Work around a subtle portability problem in use of printf %s format.

Depending on which spec you read, field widths and precisions in %s may be
counted either in bytes or characters.  Our code was assuming bytes, which
is wrong at least for glibc's implementation, and in any case libc might
have a different idea of the prevailing encoding than we do.  Hence, for
portable results we must avoid using anything more complex than just "%s"
unless the string to be printed is known to be all-ASCII.

This patch fixes the cases I could find, including the psql formatting
failure reported by Hernan Gonzalez.  In HEAD only, I also added comments
to some places where it appears safe to continue using "%.*s".

1 files changed, 25 insertions, 4 deletions

diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index cd9f56fe38b..fff8b6e3881 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -23,7 +23,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-misc.c,v 1.122.2.1 2005/11/22 18:23:30 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-misc.c,v 1.122.2.2 2010/05/08 16:40:38 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -70,6 +70,20 @@ static int	pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time);
 
 
 /*
+ * fputnbytes: print exactly N bytes to a file
+ *
+ * Think not to use fprintf with a %.*s format for this.  Some machines
+ * believe %s's precision is measured in characters, others in bytes.
+ */
+static void
+fputnbytes(FILE *f, const char *str, size_t n)
+{
+	while (n-- > 0)
+		fputc(*str++, f);
+}
+
+
+/*
  * pqGetc: get 1 character from the connection
  *
  *	All these routines return 0 on success, EOF on error.
@@ -175,8 +189,11 @@ pqGetnchar(char *s, size_t len, PGconn *conn)
 	conn->inCursor += len;
 
 	if (conn->Pfdebug)
-		fprintf(conn->Pfdebug, "From backend (%lu)> %.*s\n",
-				(unsigned long) len, (int) len, s);
+	{
+		fprintf(conn->Pfdebug, "From backend (%lu)> ", (unsigned long) len);
+		fputnbytes(conn->Pfdebug, s, len);
+		fprintf(conn->Pfdebug, "\n");
+	}
 
 	return 0;
 }
@@ -192,7 +209,11 @@ pqPutnchar(const char *s, size_t len, PGconn *conn)
 		return EOF;
 
 	if (conn->Pfdebug)
-		fprintf(conn->Pfdebug, "To backend> %.*s\n", (int) len, s);
+	{
+		fprintf(conn->Pfdebug, "To backend> ");
+		fputnbytes(conn->Pfdebug, s, len);
+		fprintf(conn->Pfdebug, "\n");
+	}
 
 	return 0;
 }