Mop up some no-longer-necessary hacks around printf %.*s format.

Commit 54cd4f045 added some kluges to work around an old glibc bug,
namely that %.*s could misbehave if glibc thought any characters in
the supplied string were incorrectly encoded.  Now that we use our
own snprintf.c implementation, we need not worry about that bug (even
if it still exists in the wild).  Revert a couple of particularly
ugly hacks, and remove or improve assorted comments.

Note that there can still be encoding-related hazards here: blindly
clipping at a fixed length risks producing wrongly-encoded output
if the clip splits a multibyte character.  However, code that's
doing correct multibyte-aware clipping doesn't really need a comment
about that, while code that isn't needs an explanation why not,
rather than a red-herring comment about an obsolete bug.

Discussion: https://postgr.es/m/279428.1593373684@sss.pgh.pa.us

9 files changed, 16 insertions, 75 deletions

diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index 6b1fd6d4cca..3e199bdfd0c 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -2303,11 +2303,7 @@ CopyFromErrorCallback(void *arg)
 /*
  * Make sure we don't print an unreasonable amount of COPY data in a message.
  *
- * It would seem a lot easier to just use the sprintf "precision" limit to
- * truncate the string.  However, some versions of glibc have a bug/misfeature
- * that vsnprintf will always fail (return -1) if it is asked to truncate
- * a string that contains invalid byte sequences for the current encoding.
- * So, do our own truncation.  We return a pstrdup'd copy of the input.
+ * Returns a pstrdup'd copy of the input.
  */
 static char *
 limit_printout_length(const char *str)
diff --git a/src/backend/parser/scansup.c b/src/backend/parser/scansup.c
index 18169ec4f4c..cac70d5df7a 100644
--- a/src/backend/parser/scansup.c
+++ b/src/backend/parser/scansup.c
@@ -189,20 +189,10 @@ truncate_identifier(char *ident, int len, bool warn)
 	{
 		len = pg_mbcliplen(ident, len, NAMEDATALEN - 1);
 		if (warn)
-		{
-			/*
-			 * We avoid using %.*s here because it can misbehave if the data
-			 * is not valid in what libc thinks is the prevailing encoding.
-			 */
-			char		buf[NAMEDATALEN];
-
-			memcpy(buf, ident, len);
-			buf[len] = '\0';
 			ereport(NOTICE,
 					(errcode(ERRCODE_NAME_TOO_LONG),
-					 errmsg("identifier \"%s\" will be truncated to \"%s\"",
-							ident, buf)));
-		}
+					 errmsg("identifier \"%s\" will be truncated to \"%.*s\"",
+							ident, len, ident)));
 		ident[len] = '\0';
 	}
 }
diff --git a/src/backend/tsearch/wparser_def.c b/src/backend/tsearch/wparser_def.c
index 48e55e141a4..fda35abc741 100644
--- a/src/backend/tsearch/wparser_def.c
+++ b/src/backend/tsearch/wparser_def.c
@@ -324,12 +324,6 @@ TParserInit(char *str, int len)
 	prs->state->state = TPS_Base;
 
 #ifdef WPARSER_TRACE
-
-	/*
-	 * Use of %.*s here is a bit risky since it can misbehave if the data is
-	 * not in what libc thinks is the prevailing encoding.  However, since
-	 * this is just a debugging aid, we choose to live with that.
-	 */
 	fprintf(stderr, "parsing \"%.*s\"\n", len, str);
 #endif
 
@@ -366,7 +360,6 @@ TParserCopyInit(const TParser *orig)
 	prs->state->state = TPS_Base;
 
 #ifdef WPARSER_TRACE
-	/* See note above about %.*s */
 	fprintf(stderr, "parsing copy of \"%.*s\"\n", prs->lenstr, prs->str);
 #endif
 
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 0b6dfb248cb..dec2fad82a6 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -4013,7 +4013,8 @@ EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char
 
 			/*
 			 * Note: the uses of %.*s in this function would be risky if the
-			 * timezone names ever contain non-ASCII characters.  However, all
+			 * timezone names ever contain non-ASCII characters, since we are
+			 * not being careful to do encoding-aware clipping.  However, all
 			 * TZ abbreviations in the IANA database are plain ASCII.
 			 */
 			if (print_tz)
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 076c3c019ff..2cbcb4b85e3 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -3554,11 +3554,6 @@ set_rtable_names(deparse_namespace *dpns, List *parent_namespaces,
 					hentry->counter++;
 					for (;;)
 					{
-						/*
-						 * We avoid using %.*s here because it can misbehave
-						 * if the data is not valid in what libc thinks is the
-						 * prevailing encoding.
-						 */
 						memcpy(modname, refname, refnamelen);
 						sprintf(modname + refnamelen, "_%d", hentry->counter);
 						if (strlen(modname) < NAMEDATALEN)
@@ -4438,11 +4433,6 @@ make_colname_unique(char *colname, deparse_namespace *dpns,
 			i++;
 			for (;;)
 			{
-				/*
-				 * We avoid using %.*s here because it can misbehave if the
-				 * data is not valid in what libc thinks is the prevailing
-				 * encoding.
-				 */
 				memcpy(modname, colname, colnamelen);
 				sprintf(modname + colnamelen, "_%d", i);
 				if (strlen(modname) < NAMEDATALEN)
diff --git a/src/fe_utils/print.c b/src/fe_utils/print.c
index 66a50f183f5..508f537c0c7 100644
--- a/src/fe_utils/print.c
+++ b/src/fe_utils/print.c
@@ -305,20 +305,6 @@ format_numeric_locale(const char *my_str)
 }
 
 
-/*
- * fputnbytes: print exactly N bytes to a file
- *
- * We avoid using %.*s here because it can misbehave if the data
- * is not valid in what libc thinks is the prevailing encoding.
- */
-static void
-fputnbytes(FILE *f, const char *str, size_t n)
-{
-	while (n-- > 0)
-		fputc(*str++, f);
-}
-
-
 static void
 print_separator(struct separator sep, FILE *fout)
 {
@@ -1042,16 +1028,14 @@ print_aligned_text(const printTableContent *cont, FILE *fout, bool is_pager)
 					{
 						/* spaces first */
 						fprintf(fout, "%*s", width_wrap[j] - chars_to_output, "");
-						fputnbytes(fout,
-								   (char *) (this_line->ptr + bytes_output[j]),
-								   bytes_to_output);
+						fwrite((char *) (this_line->ptr + bytes_output[j]),
+							   1, bytes_to_output, fout);
 					}
 					else		/* Left aligned cell */
 					{
 						/* spaces second */
-						fputnbytes(fout,
-								   (char *) (this_line->ptr + bytes_output[j]),
-								   bytes_to_output);
+						fwrite((char *) (this_line->ptr + bytes_output[j]),
+							   1, bytes_to_output, fout);
 					}
 
 					bytes_output[j] += bytes_to_output;
@@ -1637,8 +1621,8 @@ print_aligned_vertical(const printTableContent *cont,
 				 */
 				bytes_to_output = strlen_max_width(dlineptr[dline].ptr + offset,
 												   &target_width, encoding);
-				fputnbytes(fout, (char *) (dlineptr[dline].ptr + offset),
-						   bytes_to_output);
+				fwrite((char *) (dlineptr[dline].ptr + offset),
+					   1, bytes_to_output, fout);
 
 				chars_to_output -= target_width;
 				offset += bytes_to_output;
diff --git a/src/interfaces/ecpg/ecpglib/error.c b/src/interfaces/ecpg/ecpglib/error.c
index a4e3c0d01f8..cd6c6a6819b 100644
--- a/src/interfaces/ecpg/ecpglib/error.c
+++ b/src/interfaces/ecpg/ecpglib/error.c
@@ -270,7 +270,6 @@ ecpg_raise_backend(int line, PGresult *result, PGconn *conn, int compat)
 	else
 		sqlca->sqlcode = ECPG_PGSQL;
 
-	/* %.*s is safe here as long as sqlstate is all-ASCII */
 	ecpg_log("raising sqlstate %.*s (sqlcode %ld): %s\n",
 			 (int) sizeof(sqlca->sqlstate), sqlca->sqlstate, sqlca->sqlcode, sqlca->sqlerrm.sqlerrmc);
 
diff --git a/src/interfaces/ecpg/pgtypeslib/dt_common.c b/src/interfaces/ecpg/pgtypeslib/dt_common.c
index 81bd7aa526f..14cdf2d428b 100644
--- a/src/interfaces/ecpg/pgtypeslib/dt_common.c
+++ b/src/interfaces/ecpg/pgtypeslib/dt_common.c
@@ -826,7 +826,8 @@ EncodeDateTime(struct tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tz
 
 			/*
 			 * Note: the uses of %.*s in this function would be risky if the
-			 * timezone names ever contain non-ASCII characters.  However, all
+			 * timezone names ever contain non-ASCII characters, since we are
+			 * not being careful to do encoding-aware clipping.  However, all
 			 * TZ abbreviations in the IANA database are plain ASCII.
 			 */
 
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 9273984727a..ff840b7730d 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -68,19 +68,6 @@ PQlibVersion(void)
 	return PG_VERSION_NUM;
 }
 
-/*
- * fputnbytes: print exactly N bytes to a file
- *
- * We avoid using %.*s here because it can misbehave if the data
- * is not valid in what libc thinks is the prevailing encoding.
- */
-static void
-fputnbytes(FILE *f, const char *str, size_t n)
-{
-	while (n-- > 0)
-		fputc(*str++, f);
-}
-
 
 /*
  * pqGetc: get 1 character from the connection
@@ -204,7 +191,7 @@ pqGetnchar(char *s, size_t len, PGconn *conn)
 	if (conn->Pfdebug)
 	{
 		fprintf(conn->Pfdebug, "From backend (%lu)> ", (unsigned long) len);
-		fputnbytes(conn->Pfdebug, s, len);
+		fwrite(s, 1, len, conn->Pfdebug);
 		fprintf(conn->Pfdebug, "\n");
 	}
 
@@ -228,7 +215,7 @@ pqSkipnchar(size_t len, PGconn *conn)
 	if (conn->Pfdebug)
 	{
 		fprintf(conn->Pfdebug, "From backend (%lu)> ", (unsigned long) len);
-		fputnbytes(conn->Pfdebug, conn->inBuffer + conn->inCursor, len);
+		fwrite(conn->inBuffer + conn->inCursor, 1, len, conn->Pfdebug);
 		fprintf(conn->Pfdebug, "\n");
 	}
 
@@ -250,7 +237,7 @@ pqPutnchar(const char *s, size_t len, PGconn *conn)
 	if (conn->Pfdebug)
 	{
 		fprintf(conn->Pfdebug, "To backend> ");
-		fputnbytes(conn->Pfdebug, s, len);
+		fwrite(s, 1, len, conn->Pfdebug);
 		fprintf(conn->Pfdebug, "\n");
 	}