uint64_t)m[i + 0]      ; /* Falls through. */
+		case 7: last7 |= (uint64_t)m[i + 6] << 48; FALLTHROUGH;
+		case 6: last7 |= (uint64_t)m[i + 5] << 40; FALLTHROUGH;
+		case 5:	last7 |= (uint64_t)m[i + 4] << 32; FALLTHROUGH;
+		case 4: last7 |= (uint64_t)m[i + 3] << 24; FALLTHROUGH;
+		case 3:	last7 |= (uint64_t)m[i + 2] << 16; FALLTHROUGH;
+		case 2:	last7 |= (uint64_t)m[i + 1] <<  8; FALLTHROUGH;
+		case 1: last7 |= (uint64_t)m[i + 0]      ; FALLTHROUGH;
 		case 0:
 		default:;
 	}
diff --git a/src/ext/ed25519/donna/modm-donna-32bit.h b/src/ext/ed25519/donna/modm-donna-32bit.h
index 0ef9e58fa1..5934d9ca9d 100644
--- a/src/ext/ed25519/donna/modm-donna-32bit.h
+++ b/src/ext/ed25519/donna/modm-donna-32bit.h
@@ -385,14 +385,14 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 	size_t i = 0;
 	bignum256modm_element_t carry = 0;
 	switch (limbsize) {
-		case 8: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 7: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 6: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 5: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 4: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 2: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
-		case 1: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; /* Falls through. */
+		case 8: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 7: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 6: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 5: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 4: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 2: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
+		case 1: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 31); out[i] &= 0x3fffffff; i++; FALLTHROUGH;
 		case 0: 
 		default: out[i] = (a[i] - b[i]) - carry;
 	}
@@ -403,14 +403,14 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 static int
 lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize) {
 	switch (limbsize) {
-		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; /* Falls through. */
-		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; /* Falls through. */
-		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; /* Falls through. */
-		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; /* Falls through. */
-		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; /* Falls through. */
-		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; /* Falls through. */
-		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; /* Falls through. */
-		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; /* Falls through. */
+		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; FALLTHROUGH;
+		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; FALLTHROUGH;
+		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; FALLTHROUGH;
+		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; FALLTHROUGH;
+		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; FALLTHROUGH;
+		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; FALLTHROUGH;
+		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; FALLTHROUGH;
+		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; FALLTHROUGH;
 		case 0: if (a[0] > b[0]) return 0; if (a[0] < b[0]) return 1;
 	}
 	return 0;
@@ -420,14 +420,14 @@ lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 static int
 lte256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize) {
 	switch (limbsize) {
-		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; /* Falls through. */
-		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; /* Falls through. */
-		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; /* Falls through. */
-		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; /* Falls through. */
-		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; /* Falls through. */
-		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; /* Falls through. */
-		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; /* Falls through. */
-		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; /* Falls through. */
+		case 8: if (a[8] > b[8]) return 0; if (a[8] < b[8]) return 1; FALLTHROUGH;
+		case 7: if (a[7] > b[7]) return 0; if (a[7] < b[7]) return 1; FALLTHROUGH;
+		case 6: if (a[6] > b[6]) return 0; if (a[6] < b[6]) return 1; FALLTHROUGH;
+		case 5: if (a[5] > b[5]) return 0; if (a[5] < b[5]) return 1; FALLTHROUGH;
+		case 4: if (a[4] > b[4]) return 0; if (a[4] < b[4]) return 1; FALLTHROUGH;
+		case 3: if (a[3] > b[3]) return 0; if (a[3] < b[3]) return 1; FALLTHROUGH;
+		case 2: if (a[2] > b[2]) return 0; if (a[2] < b[2]) return 1; FALLTHROUGH;
+		case 1: if (a[1] > b[1]) return 0; if (a[1] < b[1]) return 1; FALLTHROUGH;
 		case 0: if (a[0] > b[0]) return 0; if (a[0] < b[0]) return 1;
 	}
 	return 1;
diff --git a/src/ext/ed25519/donna/modm-donna-64bit.h b/src/ext/ed25519/donna/modm-donna-64bit.h
index 06c98e3039..aa361afdbc 100644
--- a/src/ext/ed25519/donna/modm-donna-64bit.h
+++ b/src/ext/ed25519/donna/modm-donna-64bit.h
@@ -294,10 +294,10 @@ sub256_modm_batch(bignum256modm out, const bignum256modm a, const bignum256modm
 	size_t i = 0;
 	bignum256modm_element_t carry = 0;
 	switch (limbsize) {
-		case 4: out[i] = (a[i] - b[i])        ; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 2:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
-		case 1:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; /* Falls through. */
+		case 4: out[i] = (a[i] - b[i])        ; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 3: out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 2:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
+		case 1:	out[i] = (a[i] - b[i]) - carry; carry = (out[i] >> 63); out[i] &= 0xffffffffffffff; i++; FALLTHROUGH;
 		case 0: 
 		default: out[i] = (a[i] - b[i]) - carry;
 	}
@@ -310,10 +310,10 @@ lt256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 	size_t i = 0;
 	bignum256modm_element_t t, carry = 0;
 	switch (limbsize) {
-		case 4: t = (a[i] - b[i])        ; carry = (t >> 63); i++; /* Falls through. */
-		case 3: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 2: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 1: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
+		case 4: t = (a[i] - b[i])        ; carry = (t >> 63); i++; FALLTHROUGH;
+		case 3: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 2: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 1: t = (a[i] - b[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
 		case 0: t = (a[i] - b[i]) - carry; carry = (t >> 63);
 	}
 	return (int)carry;
@@ -325,10 +325,10 @@ lte256_modm_batch(const bignum256modm a, const bignum256modm b, size_t limbsize)
 	size_t i = 0;
 	bignum256modm_element_t t, carry = 0;
 	switch (limbsize) {
-		case 4: t = (b[i] - a[i])        ; carry = (t >> 63); i++; /* Falls through. */
-		case 3: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 2: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
-		case 1: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; /* Falls through. */
+		case 4: t = (b[i] - a[i])        ; carry = (t >> 63); i++; FALLTHROUGH;
+		case 3: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 2: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
+		case 1: t = (b[i] - a[i]) - carry; carry = (t >> 63); i++; FALLTHROUGH;
 		case 0: t = (b[i] - a[i]) - carry; carry = (t >> 63);
 	}
 	return (int)!carry;