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Commit | Line | Data |
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a723baf1 MM |
1 | *** Changes in GCC 3.4: |
2 | ||
3 | * The C++ parser in G++ has been rewritten from scratch. As a result, G++ | |
4 | is considerably more compliant to the C++ standard. As a result, it | |
5 | accepts more valid programs, and rejects more invalid programs. | |
6 | ||
7 | Many of the changes below are a consequence of the new parser. | |
8 | ||
9 | * Friend declarations that refer to template specializations are rejected | |
10 | if the template has not already been declared. | |
11 | ||
12 | For example: | |
13 | ||
14 | template <typename T> | |
15 | class C { | |
16 | friend void f<>(C&); | |
17 | }; | |
18 | ||
19 | is rejected; you must first declare `f' as a template: | |
20 | ||
21 | template <typename T> | |
22 | void f(T); | |
23 | ||
24 | * You must use "template <>" to introduce template specializations, as | |
25 | required by the standard. For example: | |
26 | ||
27 | template <typename T> | |
28 | struct S; | |
29 | ||
30 | struct S<int> { }; | |
31 | ||
32 | is rejected; you must write: | |
33 | ||
34 | template <> struct S<int> {}; | |
35 | ||
36 | * You must now use the `typename' and `template' keywords to disambiguate | |
37 | dependent names, as required by the C++ standard. | |
38 | ||
39 | * The "named return value" extension has been removed. | |
40 | ||
41 | * The "implicit typename" extension has been removed. | |
42 | ||
43 | * G++ used to accept code like this: | |
44 | ||
45 | struct S { | |
46 | int h(); | |
47 | void f(int i = g()); | |
48 | int g(int i = h()); | |
49 | }; | |
50 | ||
51 | This behavior is not mandated by the standard. | |
52 | ||
53 | Now G++ issues an error about this code. To avoid the error, you must | |
54 | move the declaration of `g' before the declaration of `f'. The | |
55 | default arguments for `g' must be visible at the point where it is | |
56 | called. | |
57 | ||
58 | * When -pedantic is used, G++ now issues errors about spurious semicolons; | |
59 | for example: | |
60 | ||
61 | namespace N {}; // Invalid semicolon. | |
62 | void f() {}; // Invalid semicolon. | |
63 | ||
64 | * G++ no longer accepts attributes for a declarator after the | |
65 | initializer associated with that declarator. For example: | |
66 | ||
67 | X x(1) __attribute__((...)); | |
68 | ||
69 | is no longer accepted. Instead, use: | |
70 | ||
71 | X x __attribute__((...)) (1); | |
72 | ||
8e3df2de MM |
73 | *** Changes in GCC 3.3: |
74 | ||
75 | * The "new X = 3" extension has been removed; you must now use "new X(3)". | |
76 | ||
dcba9b0f MM |
77 | * G++ no longer allows in-class initializations of static data members |
78 | that do not have arithmetic or enumeration type. For example: | |
79 | ||
80 | struct S { | |
81 | static const char* const p = "abc"; | |
82 | }; | |
83 | ||
84 | is no longer accepted. | |
85 | ||
86 | Use the standards-conformant form: | |
87 | ||
88 | struct S { | |
89 | static const char* const p; | |
90 | }; | |
91 | ||
92 | const char* const S::p = "abc"; | |
93 | ||
94 | instead. | |
95 | ||
96 | (ISO C++ is even stricter; it does not allow in-class | |
97 | initializations of floating-point types.) | |
98 | ||
e065a36e MM |
99 | *** Changes in GCC 3.1: |
100 | ||
1dbb6023 NS |
101 | * -fhonor-std and -fno-honor-std have been removed. -fno-honor-std was |
102 | a workaround to allow std compliant code to work with the non-std | |
103 | compliant libstdc++-v2. libstdc++-v3 is std compliant. | |
104 | ||
e61d6d83 JM |
105 | * The C++ ABI has been fixed so that `void (A::*)() const' is mangled as |
106 | "M1AKFvvE", rather than "MK1AFvvE" as before. This change only affects | |
107 | pointer to cv-qualified member function types. | |
108 | ||
dbc957f1 MM |
109 | * The C++ ABI has been changed to correctly handle this code: |
110 | ||
111 | struct A { | |
112 | void operator delete[] (void *, size_t); | |
113 | }; | |
114 | ||
115 | struct B : public A { | |
116 | }; | |
117 | ||
118 | new B[10]; | |
119 | ||
120 | The amount of storage allocated for the array will be greater than | |
121 | it was in 3.0, in order to store the number of elements in the | |
122 | array, so that the correct size can be passed to `operator delete[]' | |
123 | when the array is deleted. Previously, the value passed to | |
124 | `operator delete[]' was unpredictable. | |
125 | ||
126 | This change will only affect code that declares a two-argument | |
127 | `operator delete[]' with a second parameter of type `size_t' | |
128 | in a base class, and does not override that definition in a | |
129 | derived class. | |
130 | ||
131 | * The C++ ABI has been changed so that: | |
132 | ||
133 | struct A { | |
134 | void operator delete[] (void *, size_t); | |
135 | void operator delete[] (void *); | |
136 | }; | |
137 | ||
aba649ba | 138 | does not cause unnecessary storage to be allocated when an array of |
dbc957f1 MM |
139 | `A' objects is allocated. |
140 | ||
141 | This change will only affect code that declares both of these | |
142 | forms of `operator delete[]', and declared the two-argument form | |
143 | before the one-argument form. | |
144 | ||
f21add07 JM |
145 | * The C++ ABI has been changed so that when a parameter is passed by value, |
146 | any cleanup for that parameter is performed in the caller, as specified | |
fd70bb64 JM |
147 | by the ia64 C++ ABI, rather than the called function as before. As a |
148 | result, classes with a non-trivial destructor but a trivial copy | |
149 | constructor will be passed and returned by invisible reference, rather | |
150 | than by bitwise copy as before. | |
f21add07 | 151 | |
d6b2c474 JM |
152 | * G++ now supports the "named return value optimization": for code like |
153 | ||
154 | A f () { | |
155 | A a; | |
156 | ... | |
157 | return a; | |
158 | } | |
159 | ||
160 | G++ will allocate 'a' in the return value slot, so that the return | |
161 | becomes a no-op. For this to work, all return statements in the function | |
162 | must return the same variable. | |
163 | ||
e065a36e | 164 | *** Changes in GCC 3.0: |
9fe94fd3 | 165 | |
2228d450 MM |
166 | * Support for guiding declarations has been removed. |
167 | ||
9fe94fd3 JM |
168 | * G++ now supports importing member functions from base classes with a |
169 | using-declaration. | |
170 | ||
171 | * G++ now enforces access control for nested types. | |
5bb2f1e7 | 172 | |
858a0ff1 MM |
173 | * In some obscure cases, functions with the same type could have the |
174 | same mangled name. This bug caused compiler crashes, link-time clashes, | |
7ba0b0f7 | 175 | and debugger crashes. Fixing this bug required breaking ABI |
858a0ff1 MM |
176 | compatibility for the functions involved. The functions in questions |
177 | are those whose types involve non-type template arguments whose | |
178 | mangled representations require more than one digit. | |
179 | ||
9bfadf57 MM |
180 | * Support for assignment to `this' has been removed. This idiom |
181 | was used in the very early days of C++, before users were allowed | |
182 | to overload `operator new'; it is no longer allowed by the C++ | |
183 | standard. | |
184 | ||
cf7cf3d2 MM |
185 | * Support for signatures, a G++ extension, have been removed. |
186 | ||
5bb2f1e7 MM |
187 | * Certain invalid conversions that were previously accepted will now |
188 | be rejected. For example, assigning function pointers of one type | |
189 | to function pointers of another type now requires a cast, whereas | |
190 | previously g++ would sometimes accept the code even without the | |
191 | cast. | |
192 | ||
193 | * G++ previously allowed `sizeof (X::Y)' where Y was a non-static | |
194 | member of X, even if the `sizeof' expression occurred outside | |
195 | of a non-static member function of X (or one of its derived classes, | |
196 | or a member-initializer for X or one of its derived classes.) This | |
197 | extension has been removed. | |
198 | ||
199 | * G++ no longer allows you to overload the conditional operator (i.e., | |
200 | the `?:' operator.) | |
201 | ||
44835fdd MM |
202 | * The "named return value" extension: |
203 | ||
204 | int f () return r { r = 3; } | |
205 | ||
206 | has been deprecated, and will be removed in a future version of G++. | |
207 | ||
b1b9b120 | 208 | *** Changes in GCC 2.95: |
2642b9bf JM |
209 | |
210 | * Messages about non-conformant code that we can still handle ("pedwarns") | |
211 | are now errors by default, rather than warnings. This can be reverted | |
212 | with -fpermissive, and is overridden by -pedantic or -pedantic-errors. | |
213 | ||
b1b9b120 JM |
214 | * String constants are now of type `const char[n]', rather than `char[n]'. |
215 | This can be reverted with -fno-const-strings. | |
216 | ||
217 | * References to functions are now supported. | |
218 | ||
219 | * Lookup of class members during class definition now works in all cases. | |
220 | ||
221 | * In overload resolution, type conversion operators are now properly | |
222 | treated as always coming from the most derived class. | |
223 | ||
224 | * C9x-style restricted pointers are supported, using the `__restrict' | |
225 | keyword. | |
226 | ||
227 | * You can now use -fno-implicit-inline-templates to suppress writing out | |
228 | implicit instantiations of inline templates. Normally we do write them | |
229 | out, even with -fno-implicit-templates, so that optimization doesn't | |
230 | affect which instantiations are needed. | |
231 | ||
232 | * -fstrict-prototype now also suppresses implicit declarations. | |
233 | ||
234 | * Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups, | |
235 | -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects. | |
236 | ||
237 | * Unused virtual functions can be discarded on some targets by specifying | |
238 | -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the | |
239 | linker. Unfortunately, this only works on Linux if you're linking | |
240 | statically. | |
241 | ||
242 | * Lots of bugs stomped. | |
243 | ||
1a408d07 | 244 | *** Changes in EGCS 1.1: |
be343556 | 245 | |
d1fec180 JM |
246 | * Namespaces are fully supported. The library has not yet been converted |
247 | to use namespace std, however, and the old std-faking code is still on by | |
248 | default. To turn it off, you can use -fhonor-std. | |
249 | ||
570221c2 JM |
250 | * Massive template improvements: |
251 | + member template classes are supported. | |
252 | + template friends are supported. | |
253 | + template template parameters are supported. | |
254 | + local classes in templates are supported. | |
255 | + lots of bugs fixed. | |
be343556 JM |
256 | |
257 | * operator new now throws bad_alloc where appropriate. | |
258 | ||
d1fec180 JM |
259 | * Exception handling is now thread safe, and supports nested exceptions and |
260 | placement delete. Exception handling overhead on x86 is much lower with | |
261 | GNU as 2.9. | |
570221c2 JM |
262 | |
263 | * protected virtual inheritance is now supported. | |
264 | ||
265 | * Loops are optimized better; we now move the test to the end in most | |
266 | cases, like the C frontend does. | |
267 | ||
268 | * For class D derived from B which has a member 'int i', &D::i is now of | |
269 | type 'int B::*' instead of 'int D::*'. | |
270 | ||
d1fec180 JM |
271 | * An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The |
272 | current features of this are more efficient allocation of base classes | |
273 | (including the empty base optimization), and more compact mangling of C++ | |
274 | symbol names (which can be turned on separately with -fsquangle). This | |
275 | ABI is subject to change without notice, so don't use it for anything | |
276 | that you don't want to rebuild with every release of the compiler. | |
277 | ||
cb99b4a0 JM |
278 | As with all ABI-changing flags, this flag is for experts only, as all |
279 | code (including the library code in libgcc and libstdc++) must be | |
280 | compiled with the same ABI. | |
281 | ||
be343556 | 282 | *** Changes in EGCS 1.0: |
fb52f6de | 283 | |
19754d4c JM |
284 | * A public review copy of the December 1996 Draft of the ISO/ANSI C++ |
285 | standard is now available. See | |
fb52f6de JM |
286 | |
287 | http://www.cygnus.com/misc/wp/ | |
288 | ||
289 | for more information. | |
290 | ||
1e60a96e JM |
291 | * g++ now uses a new implementation of templates. The basic idea is that |
292 | now templates are minimally parsed when seen and then expanded later. | |
293 | This allows conformant early name binding and instantiation controls, | |
294 | since instantiations no longer have to go through the parser. | |
295 | ||
296 | What you get: | |
297 | ||
298 | + Inlining of template functions works without any extra effort or | |
299 | modifications. | |
1e60a96e JM |
300 | + Instantiations of class templates and methods defined in the class |
301 | body are deferred until they are actually needed (unless | |
302 | -fexternal-templates is specified). | |
1e60a96e | 303 | + Nested types in class templates work. |
1e60a96e | 304 | + Static data member templates work. |
1e60a96e | 305 | + Member function templates are now supported. |
1e60a96e | 306 | + Partial specialization of class templates is now supported. |
386b8a85 JM |
307 | + Explicit specification of template parameters to function templates |
308 | is now supported. | |
1e60a96e | 309 | |
405a745b | 310 | Things you may need to fix in your code: |
1e60a96e | 311 | |
405a745b JM |
312 | + Syntax errors in templates that are never instantiated will now be |
313 | diagnosed. | |
1e60a96e JM |
314 | + Types and class templates used in templates must be declared |
315 | first, or the compiler will assume they are not types, and fail. | |
1e60a96e | 316 | + Similarly, nested types of template type parameters must be tagged |
405a745b JM |
317 | with the 'typename' keyword, except in base lists. In many cases, |
318 | but not all, the compiler will tell you where you need to add | |
319 | 'typename'. For more information, see | |
1e60a96e | 320 | |
405a745b | 321 | http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res |
1e60a96e | 322 | |
386b8a85 JM |
323 | + Guiding declarations are no longer supported. Function declarations, |
324 | including friend declarations, do not refer to template instantiations. | |
325 | You can restore the old behavior with -fguiding-decls until you fix | |
326 | your code. | |
327 | ||
1e60a96e JM |
328 | Other features: |
329 | ||
330 | + Default function arguments in templates will not be evaluated (or | |
331 | checked for semantic validity) unless they are needed. Default | |
332 | arguments in class bodies will not be parsed until the class | |
333 | definition is complete. | |
1e60a96e | 334 | + The -ftemplate-depth-NN flag can be used to increase the maximum |
405a745b JM |
335 | recursive template instantiation depth, which defaults to 17. If you |
336 | need to use this flag, the compiler will tell you. | |
386b8a85 JM |
337 | + Explicit instantiation of template constructors and destructors is |
338 | now supported. For instance: | |
339 | ||
340 | template A<int>::A(const A&); | |
1e60a96e JM |
341 | |
342 | Still not supported: | |
343 | ||
405a745b | 344 | + Member class templates. |
405a745b | 345 | + Template friends. |
1e60a96e JM |
346 | |
347 | * Exception handling support has been significantly improved and is on by | |
19754d4c JM |
348 | default. The compiler supports two mechanisms for walking back up the |
349 | call stack; one relies on static information about how registers are | |
350 | saved, and causes no runtime overhead for code that does not throw | |
351 | exceptions. The other mechanism uses setjmp and longjmp equivalents, and | |
352 | can result in quite a bit of runtime overhead. You can determine which | |
353 | mechanism is the default for your target by compiling a testcase that | |
354 | uses exceptions and doing an 'nm' on the object file; if it uses __throw, | |
355 | it's using the first mechanism. If it uses __sjthrow, it's using the | |
356 | second. | |
357 | ||
358 | You can turn EH support off with -fno-exceptions. | |
1e60a96e | 359 | |
405a745b JM |
360 | * RTTI support has been rewritten to work properly and is now on by default. |
361 | This means code that uses virtual functions will have a modest space | |
362 | overhead. You can use the -fno-rtti flag to disable RTTI support. | |
1e60a96e JM |
363 | |
364 | * On ELF systems, duplicate copies of symbols with 'initialized common' | |
365 | linkage (such as template instantiations, vtables, and extern inlines) | |
366 | will now be discarded by the GNU linker, so you don't need to use -frepo. | |
367 | This support requires GNU ld from binutils 2.8 or later. | |
5c825fc2 | 368 | |
405a745b JM |
369 | * The overload resolution code has been rewritten to conform to the latest |
370 | C++ Working Paper. Built-in operators are now considered as candidates | |
371 | in operator overload resolution. Function template overloading chooses | |
372 | the more specialized template, and handles base classes in type deduction | |
373 | and guiding declarations properly. In this release the old code can | |
374 | still be selected with -fno-ansi-overloading, although this is not | |
375 | supported and will be removed in a future release. | |
376 | ||
377 | * Standard usage syntax for the std namespace is supported; std is treated | |
378 | as an alias for global scope. General namespaces are still not supported. | |
3041f77a | 379 | |
1e60a96e JM |
380 | * New flags: |
381 | ||
19754d4c JM |
382 | + New warning -Wno-pmf-conversion (don't warn about |
383 | converting from a bound member function pointer to function | |
384 | pointer). | |
1e60a96e JM |
385 | |
386 | + A flag -Weffc++ has been added for violations of some of the style | |
387 | guidelines in Scott Meyers' _Effective C++_ books. | |
388 | ||
389 | + -Woverloaded-virtual now warns if a virtual function in a base | |
390 | class is hidden in a derived class, rather than warning about | |
391 | virtual functions being overloaded (even if all of the inherited | |
392 | signatures are overridden) as it did before. | |
393 | ||
394 | + -Wall no longer implies -W. The new warning flag, -Wsign-compare, | |
395 | included in -Wall, warns about dangerous comparisons of signed and | |
396 | unsigned values. Only the flag is new; it was previously part of | |
397 | -W. | |
398 | ||
399 | + The new flag, -fno-weak, disables the use of weak symbols. | |
8eeda2ec | 400 | |
405a745b JM |
401 | * Synthesized methods are now emitted in any translation units that need |
402 | an out-of-line copy. They are no longer affected by #pragma interface | |
403 | or #pragma implementation. | |
404 | ||
405 | * __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the | |
406 | parser; previously they were treated as string constants. So code like | |
407 | `printf (__FUNCTION__ ": foo")' must be rewritten to | |
408 | `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. | |
409 | ||
8eeda2ec JM |
410 | * local static variables in extern inline functions will be shared between |
411 | translation units. | |
412 | ||
8eeda2ec | 413 | * -fvtable-thunks is supported for all targets, and is the default for |
1e60a96e | 414 | Linux with glibc 2.x (also called libc 6.x). |
8eeda2ec | 415 | |
fb52f6de JM |
416 | * bool is now always the same size as another built-in type. Previously, |
417 | a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a | |
418 | 64-bit bool. This should only affect Irix 6, which was not supported in | |
419 | 2.7.2. | |
420 | ||
421 | * new (nothrow) is now supported. | |
422 | ||
fb52f6de JM |
423 | * Synthesized destructors are no longer made virtual just because the class |
424 | already has virtual functions, only if they override a virtual destructor | |
425 | in a base class. The compiler will warn if this affects your code. | |
426 | ||
8e69329a | 427 | * The g++ driver now only links against libstdc++, not libg++; it is |
fb52f6de JM |
428 | functionally identical to the c++ driver. |
429 | ||
430 | * (void *)0 is no longer considered a null pointer constant; NULL in | |
431 | <stddef.h> is now defined as __null, a magic constant of type (void *) | |
432 | normally, or (size_t) with -ansi. | |
433 | ||
fb52f6de JM |
434 | * The name of a class is now implicitly declared in its own scope; A::A |
435 | refers to A. | |
436 | ||
e1467ff2 | 437 | * Local classes are now supported. |
fb52f6de | 438 | |
fb52f6de JM |
439 | * __attribute__ can now be attached to types as well as declarations. |
440 | ||
fb52f6de JM |
441 | * The compiler no longer emits a warning if an ellipsis is used as a |
442 | function's argument list. | |
443 | ||
fb52f6de | 444 | * Definition of nested types outside of their containing class is now |
405a745b | 445 | supported. For instance: |
fb52f6de JM |
446 | |
447 | struct A { | |
448 | struct B; | |
449 | B* bp; | |
450 | }; | |
451 | ||
452 | struct A::B { | |
453 | int member; | |
454 | }; | |
455 | ||
fb52f6de JM |
456 | * On the HPPA, some classes that do not define a copy constructor |
457 | will be passed and returned in memory again so that functions | |
458 | returning those types can be inlined. | |
386b8a85 JM |
459 | |
460 | *** The g++ team thanks everyone that contributed to this release, | |
461 | but especially: | |
462 | ||
463 | * Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. | |
464 | * Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. | |
465 | * Jason Merrill <jason@cygnus.com>, the g++ maintainer. | |
466 | * Mark Mitchell <mmitchell@usa.net>, who implemented member function | |
467 | templates and explicit qualification of function templates. | |
468 | * Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of | |
469 | the exception handling work. |