Change pqformat.h's integer handling functions to take unsigned integers.

As added in 1de09ad8 the new functions
all accept signed integers as parameters. That's not great, because
it's perfectly reasonable to call them with unsigned parameters.
Unfortunately unsigned to signed conversion is not well defined, when
exceeding the range of the signed value.  That's presently not a
practical issue in postgres (among other reasons because we force
gcc's hand with -fwrapv).  But it's clearly not quite right.

Thus change the signatures to accept unsigned integers instead, signed
to unsigned conversion is always well defined. Also change the
backward compat pq_sendint() - while it's deprecated it seems better
to be consistent.

Per discussion between Andrew Gierth, Michael Paquier, Alvaro Herrera
and Tom Lane.

Reported-By: Andrew Gierth
Author: Andres Freund
Discussion: https://postgr.es/m/87r2m10zm2.fsf@news-spur.riddles.org.uk

src/include/libpq/pqformat.h

@@ -35,7 +35,7 @@ extern void pq_sendfloat4(StringInfo buf, float4 f);
 extern void pq_sendfloat8(StringInfo buf, float8 f);
 
 /*
- * Append an int8 to a StringInfo buffer, which already has enough space
+ * Append a [u]int8 to a StringInfo buffer, which already has enough space
  * preallocated.
  *
  * The use of pg_restrict allows the compiler to optimize the code based on
@@ -47,55 +47,55 @@ extern void pq_sendfloat8(StringInfo buf, float8 f);
  * overly picky and demanding a * before a restrict.
  */
 static inline void
-pq_writeint8(StringInfoData *pg_restrict buf, int8 i)
+pq_writeint8(StringInfoData *pg_restrict buf, uint8 i)
 {
-	int8		ni = i;
+	uint8		ni = i;
 
-	Assert(buf->len + (int) sizeof(int8) <= buf->maxlen);
-	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(int8));
-	buf->len += sizeof(int8);
+	Assert(buf->len + (int) sizeof(uint8) <= buf->maxlen);
+	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint8));
+	buf->len += sizeof(uint8);
 }
 
 /*
- * Append an int16 to a StringInfo buffer, which already has enough space
+ * Append a [u]int16 to a StringInfo buffer, which already has enough space
  * preallocated.
  */
 static inline void
-pq_writeint16(StringInfoData *pg_restrict buf, int16 i)
+pq_writeint16(StringInfoData *pg_restrict buf, uint16 i)
 {
-	int16		ni = pg_hton16(i);
+	uint16		ni = pg_hton16(i);
 
-	Assert(buf->len + (int) sizeof(int16) <= buf->maxlen);
-	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(int16));
-	buf->len += sizeof(int16);
+	Assert(buf->len + (int) sizeof(uint16) <= buf->maxlen);
+	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint16));
+	buf->len += sizeof(uint16);
 }
 
 /*
- * Append an int32 to a StringInfo buffer, which already has enough space
+ * Append a [u]int32 to a StringInfo buffer, which already has enough space
  * preallocated.
  */
 static inline void
-pq_writeint32(StringInfoData *pg_restrict buf, int32 i)
+pq_writeint32(StringInfoData *pg_restrict buf, uint32 i)
 {
-	int32		ni = pg_hton32(i);
+	uint32		ni = pg_hton32(i);
 
-	Assert(buf->len + (int) sizeof(int32) <= buf->maxlen);
-	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(int32));
-	buf->len += sizeof(int32);
+	Assert(buf->len + (int) sizeof(uint32) <= buf->maxlen);
+	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint32));
+	buf->len += sizeof(uint32);
 }
 
 /*
- * Append an int64 to a StringInfo buffer, which already has enough space
+ * Append a [u]int64 to a StringInfo buffer, which already has enough space
  * preallocated.
  */
 static inline void
-pq_writeint64(StringInfoData *pg_restrict buf, int64 i)
+pq_writeint64(StringInfoData *pg_restrict buf, uint64 i)
 {
-	int64		ni = pg_hton64(i);
+	uint64		ni = pg_hton64(i);
 
-	Assert(buf->len + (int) sizeof(int64) <= buf->maxlen);
-	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(int64));
-	buf->len += sizeof(int64);
+	Assert(buf->len + (int) sizeof(uint64) <= buf->maxlen);
+	memcpy((char *pg_restrict) (buf->data + buf->len), &ni, sizeof(uint64));
+	buf->len += sizeof(uint64);
 }
 
 /*
@@ -127,41 +127,41 @@ pq_writestring(StringInfoData *pg_restrict buf, const char *pg_restrict str)
 		pfree(p);
 }
 
-/* append a binary int8 to a StringInfo buffer */
+/* append a binary [u]int8 to a StringInfo buffer */
 static inline void
-pq_sendint8(StringInfo buf, int8 i)
+pq_sendint8(StringInfo buf, uint8 i)
 {
-	enlargeStringInfo(buf, sizeof(int8));
+	enlargeStringInfo(buf, sizeof(uint8));
 	pq_writeint8(buf, i);
 }
 
-/* append a binary int16 to a StringInfo buffer */
+/* append a binary [u]int16 to a StringInfo buffer */
 static inline void
-pq_sendint16(StringInfo buf, int16 i)
+pq_sendint16(StringInfo buf, uint16 i)
 {
-	enlargeStringInfo(buf, sizeof(int16));
+	enlargeStringInfo(buf, sizeof(uint16));
 	pq_writeint16(buf, i);
 }
 
-/* append a binary int32 to a StringInfo buffer */
+/* append a binary [u]int32 to a StringInfo buffer */
 static inline void
-pq_sendint32(StringInfo buf, int32 i)
+pq_sendint32(StringInfo buf, uint32 i)
 {
-	enlargeStringInfo(buf, sizeof(int32));
+	enlargeStringInfo(buf, sizeof(uint32));
 	pq_writeint32(buf, i);
 }
 
-/* append a binary int64 to a StringInfo buffer */
+/* append a binary [u]int64 to a StringInfo buffer */
 static inline void
-pq_sendint64(StringInfo buf, int64 i)
+pq_sendint64(StringInfo buf, uint64 i)
 {
-	enlargeStringInfo(buf, sizeof(int64));
+	enlargeStringInfo(buf, sizeof(uint64));
 	pq_writeint64(buf, i);
 }
 
 /* append a binary byte to a StringInfo buffer */
 static inline void
-pq_sendbyte(StringInfo buf, int8 byt)
+pq_sendbyte(StringInfo buf, uint8 byt)
 {
 	pq_sendint8(buf, byt);
 }
@@ -172,18 +172,18 @@ pq_sendbyte(StringInfo buf, int8 byt)
  * This function is deprecated; prefer use of the functions above.
  */
 static inline void
-pq_sendint(StringInfo buf, int i, int b)
+pq_sendint(StringInfo buf, uint32 i, int b)
 {
 	switch (b)
 	{
 		case 1:
-			pq_sendint8(buf, (int8) i);
+			pq_sendint8(buf, (uint8) i);
 			break;
 		case 2:
-			pq_sendint16(buf, (int16) i);
+			pq_sendint16(buf, (uint16) i);
 			break;
 		case 4:
-			pq_sendint32(buf, (int32) i);
+			pq_sendint32(buf, (uint32) i);
 			break;
 		default:
 			elog(ERROR, "unsupported integer size %d", b);