Mercurial > hg > CbC > CbC_gcc
comparison gcc/cp/NEWS @ 111:04ced10e8804
gcc 7
author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |
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children | 84e7813d76e9 |
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68:561a7518be6b | 111:04ced10e8804 |
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1 *** Changes in GCC 3.4: | |
2 | |
3 * Changes in GCC 3.4 are described in 'gcc-3.4/changes.html' | |
4 | |
5 *** Changes in GCC 3.3: | |
6 | |
7 * The "new X = 3" extension has been removed; you must now use "new X(3)". | |
8 | |
9 * G++ no longer allows in-class initializations of static data members | |
10 that do not have arithmetic or enumeration type. For example: | |
11 | |
12 struct S { | |
13 static const char* const p = "abc"; | |
14 }; | |
15 | |
16 is no longer accepted. | |
17 | |
18 Use the standards-conformant form: | |
19 | |
20 struct S { | |
21 static const char* const p; | |
22 }; | |
23 | |
24 const char* const S::p = "abc"; | |
25 | |
26 instead. | |
27 | |
28 (ISO C++ is even stricter; it does not allow in-class | |
29 initializations of floating-point types.) | |
30 | |
31 *** Changes in GCC 3.1: | |
32 | |
33 * -fhonor-std and -fno-honor-std have been removed. -fno-honor-std was | |
34 a workaround to allow std compliant code to work with the non-std | |
35 compliant libstdc++-v2. libstdc++-v3 is std compliant. | |
36 | |
37 * The C++ ABI has been fixed so that `void (A::*)() const' is mangled as | |
38 "M1AKFvvE", rather than "MK1AFvvE" as before. This change only affects | |
39 pointer to cv-qualified member function types. | |
40 | |
41 * The C++ ABI has been changed to correctly handle this code: | |
42 | |
43 struct A { | |
44 void operator delete[] (void *, size_t); | |
45 }; | |
46 | |
47 struct B : public A { | |
48 }; | |
49 | |
50 new B[10]; | |
51 | |
52 The amount of storage allocated for the array will be greater than | |
53 it was in 3.0, in order to store the number of elements in the | |
54 array, so that the correct size can be passed to `operator delete[]' | |
55 when the array is deleted. Previously, the value passed to | |
56 `operator delete[]' was unpredictable. | |
57 | |
58 This change will only affect code that declares a two-argument | |
59 `operator delete[]' with a second parameter of type `size_t' | |
60 in a base class, and does not override that definition in a | |
61 derived class. | |
62 | |
63 * The C++ ABI has been changed so that: | |
64 | |
65 struct A { | |
66 void operator delete[] (void *, size_t); | |
67 void operator delete[] (void *); | |
68 }; | |
69 | |
70 does not cause unnecessary storage to be allocated when an array of | |
71 `A' objects is allocated. | |
72 | |
73 This change will only affect code that declares both of these | |
74 forms of `operator delete[]', and declared the two-argument form | |
75 before the one-argument form. | |
76 | |
77 * The C++ ABI has been changed so that when a parameter is passed by value, | |
78 any cleanup for that parameter is performed in the caller, as specified | |
79 by the ia64 C++ ABI, rather than the called function as before. As a | |
80 result, classes with a non-trivial destructor but a trivial copy | |
81 constructor will be passed and returned by invisible reference, rather | |
82 than by bitwise copy as before. | |
83 | |
84 * G++ now supports the "named return value optimization": for code like | |
85 | |
86 A f () { | |
87 A a; | |
88 ... | |
89 return a; | |
90 } | |
91 | |
92 G++ will allocate 'a' in the return value slot, so that the return | |
93 becomes a no-op. For this to work, all return statements in the function | |
94 must return the same variable. | |
95 | |
96 *** Changes in GCC 3.0: | |
97 | |
98 * Support for guiding declarations has been removed. | |
99 | |
100 * G++ now supports importing member functions from base classes with a | |
101 using-declaration. | |
102 | |
103 * G++ now enforces access control for nested types. | |
104 | |
105 * In some obscure cases, functions with the same type could have the | |
106 same mangled name. This bug caused compiler crashes, link-time clashes, | |
107 and debugger crashes. Fixing this bug required breaking ABI | |
108 compatibility for the functions involved. The functions in questions | |
109 are those whose types involve non-type template arguments whose | |
110 mangled representations require more than one digit. | |
111 | |
112 * Support for assignment to `this' has been removed. This idiom | |
113 was used in the very early days of C++, before users were allowed | |
114 to overload `operator new'; it is no longer allowed by the C++ | |
115 standard. | |
116 | |
117 * Support for signatures, a G++ extension, have been removed. | |
118 | |
119 * Certain invalid conversions that were previously accepted will now | |
120 be rejected. For example, assigning function pointers of one type | |
121 to function pointers of another type now requires a cast, whereas | |
122 previously g++ would sometimes accept the code even without the | |
123 cast. | |
124 | |
125 * G++ previously allowed `sizeof (X::Y)' where Y was a non-static | |
126 member of X, even if the `sizeof' expression occurred outside | |
127 of a non-static member function of X (or one of its derived classes, | |
128 or a member-initializer for X or one of its derived classes.) This | |
129 extension has been removed. | |
130 | |
131 * G++ no longer allows you to overload the conditional operator (i.e., | |
132 the `?:' operator.) | |
133 | |
134 * The "named return value" extension: | |
135 | |
136 int f () return r { r = 3; } | |
137 | |
138 has been deprecated, and will be removed in a future version of G++. | |
139 | |
140 *** Changes in GCC 2.95: | |
141 | |
142 * Messages about non-conformant code that we can still handle ("pedwarns") | |
143 are now errors by default, rather than warnings. This can be reverted | |
144 with -fpermissive, and is overridden by -pedantic or -pedantic-errors. | |
145 | |
146 * String constants are now of type `const char[n]', rather than `char[n]'. | |
147 This can be reverted with -fno-const-strings. | |
148 | |
149 * References to functions are now supported. | |
150 | |
151 * Lookup of class members during class definition now works in all cases. | |
152 | |
153 * In overload resolution, type conversion operators are now properly | |
154 treated as always coming from the most derived class. | |
155 | |
156 * C9x-style restricted pointers are supported, using the `__restrict' | |
157 keyword. | |
158 | |
159 * You can now use -fno-implicit-inline-templates to suppress writing out | |
160 implicit instantiations of inline templates. Normally we do write them | |
161 out, even with -fno-implicit-templates, so that optimization doesn't | |
162 affect which instantiations are needed. | |
163 | |
164 * -fstrict-prototype now also suppresses implicit declarations. | |
165 | |
166 * Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups, | |
167 -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects. | |
168 | |
169 * Unused virtual functions can be discarded on some targets by specifying | |
170 -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the | |
171 linker. Unfortunately, this only works on GNU/Linux if you're linking | |
172 statically. | |
173 | |
174 * Lots of bugs stomped. | |
175 | |
176 *** Changes in EGCS 1.1: | |
177 | |
178 * Namespaces are fully supported. The library has not yet been converted | |
179 to use namespace std, however, and the old std-faking code is still on by | |
180 default. To turn it off, you can use -fhonor-std. | |
181 | |
182 * Massive template improvements: | |
183 + member template classes are supported. | |
184 + template friends are supported. | |
185 + template template parameters are supported. | |
186 + local classes in templates are supported. | |
187 + lots of bugs fixed. | |
188 | |
189 * operator new now throws bad_alloc where appropriate. | |
190 | |
191 * Exception handling is now thread safe, and supports nested exceptions and | |
192 placement delete. Exception handling overhead on x86 is much lower with | |
193 GNU as 2.9. | |
194 | |
195 * protected virtual inheritance is now supported. | |
196 | |
197 * Loops are optimized better; we now move the test to the end in most | |
198 cases, like the C frontend does. | |
199 | |
200 * For class D derived from B which has a member 'int i', &D::i is now of | |
201 type 'int B::*' instead of 'int D::*'. | |
202 | |
203 * An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The | |
204 current features of this are more efficient allocation of base classes | |
205 (including the empty base optimization), and more compact mangling of C++ | |
206 symbol names (which can be turned on separately with -fsquangle). This | |
207 ABI is subject to change without notice, so don't use it for anything | |
208 that you don't want to rebuild with every release of the compiler. | |
209 | |
210 As with all ABI-changing flags, this flag is for experts only, as all | |
211 code (including the library code in libgcc and libstdc++) must be | |
212 compiled with the same ABI. | |
213 | |
214 *** Changes in EGCS 1.0: | |
215 | |
216 * A public review copy of the December 1996 Draft of the ISO/ANSI C++ | |
217 standard is now available. See | |
218 | |
219 http://www.cygnus.com/misc/wp/ | |
220 | |
221 for more information. | |
222 | |
223 * g++ now uses a new implementation of templates. The basic idea is that | |
224 now templates are minimally parsed when seen and then expanded later. | |
225 This allows conformant early name binding and instantiation controls, | |
226 since instantiations no longer have to go through the parser. | |
227 | |
228 What you get: | |
229 | |
230 + Inlining of template functions works without any extra effort or | |
231 modifications. | |
232 + Instantiations of class templates and methods defined in the class | |
233 body are deferred until they are actually needed (unless | |
234 -fexternal-templates is specified). | |
235 + Nested types in class templates work. | |
236 + Static data member templates work. | |
237 + Member function templates are now supported. | |
238 + Partial specialization of class templates is now supported. | |
239 + Explicit specification of template parameters to function templates | |
240 is now supported. | |
241 | |
242 Things you may need to fix in your code: | |
243 | |
244 + Syntax errors in templates that are never instantiated will now be | |
245 diagnosed. | |
246 + Types and class templates used in templates must be declared | |
247 first, or the compiler will assume they are not types, and fail. | |
248 + Similarly, nested types of template type parameters must be tagged | |
249 with the 'typename' keyword, except in base lists. In many cases, | |
250 but not all, the compiler will tell you where you need to add | |
251 'typename'. For more information, see | |
252 | |
253 http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res | |
254 | |
255 + Guiding declarations are no longer supported. Function declarations, | |
256 including friend declarations, do not refer to template instantiations. | |
257 You can restore the old behavior with -fguiding-decls until you fix | |
258 your code. | |
259 | |
260 Other features: | |
261 | |
262 + Default function arguments in templates will not be evaluated (or | |
263 checked for semantic validity) unless they are needed. Default | |
264 arguments in class bodies will not be parsed until the class | |
265 definition is complete. | |
266 + The -ftemplate-depth-NN flag can be used to increase the maximum | |
267 recursive template instantiation depth, which defaults to 17. If you | |
268 need to use this flag, the compiler will tell you. | |
269 + Explicit instantiation of template constructors and destructors is | |
270 now supported. For instance: | |
271 | |
272 template A<int>::A(const A&); | |
273 | |
274 Still not supported: | |
275 | |
276 + Member class templates. | |
277 + Template friends. | |
278 | |
279 * Exception handling support has been significantly improved and is on by | |
280 default. The compiler supports two mechanisms for walking back up the | |
281 call stack; one relies on static information about how registers are | |
282 saved, and causes no runtime overhead for code that does not throw | |
283 exceptions. The other mechanism uses setjmp and longjmp equivalents, and | |
284 can result in quite a bit of runtime overhead. You can determine which | |
285 mechanism is the default for your target by compiling a testcase that | |
286 uses exceptions and doing an 'nm' on the object file; if it uses __throw, | |
287 it's using the first mechanism. If it uses __sjthrow, it's using the | |
288 second. | |
289 | |
290 You can turn EH support off with -fno-exceptions. | |
291 | |
292 * RTTI support has been rewritten to work properly and is now on by default. | |
293 This means code that uses virtual functions will have a modest space | |
294 overhead. You can use the -fno-rtti flag to disable RTTI support. | |
295 | |
296 * On ELF systems, duplicate copies of symbols with 'initialized common' | |
297 linkage (such as template instantiations, vtables, and extern inlines) | |
298 will now be discarded by the GNU linker, so you don't need to use -frepo. | |
299 This support requires GNU ld from binutils 2.8 or later. | |
300 | |
301 * The overload resolution code has been rewritten to conform to the latest | |
302 C++ Working Paper. Built-in operators are now considered as candidates | |
303 in operator overload resolution. Function template overloading chooses | |
304 the more specialized template, and handles base classes in type deduction | |
305 and guiding declarations properly. In this release the old code can | |
306 still be selected with -fno-ansi-overloading, although this is not | |
307 supported and will be removed in a future release. | |
308 | |
309 * Standard usage syntax for the std namespace is supported; std is treated | |
310 as an alias for global scope. General namespaces are still not supported. | |
311 | |
312 * New flags: | |
313 | |
314 + New warning -Wno-pmf-conversion (don't warn about | |
315 converting from a bound member function pointer to function | |
316 pointer). | |
317 | |
318 + A flag -Weffc++ has been added for violations of some of the style | |
319 guidelines in Scott Meyers' _Effective C++_ books. | |
320 | |
321 + -Woverloaded-virtual now warns if a virtual function in a base | |
322 class is hidden in a derived class, rather than warning about | |
323 virtual functions being overloaded (even if all of the inherited | |
324 signatures are overridden) as it did before. | |
325 | |
326 + -Wall no longer implies -W. The new warning flag, -Wsign-compare, | |
327 included in -Wall, warns about dangerous comparisons of signed and | |
328 unsigned values. Only the flag is new; it was previously part of | |
329 -W. | |
330 | |
331 + The new flag, -fno-weak, disables the use of weak symbols. | |
332 | |
333 * Synthesized methods are now emitted in any translation units that need | |
334 an out-of-line copy. They are no longer affected by #pragma interface | |
335 or #pragma implementation. | |
336 | |
337 * __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the | |
338 parser; previously they were treated as string constants. So code like | |
339 `printf (__FUNCTION__ ": foo")' must be rewritten to | |
340 `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. | |
341 | |
342 * local static variables in extern inline functions will be shared between | |
343 translation units. | |
344 | |
345 * -fvtable-thunks is supported for all targets, and is the default for | |
346 GNU/Linux with glibc 2.x (also called libc 6.x). | |
347 | |
348 * bool is now always the same size as another built-in type. Previously, | |
349 a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a | |
350 64-bit bool. This should only affect Irix 6, which was not supported in | |
351 2.7.2. | |
352 | |
353 * new (nothrow) is now supported. | |
354 | |
355 * Synthesized destructors are no longer made virtual just because the class | |
356 already has virtual functions, only if they override a virtual destructor | |
357 in a base class. The compiler will warn if this affects your code. | |
358 | |
359 * The g++ driver now only links against libstdc++, not libg++; it is | |
360 functionally identical to the c++ driver. | |
361 | |
362 * (void *)0 is no longer considered a null pointer constant; NULL in | |
363 <stddef.h> is now defined as __null, a magic constant of type (void *) | |
364 normally, or (size_t) with -ansi. | |
365 | |
366 * The name of a class is now implicitly declared in its own scope; A::A | |
367 refers to A. | |
368 | |
369 * Local classes are now supported. | |
370 | |
371 * __attribute__ can now be attached to types as well as declarations. | |
372 | |
373 * The compiler no longer emits a warning if an ellipsis is used as a | |
374 function's argument list. | |
375 | |
376 * Definition of nested types outside of their containing class is now | |
377 supported. For instance: | |
378 | |
379 struct A { | |
380 struct B; | |
381 B* bp; | |
382 }; | |
383 | |
384 struct A::B { | |
385 int member; | |
386 }; | |
387 | |
388 * On the HPPA, some classes that do not define a copy constructor | |
389 will be passed and returned in memory again so that functions | |
390 returning those types can be inlined. | |
391 | |
392 *** The g++ team thanks everyone that contributed to this release, | |
393 but especially: | |
394 | |
395 * Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. | |
396 * Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. | |
397 * Jason Merrill <jason@cygnus.com>, the g++ maintainer. | |
398 * Mark Mitchell <mmitchell@usa.net>, who implemented member function | |
399 templates and explicit qualification of function templates. | |
400 * Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of | |
401 the exception handling work. | |
402 | |
403 | |
404 Copyright (C) 1997-2017 Free Software Foundation, Inc. | |
405 | |
406 Copying and distribution of this file, with or without modification, | |
407 are permitted in any medium without royalty provided the copyright | |
408 notice and this notice are preserved. |