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Re: [PATCH v4] fix warnings in sys/select.h fortification with -Wsign-conversion
On 06/09/2012 06:30 AM, Carlos O'Donell wrote:
> If nobody else objects please check this in on Monday.
I object to this change, on the same grounds that I
objected when the same change was proposed last month
by Paul Pluzhnikov: the patch may mask a later bug if
someone mistakenly invokes the macro with D being a pointer.
Paul came up with a better patch, which doesn't have this
problem, and I propose that it be installed instead.
<http://sourceware.org/ml/libc-alpha/2012-05/msg01879.html>
Here's a copy, to save you from clicking on the link.
diff --git a/debug/fdelt_chk.c b/debug/fdelt_chk.c
index 5e06f8f..ded3f2f 100644
--- a/debug/fdelt_chk.c
+++ b/debug/fdelt_chk.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2011, 2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -18,10 +18,10 @@
#include <sys/select.h>
-unsigned long int
-__fdelt_chk (unsigned long int d)
+long int
+__fdelt_chk (long int d)
{
- if (d >= FD_SETSIZE)
+ if (d < 0 || d >= FD_SETSIZE)
__chk_fail ();
return d / __NFDBITS;
diff --git a/misc/bits/select2.h b/misc/bits/select2.h
index 9679925..76ae368 100644
--- a/misc/bits/select2.h
+++ b/misc/bits/select2.h
@@ -1,5 +1,5 @@
/* Checking macros for select functions.
- Copyright (C) 2011 Free Software Foundation, Inc.
+ Copyright (C) 2011, 2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -21,14 +21,15 @@
#endif
/* Helper functions to issue warnings and errors when needed. */
-extern unsigned long int __fdelt_chk (unsigned long int __d);
-extern unsigned long int __fdelt_warn (unsigned long int __d)
+extern long int __fdelt_chk (long int __d);
+extern long int __fdelt_warn (long int __d)
__warnattr ("bit outside of fd_set selected");
#undef __FD_ELT
#define __FD_ELT(d) \
__extension__ \
- ({ unsigned long int __d = (d); \
+ ({ long int __d = (d); \
(__builtin_constant_p (__d) \
- ? (__d >= __FD_SETSIZE \
- ? __fdelt_warn (__d) : (__d / __NFDBITS)) \
+ ? (0 <= __d && __d < __FD_SETSIZE \
+ ? (__d / __NFDBITS) \
+ : __fdelt_warn (__d)) \
: __fdelt_chk (__d)); })