[PATCH] Suppress sign-conversion warning from FD_SET

[Paul Pluzhnikov]

On Sat, May 26, 2012 at 10:49 AM, Paul Eggert <eggert@cs.ucla.edu> wrote:
>  +extern unsigned long int __fdelt_chk (long int __d);
>  +extern unsigned long int __fdelt_warn (long int __d)
>
> Shouldn't these functions return the same type
> that they accept?

Probably.

> -  ({ unsigned long int __d = (d);                                          \
> +  ({ long int __d = (d);                                                   \
>      (__builtin_constant_p (__d)                                           \
>       ? (__d >= __FD_SETSIZE                                               \
>
> This should check for __d < 0 as well.
> Or, to make it clearer, you might write it this way:
>
>    (0 <= d && d < __FD_SETSIZE
>     ? __d / __NFDBITS
>     : __fdelt_warn (__d))

Ok.

Thanks,
-- 
Paul Pluzhnikov


2012-05-28  Paul Pluzhnikov  <ppluzhnikov@google.com>

       * debug/fdelt_chk.c (__fdelt_chk): Use signed long to avoid warning.
       * misc/bits/select2.h (__FD_ELT): Adjust for above.
-------------- next part --------------
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..5650abc 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 && __FD_SETSIZE < __d					    \
+	 ? (__d / __NFDBITS)						    \
+	 : __fdelt_warn (__d))						    \
       : __fdelt_chk (__d)); })