/usr/lib/gcc-cross/s390x-linux-gnu/7/plugin/include/is-a.h is in gcc-7-plugin-dev-s390x-linux-gnu 7.3.0-16ubuntu3cross1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 | /* Dynamic testing for abstract is-a relationships.
Copyright (C) 2012-2017 Free Software Foundation, Inc.
Contributed by Lawrence Crowl.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
/* This header generic type query and conversion functions.
USING THE GENERIC TYPE FACILITY
The user functions are:
bool is_a <TYPE> (pointer)
Tests whether the pointer actually points to a more derived TYPE.
Suppose you have a symtab_node *ptr, AKA symtab_node *ptr. You can test
whether it points to a 'derived' cgraph_node as follows.
if (is_a <cgraph_node *> (ptr))
....
TYPE as_a <TYPE> (pointer)
Converts pointer to a TYPE.
You can just assume that it is such a node.
do_something_with (as_a <cgraph_node *> *ptr);
TYPE safe_as_a <TYPE> (pointer)
Like as_a <TYPE> (pointer), but where pointer could be NULL. This
adds a check against NULL where the regular is_a_helper hook for TYPE
assumes non-NULL.
do_something_with (safe_as_a <cgraph_node *> *ptr);
TYPE dyn_cast <TYPE> (pointer)
Converts pointer to TYPE if and only if "is_a <TYPE> pointer". Otherwise,
returns NULL. This function is essentially a checked down cast.
This functions reduce compile time and increase type safety when treating a
generic item as a more specific item.
You can test and obtain a pointer to the 'derived' type in one indivisible
operation.
if (cgraph_node *cptr = dyn_cast <cgraph_node *> (ptr))
....
As an example, the code change is from
if (symtab_function_p (node))
{
struct cgraph_node *cnode = cgraph (node);
....
}
to
if (cgraph_node *cnode = dyn_cast <cgraph_node *> (node))
{
....
}
The necessary conditional test defines a variable that holds a known good
pointer to the specific item and avoids subsequent conversion calls and
the assertion checks that may come with them.
When, the property test is embedded within a larger condition, the
variable declaration gets pulled out of the condition. (This approach
leaves some room for using the variable inappropriately.)
if (symtab_variable_p (node) && varpool (node)->finalized)
varpool_analyze_node (varpool (node));
becomes
varpool_node *vnode = dyn_cast <varpool_node *> (node);
if (vnode && vnode->finalized)
varpool_analyze_node (vnode);
Note that we have converted two sets of assertions in the calls to varpool
into safe and efficient use of a variable.
TYPE safe_dyn_cast <TYPE> (pointer)
Like dyn_cast <TYPE> (pointer), except that it accepts null pointers
and returns null results for them.
If you use these functions and get a 'inline function not defined' or a
'missing symbol' error message for 'is_a_helper<....>::test', it means that
the connection between the types has not been made. See below.
EXTENDING THE GENERIC TYPE FACILITY
Each connection between types must be made by defining a specialization of the
template member function 'test' of the template class 'is_a_helper'. For
example,
template <>
template <>
inline bool
is_a_helper <cgraph_node *>::test (symtab_node *p)
{
return p->type == SYMTAB_FUNCTION;
}
If a simple reinterpret_cast between the pointer types is incorrect, then you
must also specialize the template member function 'cast'. Failure to do so
when needed may result in a crash. For example,
template <>
template <>
inline bool
is_a_helper <cgraph_node *>::cast (symtab_node *p)
{
return &p->x_function;
}
*/
#ifndef GCC_IS_A_H
#define GCC_IS_A_H
/* A generic type conversion internal helper class. */
template <typename T>
struct is_a_helper
{
template <typename U>
static inline bool test (U *p);
template <typename U>
static inline T cast (U *p);
};
/* Note that we deliberately do not define the 'test' member template. Not
doing so will result in a build-time error for type relationships that have
not been defined, rather than a run-time error. See the discussion above
for when to define this member. */
/* This is the generic implementation for casting from one type to another.
Do not use this routine directly; it is an internal function. See the
discussion above for when to define this member. */
template <typename T>
template <typename U>
inline T
is_a_helper <T>::cast (U *p)
{
return reinterpret_cast <T> (p);
}
/* The public interface. */
/* A generic test for a type relationship. See the discussion above for when
to use this function. The question answered is "Is type T a derived type of
type U?". */
template <typename T, typename U>
inline bool
is_a (U *p)
{
return is_a_helper<T>::test (p);
}
/* A generic conversion from a base type U to a derived type T. See the
discussion above for when to use this function. */
template <typename T, typename U>
inline T
as_a (U *p)
{
gcc_checking_assert (is_a <T> (p));
return is_a_helper <T>::cast (p);
}
/* Similar to as_a<>, but where the pointer can be NULL, even if
is_a_helper<T> doesn't check for NULL. */
template <typename T, typename U>
inline T
safe_as_a (U *p)
{
if (p)
{
gcc_checking_assert (is_a <T> (p));
return is_a_helper <T>::cast (p);
}
else
return NULL;
}
/* A generic checked conversion from a base type U to a derived type T. See
the discussion above for when to use this function. */
template <typename T, typename U>
inline T
dyn_cast (U *p)
{
if (is_a <T> (p))
return is_a_helper <T>::cast (p);
else
return static_cast <T> (0);
}
/* Similar to dyn_cast, except that the pointer may be null. */
template <typename T, typename U>
inline T
safe_dyn_cast (U *p)
{
return p ? dyn_cast <T> (p) : 0;
}
#endif /* GCC_IS_A_H */
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