Fix the new ARMv8 CRC code for short and unaligned input.

hlinnaka · hlinnaka · commit 3a5e0a91bb32 · 2018-04-04T14:40:39.000+03:00
The code before the main loop, to handle the possible 1-7 unaligned bytes
at the beginning of the input, was broken, and read past the input, if the
the input was very short.
diff --git a/src/port/pg_crc32c_armv8.c b/src/port/pg_crc32c_armv8.c
@@ -29,17 +29,17 @@ pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len)
 	 * significantly faster. Process leading bytes so that the loop below
 	 * starts with a pointer aligned to eight bytes.
 	 */
-	if (!PointerIsAligned(p, uint16) && p < pend)
+	if (!PointerIsAligned(p, uint16) && p + 1 <= pend)
 	{
 		crc = __crc32cb(crc, *p);
 		p += 1;
 	}
-	if (!PointerIsAligned(p, uint32) && p < pend)
+	if (!PointerIsAligned(p, uint32) && p + 2 <= pend)
 	{
 		crc = __crc32ch(crc, *(uint16 *) p);
 		p += 2;
 	}
-	if (!PointerIsAligned(p, uint64) && p < pend)
+	if (!PointerIsAligned(p, uint64) && p + 4 <= pend)
 	{
 		crc = __crc32cw(crc, *(uint32 *) p);
 		p += 4;

Original file line number	Diff line number	Diff line change
`@@ -29,17 +29,17 @@ pg_comp_crc32c_armv8(pg_crc32c crc, const void *data, size_t len)`
`29`	`29`	`* significantly faster. Process leading bytes so that the loop below`
`30`	`30`	`* starts with a pointer aligned to eight bytes.`
`31`	`31`	`*/`
`32`		`- if (!PointerIsAligned(p, uint16) && p < pend)`
	`32`	`+ if (!PointerIsAligned(p, uint16) && p + 1 <= pend)`
`33`	`33`	`{`
`34`	`34`	`crc = __crc32cb(crc, *p);`
`35`	`35`	`p += 1;`
`36`	`36`	`}`
`37`		`- if (!PointerIsAligned(p, uint32) && p < pend)`
	`37`	`+ if (!PointerIsAligned(p, uint32) && p + 2 <= pend)`
`38`	`38`	`{`
`39`	`39`	`crc = __crc32ch(crc, (uint16 ) p);`
`40`	`40`	`p += 2;`
`41`	`41`	`}`
`42`		`- if (!PointerIsAligned(p, uint64) && p < pend)`
	`42`	`+ if (!PointerIsAligned(p, uint64) && p + 4 <= pend)`
`43`	`43`	`{`
`44`	`44`	`crc = __crc32cw(crc, (uint32 ) p);`
`45`	`45`	`p += 4;`