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Adjust comments about avoiding use of printf's %.*s.

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My initial impression that glibc was measuring the precision in characters
(which is what the Linux man page says it does) was incorrect.  It does take
the precision to be in bytes, but it also tries to truncate the string at a
character boundary.  The bottom line remains the same: it will mess up
if the string is not in the encoding it expects, so we need to avoid %.*s
anytime there's a significant risk of that.  Previous code changes are still
good, but adjust the comments to reflect this knowledge.  Per research by
Hernan Gonzalez.
This commit is contained in:
Tom Lane
2010-05-09 02:16:00 +00:00
parent 54cd4f0457
commit ed437e2b27
6 changed files with 21 additions and 26 deletions
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6
src/bin/psql/print.c
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@ -3,7 +3,7 @@
*
* Copyright (c) 2000-2010, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/bin/psql/print.c,v 1.125 2010/05/08 16:39:52 tgl Exp $
* $PostgreSQL: pgsql/src/bin/psql/print.c,v 1.126 2010/05/09 02:15:59 tgl Exp $
*/
#include "postgres_fe.h"
@ -255,8 +255,8 @@ format_numeric_locale(const char *my_str)
/*
* 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.
* 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)