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[Patch] Fix string::compare vs 64-bit
- From: Paolo Carlini <pcarlini at suse dot de>
- To: libstdc++ <libstdc++ at gcc dot gnu dot org>
- Date: Mon, 15 Jan 2007 20:19:04 +0100
- Subject: [Patch] Fix string::compare vs 64-bit
Hi,
today, while working on the warning issue, I noticed that we had a very
old problem for string::compare vs 64-bit arches, ultimately due to the
fact that those funtions are supposed to return an *int* everywhere:
basically, we are storing in an int the difference of two
string::size_type, which is 64-bits wide on 64-bit machines. I think we
can deal with the issue like in the below patch and I also tested that
on 32-bit machines the additional comparisons are optimized out.
Alternately, still conforming, we could also simply clip the result to
-1 and 1 but this option seems simpler but worse to me, because old v3
users may reasonably expect more than 1 bit of info out of compare when
the result is not zero...
Please let me know in case you find something wrong with the solution,
otherwise I will go ahead, mainline only for now.
Tested x86/x86_64-linux.
Paolo.
///////////////////
2007-01-15 Paolo Carlini <pcarlini@suse.de>
* include/bits/basic_string.h (basic_string<>::_S_compare): Add.
(compare(const basic_string&)): Use it.
* include/bits/basic_string.tcc (compare(size_type, size_type,
const basic_string&), compare(size_type, size_type,
const basic_string&, size_type, size_type), compare(const _CharT*),
compare(size_type, size_type, const _CharT*), compare(size_type,
size_type, const _CharT*, size_type)): Likewise.
* include/ext/vstring_util.h (__vstring_utility<>::_S_compare): Add.
* include/ext/vstring.h (compare(const __versa_string&)): Use it.
* include/ext/vstring.tcc (compare(size_type, size_type,
const __versa_string&), compare(size_type, size_type,
const __versa_string&, size_type, size_type), compare(const _CharT*),
compare(size_type, size_type, const _CharT*), compare(size_type,
size_type, const _CharT*, size_type)): Likewise.
Index: include/ext/vstring_util.h
===================================================================
--- include/ext/vstring_util.h (revision 120793)
+++ include/ext/vstring_util.h (working copy)
@@ -1,6 +1,6 @@
// Versatile string utility -*- C++ -*-
-// Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+// Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
@@ -55,6 +55,7 @@
typedef _Traits traits_type;
typedef typename _Traits::char_type value_type;
typedef typename _CharT_alloc_type::size_type size_type;
+ typedef typename _CharT_alloc_type::difference_type difference_type;
typedef typename _CharT_alloc_type::pointer pointer;
typedef typename _CharT_alloc_type::const_pointer const_pointer;
@@ -169,6 +170,19 @@
static void
_S_copy_chars(_CharT* __p, const _CharT* __k1, const _CharT* __k2)
{ _S_copy(__p, __k1, __k2 - __k1); }
+
+ static int
+ _S_compare(size_type __n1, size_type __n2)
+ {
+ const difference_type __d = difference_type(__n1 - __n2);
+
+ if (__d > std::numeric_limits<int>::max())
+ return std::numeric_limits<int>::max();
+ else if (__d < std::numeric_limits<int>::min())
+ return std::numeric_limits<int>::min();
+ else
+ return int(__d);
+ }
};
_GLIBCXX_END_NAMESPACE
Index: include/ext/vstring.h
===================================================================
--- include/ext/vstring.h (revision 120793)
+++ include/ext/vstring.h (working copy)
@@ -1,6 +1,6 @@
// Versatile string -*- C++ -*-
-// Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+// Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
@@ -1675,7 +1675,7 @@
int __r = traits_type::compare(this->_M_data(), __str.data(), __len);
if (!__r)
- __r = __size - __osize;
+ __r = _S_compare(__size, __osize);
return __r;
}
Index: include/ext/vstring.tcc
===================================================================
--- include/ext/vstring.tcc (revision 120793)
+++ include/ext/vstring.tcc (working copy)
@@ -1,6 +1,6 @@
// Versatile string -*- C++ -*-
-// Copyright (C) 2005, 2006 Free Software Foundation, Inc.
+// Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
@@ -467,7 +467,7 @@
int __r = traits_type::compare(this->_M_data() + __pos,
__str.data(), __len);
if (!__r)
- __r = __n - __osize;
+ __r = _S_compare(__n, __osize);
return __r;
}
@@ -486,7 +486,7 @@
int __r = traits_type::compare(this->_M_data() + __pos1,
__str.data() + __pos2, __len);
if (!__r)
- __r = __n1 - __n2;
+ __r = _S_compare(__n1, __n2);
return __r;
}
@@ -502,7 +502,7 @@
const size_type __len = std::min(__size, __osize);
int __r = traits_type::compare(this->_M_data(), __s, __len);
if (!__r)
- __r = __size - __osize;
+ __r = _S_compare(__size, __osize);
return __r;
}
@@ -519,7 +519,7 @@
const size_type __len = std::min(__n1, __osize);
int __r = traits_type::compare(this->_M_data() + __pos, __s, __len);
if (!__r)
- __r = __n1 - __osize;
+ __r = _S_compare(__n1, __osize);
return __r;
}
@@ -536,7 +536,7 @@
const size_type __len = std::min(__n1, __n2);
int __r = traits_type::compare(this->_M_data() + __pos, __s, __len);
if (!__r)
- __r = __n1 - __n2;
+ __r = _S_compare(__n1, __n2);
return __r;
}
Index: include/bits/basic_string.h
===================================================================
--- include/bits/basic_string.h (revision 120792)
+++ include/bits/basic_string.h (working copy)
@@ -1,6 +1,7 @@
// Components for manipulating sequences of characters -*- C++ -*-
-// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
+// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+// 2006, 2007
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
@@ -389,6 +390,19 @@
_S_copy_chars(_CharT* __p, const _CharT* __k1, const _CharT* __k2)
{ _M_copy(__p, __k1, __k2 - __k1); }
+ static int
+ _S_compare(size_type __n1, size_type __n2)
+ {
+ const difference_type __d = difference_type(__n1 - __n2);
+
+ if (__d > numeric_limits<int>::max())
+ return numeric_limits<int>::max();
+ else if (__d < numeric_limits<int>::min())
+ return numeric_limits<int>::min();
+ else
+ return int(__d);
+ }
+
void
_M_mutate(size_type __pos, size_type __len1, size_type __len2);
@@ -1933,7 +1947,7 @@
int __r = traits_type::compare(_M_data(), __str.data(), __len);
if (!__r)
- __r = __size - __osize;
+ __r = _S_compare(__size, __osize);
return __r;
}
Index: include/bits/basic_string.tcc
===================================================================
--- include/bits/basic_string.tcc (revision 120792)
+++ include/bits/basic_string.tcc (working copy)
@@ -1,6 +1,7 @@
// Components for manipulating sequences of characters -*- C++ -*-
-// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
+// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
+// 2006, 2007
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
@@ -902,7 +903,7 @@
const size_type __len = std::min(__n, __osize);
int __r = traits_type::compare(_M_data() + __pos, __str.data(), __len);
if (!__r)
- __r = __n - __osize;
+ __r = _S_compare(__n, __osize);
return __r;
}
@@ -920,7 +921,7 @@
int __r = traits_type::compare(_M_data() + __pos1,
__str.data() + __pos2, __len);
if (!__r)
- __r = __n1 - __n2;
+ __r = _S_compare(__n1, __n2);
return __r;
}
@@ -935,7 +936,7 @@
const size_type __len = std::min(__size, __osize);
int __r = traits_type::compare(_M_data(), __s, __len);
if (!__r)
- __r = __size - __osize;
+ __r = _S_compare(__size, __osize);
return __r;
}
@@ -951,7 +952,7 @@
const size_type __len = std::min(__n1, __osize);
int __r = traits_type::compare(_M_data() + __pos, __s, __len);
if (!__r)
- __r = __n1 - __osize;
+ __r = _S_compare(__n1, __osize);
return __r;
}
@@ -967,7 +968,7 @@
const size_type __len = std::min(__n1, __n2);
int __r = traits_type::compare(_M_data() + __pos, __s, __len);
if (!__r)
- __r = __n1 - __n2;
+ __r = _S_compare(__n1, __n2);
return __r;
}