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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 | ||
cd65f082 NS |
43 | * Default arguments in function types have been deprecated and will be |
44 | removed. | |
45 | ||
a723baf1 MM |
46 | * G++ used to accept code like this: |
47 | ||
48 | struct S { | |
49 | int h(); | |
50 | void f(int i = g()); | |
51 | int g(int i = h()); | |
52 | }; | |
53 | ||
54 | This behavior is not mandated by the standard. | |
55 | ||
56 | Now G++ issues an error about this code. To avoid the error, you must | |
57 | move the declaration of `g' before the declaration of `f'. The | |
58 | default arguments for `g' must be visible at the point where it is | |
59 | called. | |
60 | ||
61 | * When -pedantic is used, G++ now issues errors about spurious semicolons; | |
62 | for example: | |
63 | ||
64 | namespace N {}; // Invalid semicolon. | |
65 | void f() {}; // Invalid semicolon. | |
66 | ||
67 | * G++ no longer accepts attributes for a declarator after the | |
68 | initializer associated with that declarator. For example: | |
69 | ||
70 | X x(1) __attribute__((...)); | |
71 | ||
72 | is no longer accepted. Instead, use: | |
73 | ||
74 | X x __attribute__((...)) (1); | |
75 | ||
75e74c71 NS |
76 | * Covariant returns are implemented for all but varadic functions that |
77 | require an adjustment. | |
78 | ||
8e3df2de MM |
79 | *** Changes in GCC 3.3: |
80 | ||
81 | * The "new X = 3" extension has been removed; you must now use "new X(3)". | |
82 | ||
dcba9b0f MM |
83 | * G++ no longer allows in-class initializations of static data members |
84 | that do not have arithmetic or enumeration type. For example: | |
85 | ||
86 | struct S { | |
87 | static const char* const p = "abc"; | |
88 | }; | |
89 | ||
90 | is no longer accepted. | |
91 | ||
92 | Use the standards-conformant form: | |
93 | ||
94 | struct S { | |
95 | static const char* const p; | |
96 | }; | |
97 | ||
98 | const char* const S::p = "abc"; | |
99 | ||
100 | instead. | |
101 | ||
102 | (ISO C++ is even stricter; it does not allow in-class | |
103 | initializations of floating-point types.) | |
104 | ||
e065a36e MM |
105 | *** Changes in GCC 3.1: |
106 | ||
1dbb6023 NS |
107 | * -fhonor-std and -fno-honor-std have been removed. -fno-honor-std was |
108 | a workaround to allow std compliant code to work with the non-std | |
109 | compliant libstdc++-v2. libstdc++-v3 is std compliant. | |
110 | ||
e61d6d83 JM |
111 | * The C++ ABI has been fixed so that `void (A::*)() const' is mangled as |
112 | "M1AKFvvE", rather than "MK1AFvvE" as before. This change only affects | |
113 | pointer to cv-qualified member function types. | |
114 | ||
dbc957f1 MM |
115 | * The C++ ABI has been changed to correctly handle this code: |
116 | ||
117 | struct A { | |
118 | void operator delete[] (void *, size_t); | |
119 | }; | |
120 | ||
121 | struct B : public A { | |
122 | }; | |
123 | ||
124 | new B[10]; | |
125 | ||
126 | The amount of storage allocated for the array will be greater than | |
127 | it was in 3.0, in order to store the number of elements in the | |
128 | array, so that the correct size can be passed to `operator delete[]' | |
129 | when the array is deleted. Previously, the value passed to | |
130 | `operator delete[]' was unpredictable. | |
131 | ||
132 | This change will only affect code that declares a two-argument | |
133 | `operator delete[]' with a second parameter of type `size_t' | |
134 | in a base class, and does not override that definition in a | |
135 | derived class. | |
136 | ||
137 | * The C++ ABI has been changed so that: | |
138 | ||
139 | struct A { | |
140 | void operator delete[] (void *, size_t); | |
141 | void operator delete[] (void *); | |
142 | }; | |
143 | ||
aba649ba | 144 | does not cause unnecessary storage to be allocated when an array of |
dbc957f1 MM |
145 | `A' objects is allocated. |
146 | ||
147 | This change will only affect code that declares both of these | |
148 | forms of `operator delete[]', and declared the two-argument form | |
149 | before the one-argument form. | |
150 | ||
f21add07 JM |
151 | * The C++ ABI has been changed so that when a parameter is passed by value, |
152 | any cleanup for that parameter is performed in the caller, as specified | |
fd70bb64 JM |
153 | by the ia64 C++ ABI, rather than the called function as before. As a |
154 | result, classes with a non-trivial destructor but a trivial copy | |
155 | constructor will be passed and returned by invisible reference, rather | |
156 | than by bitwise copy as before. | |
f21add07 | 157 | |
d6b2c474 JM |
158 | * G++ now supports the "named return value optimization": for code like |
159 | ||
160 | A f () { | |
161 | A a; | |
162 | ... | |
163 | return a; | |
164 | } | |
165 | ||
166 | G++ will allocate 'a' in the return value slot, so that the return | |
167 | becomes a no-op. For this to work, all return statements in the function | |
168 | must return the same variable. | |
169 | ||
e065a36e | 170 | *** Changes in GCC 3.0: |
9fe94fd3 | 171 | |
2228d450 MM |
172 | * Support for guiding declarations has been removed. |
173 | ||
9fe94fd3 JM |
174 | * G++ now supports importing member functions from base classes with a |
175 | using-declaration. | |
176 | ||
177 | * G++ now enforces access control for nested types. | |
5bb2f1e7 | 178 | |
858a0ff1 MM |
179 | * In some obscure cases, functions with the same type could have the |
180 | same mangled name. This bug caused compiler crashes, link-time clashes, | |
7ba0b0f7 | 181 | and debugger crashes. Fixing this bug required breaking ABI |
858a0ff1 MM |
182 | compatibility for the functions involved. The functions in questions |
183 | are those whose types involve non-type template arguments whose | |
184 | mangled representations require more than one digit. | |
185 | ||
9bfadf57 MM |
186 | * Support for assignment to `this' has been removed. This idiom |
187 | was used in the very early days of C++, before users were allowed | |
188 | to overload `operator new'; it is no longer allowed by the C++ | |
189 | standard. | |
190 | ||
cf7cf3d2 MM |
191 | * Support for signatures, a G++ extension, have been removed. |
192 | ||
5bb2f1e7 MM |
193 | * Certain invalid conversions that were previously accepted will now |
194 | be rejected. For example, assigning function pointers of one type | |
195 | to function pointers of another type now requires a cast, whereas | |
196 | previously g++ would sometimes accept the code even without the | |
197 | cast. | |
198 | ||
199 | * G++ previously allowed `sizeof (X::Y)' where Y was a non-static | |
200 | member of X, even if the `sizeof' expression occurred outside | |
201 | of a non-static member function of X (or one of its derived classes, | |
202 | or a member-initializer for X or one of its derived classes.) This | |
203 | extension has been removed. | |
204 | ||
205 | * G++ no longer allows you to overload the conditional operator (i.e., | |
206 | the `?:' operator.) | |
207 | ||
44835fdd MM |
208 | * The "named return value" extension: |
209 | ||
210 | int f () return r { r = 3; } | |
211 | ||
212 | has been deprecated, and will be removed in a future version of G++. | |
213 | ||
b1b9b120 | 214 | *** Changes in GCC 2.95: |
2642b9bf JM |
215 | |
216 | * Messages about non-conformant code that we can still handle ("pedwarns") | |
217 | are now errors by default, rather than warnings. This can be reverted | |
218 | with -fpermissive, and is overridden by -pedantic or -pedantic-errors. | |
219 | ||
b1b9b120 JM |
220 | * String constants are now of type `const char[n]', rather than `char[n]'. |
221 | This can be reverted with -fno-const-strings. | |
222 | ||
223 | * References to functions are now supported. | |
224 | ||
225 | * Lookup of class members during class definition now works in all cases. | |
226 | ||
227 | * In overload resolution, type conversion operators are now properly | |
228 | treated as always coming from the most derived class. | |
229 | ||
230 | * C9x-style restricted pointers are supported, using the `__restrict' | |
231 | keyword. | |
232 | ||
233 | * You can now use -fno-implicit-inline-templates to suppress writing out | |
234 | implicit instantiations of inline templates. Normally we do write them | |
235 | out, even with -fno-implicit-templates, so that optimization doesn't | |
236 | affect which instantiations are needed. | |
237 | ||
238 | * -fstrict-prototype now also suppresses implicit declarations. | |
239 | ||
240 | * Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups, | |
241 | -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects. | |
242 | ||
243 | * Unused virtual functions can be discarded on some targets by specifying | |
244 | -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the | |
245 | linker. Unfortunately, this only works on Linux if you're linking | |
246 | statically. | |
247 | ||
248 | * Lots of bugs stomped. | |
249 | ||
1a408d07 | 250 | *** Changes in EGCS 1.1: |
be343556 | 251 | |
d1fec180 JM |
252 | * Namespaces are fully supported. The library has not yet been converted |
253 | to use namespace std, however, and the old std-faking code is still on by | |
254 | default. To turn it off, you can use -fhonor-std. | |
255 | ||
570221c2 JM |
256 | * Massive template improvements: |
257 | + member template classes are supported. | |
258 | + template friends are supported. | |
259 | + template template parameters are supported. | |
260 | + local classes in templates are supported. | |
261 | + lots of bugs fixed. | |
be343556 JM |
262 | |
263 | * operator new now throws bad_alloc where appropriate. | |
264 | ||
d1fec180 JM |
265 | * Exception handling is now thread safe, and supports nested exceptions and |
266 | placement delete. Exception handling overhead on x86 is much lower with | |
267 | GNU as 2.9. | |
570221c2 JM |
268 | |
269 | * protected virtual inheritance is now supported. | |
270 | ||
271 | * Loops are optimized better; we now move the test to the end in most | |
272 | cases, like the C frontend does. | |
273 | ||
274 | * For class D derived from B which has a member 'int i', &D::i is now of | |
275 | type 'int B::*' instead of 'int D::*'. | |
276 | ||
d1fec180 JM |
277 | * An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The |
278 | current features of this are more efficient allocation of base classes | |
279 | (including the empty base optimization), and more compact mangling of C++ | |
280 | symbol names (which can be turned on separately with -fsquangle). This | |
281 | ABI is subject to change without notice, so don't use it for anything | |
282 | that you don't want to rebuild with every release of the compiler. | |
283 | ||
cb99b4a0 JM |
284 | As with all ABI-changing flags, this flag is for experts only, as all |
285 | code (including the library code in libgcc and libstdc++) must be | |
286 | compiled with the same ABI. | |
287 | ||
be343556 | 288 | *** Changes in EGCS 1.0: |
fb52f6de | 289 | |
19754d4c JM |
290 | * A public review copy of the December 1996 Draft of the ISO/ANSI C++ |
291 | standard is now available. See | |
fb52f6de JM |
292 | |
293 | http://www.cygnus.com/misc/wp/ | |
294 | ||
295 | for more information. | |
296 | ||
1e60a96e JM |
297 | * g++ now uses a new implementation of templates. The basic idea is that |
298 | now templates are minimally parsed when seen and then expanded later. | |
299 | This allows conformant early name binding and instantiation controls, | |
300 | since instantiations no longer have to go through the parser. | |
301 | ||
302 | What you get: | |
303 | ||
304 | + Inlining of template functions works without any extra effort or | |
305 | modifications. | |
1e60a96e JM |
306 | + Instantiations of class templates and methods defined in the class |
307 | body are deferred until they are actually needed (unless | |
308 | -fexternal-templates is specified). | |
1e60a96e | 309 | + Nested types in class templates work. |
1e60a96e | 310 | + Static data member templates work. |
1e60a96e | 311 | + Member function templates are now supported. |
1e60a96e | 312 | + Partial specialization of class templates is now supported. |
386b8a85 JM |
313 | + Explicit specification of template parameters to function templates |
314 | is now supported. | |
1e60a96e | 315 | |
405a745b | 316 | Things you may need to fix in your code: |
1e60a96e | 317 | |
405a745b JM |
318 | + Syntax errors in templates that are never instantiated will now be |
319 | diagnosed. | |
1e60a96e JM |
320 | + Types and class templates used in templates must be declared |
321 | first, or the compiler will assume they are not types, and fail. | |
1e60a96e | 322 | + Similarly, nested types of template type parameters must be tagged |
405a745b JM |
323 | with the 'typename' keyword, except in base lists. In many cases, |
324 | but not all, the compiler will tell you where you need to add | |
325 | 'typename'. For more information, see | |
1e60a96e | 326 | |
405a745b | 327 | http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res |
1e60a96e | 328 | |
386b8a85 JM |
329 | + Guiding declarations are no longer supported. Function declarations, |
330 | including friend declarations, do not refer to template instantiations. | |
331 | You can restore the old behavior with -fguiding-decls until you fix | |
332 | your code. | |
333 | ||
1e60a96e JM |
334 | Other features: |
335 | ||
336 | + Default function arguments in templates will not be evaluated (or | |
337 | checked for semantic validity) unless they are needed. Default | |
338 | arguments in class bodies will not be parsed until the class | |
339 | definition is complete. | |
1e60a96e | 340 | + The -ftemplate-depth-NN flag can be used to increase the maximum |
405a745b JM |
341 | recursive template instantiation depth, which defaults to 17. If you |
342 | need to use this flag, the compiler will tell you. | |
386b8a85 JM |
343 | + Explicit instantiation of template constructors and destructors is |
344 | now supported. For instance: | |
345 | ||
346 | template A<int>::A(const A&); | |
1e60a96e JM |
347 | |
348 | Still not supported: | |
349 | ||
405a745b | 350 | + Member class templates. |
405a745b | 351 | + Template friends. |
1e60a96e JM |
352 | |
353 | * Exception handling support has been significantly improved and is on by | |
19754d4c JM |
354 | default. The compiler supports two mechanisms for walking back up the |
355 | call stack; one relies on static information about how registers are | |
356 | saved, and causes no runtime overhead for code that does not throw | |
357 | exceptions. The other mechanism uses setjmp and longjmp equivalents, and | |
358 | can result in quite a bit of runtime overhead. You can determine which | |
359 | mechanism is the default for your target by compiling a testcase that | |
360 | uses exceptions and doing an 'nm' on the object file; if it uses __throw, | |
361 | it's using the first mechanism. If it uses __sjthrow, it's using the | |
362 | second. | |
363 | ||
364 | You can turn EH support off with -fno-exceptions. | |
1e60a96e | 365 | |
405a745b JM |
366 | * RTTI support has been rewritten to work properly and is now on by default. |
367 | This means code that uses virtual functions will have a modest space | |
368 | overhead. You can use the -fno-rtti flag to disable RTTI support. | |
1e60a96e JM |
369 | |
370 | * On ELF systems, duplicate copies of symbols with 'initialized common' | |
371 | linkage (such as template instantiations, vtables, and extern inlines) | |
372 | will now be discarded by the GNU linker, so you don't need to use -frepo. | |
373 | This support requires GNU ld from binutils 2.8 or later. | |
5c825fc2 | 374 | |
405a745b JM |
375 | * The overload resolution code has been rewritten to conform to the latest |
376 | C++ Working Paper. Built-in operators are now considered as candidates | |
377 | in operator overload resolution. Function template overloading chooses | |
378 | the more specialized template, and handles base classes in type deduction | |
379 | and guiding declarations properly. In this release the old code can | |
380 | still be selected with -fno-ansi-overloading, although this is not | |
381 | supported and will be removed in a future release. | |
382 | ||
383 | * Standard usage syntax for the std namespace is supported; std is treated | |
384 | as an alias for global scope. General namespaces are still not supported. | |
3041f77a | 385 | |
1e60a96e JM |
386 | * New flags: |
387 | ||
19754d4c JM |
388 | + New warning -Wno-pmf-conversion (don't warn about |
389 | converting from a bound member function pointer to function | |
390 | pointer). | |
1e60a96e JM |
391 | |
392 | + A flag -Weffc++ has been added for violations of some of the style | |
393 | guidelines in Scott Meyers' _Effective C++_ books. | |
394 | ||
395 | + -Woverloaded-virtual now warns if a virtual function in a base | |
396 | class is hidden in a derived class, rather than warning about | |
397 | virtual functions being overloaded (even if all of the inherited | |
398 | signatures are overridden) as it did before. | |
399 | ||
400 | + -Wall no longer implies -W. The new warning flag, -Wsign-compare, | |
401 | included in -Wall, warns about dangerous comparisons of signed and | |
402 | unsigned values. Only the flag is new; it was previously part of | |
403 | -W. | |
404 | ||
405 | + The new flag, -fno-weak, disables the use of weak symbols. | |
8eeda2ec | 406 | |
405a745b JM |
407 | * Synthesized methods are now emitted in any translation units that need |
408 | an out-of-line copy. They are no longer affected by #pragma interface | |
409 | or #pragma implementation. | |
410 | ||
411 | * __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the | |
412 | parser; previously they were treated as string constants. So code like | |
413 | `printf (__FUNCTION__ ": foo")' must be rewritten to | |
414 | `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. | |
415 | ||
8eeda2ec JM |
416 | * local static variables in extern inline functions will be shared between |
417 | translation units. | |
418 | ||
8eeda2ec | 419 | * -fvtable-thunks is supported for all targets, and is the default for |
1e60a96e | 420 | Linux with glibc 2.x (also called libc 6.x). |
8eeda2ec | 421 | |
fb52f6de JM |
422 | * bool is now always the same size as another built-in type. Previously, |
423 | a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a | |
424 | 64-bit bool. This should only affect Irix 6, which was not supported in | |
425 | 2.7.2. | |
426 | ||
427 | * new (nothrow) is now supported. | |
428 | ||
fb52f6de JM |
429 | * Synthesized destructors are no longer made virtual just because the class |
430 | already has virtual functions, only if they override a virtual destructor | |
431 | in a base class. The compiler will warn if this affects your code. | |
432 | ||
8e69329a | 433 | * The g++ driver now only links against libstdc++, not libg++; it is |
fb52f6de JM |
434 | functionally identical to the c++ driver. |
435 | ||
436 | * (void *)0 is no longer considered a null pointer constant; NULL in | |
437 | <stddef.h> is now defined as __null, a magic constant of type (void *) | |
438 | normally, or (size_t) with -ansi. | |
439 | ||
fb52f6de JM |
440 | * The name of a class is now implicitly declared in its own scope; A::A |
441 | refers to A. | |
442 | ||
e1467ff2 | 443 | * Local classes are now supported. |
fb52f6de | 444 | |
fb52f6de JM |
445 | * __attribute__ can now be attached to types as well as declarations. |
446 | ||
fb52f6de JM |
447 | * The compiler no longer emits a warning if an ellipsis is used as a |
448 | function's argument list. | |
449 | ||
fb52f6de | 450 | * Definition of nested types outside of their containing class is now |
405a745b | 451 | supported. For instance: |
fb52f6de JM |
452 | |
453 | struct A { | |
454 | struct B; | |
455 | B* bp; | |
456 | }; | |
457 | ||
458 | struct A::B { | |
459 | int member; | |
460 | }; | |
461 | ||
fb52f6de JM |
462 | * On the HPPA, some classes that do not define a copy constructor |
463 | will be passed and returned in memory again so that functions | |
464 | returning those types can be inlined. | |
386b8a85 JM |
465 | |
466 | *** The g++ team thanks everyone that contributed to this release, | |
467 | but especially: | |
468 | ||
469 | * Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. | |
470 | * Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. | |
471 | * Jason Merrill <jason@cygnus.com>, the g++ maintainer. | |
472 | * Mark Mitchell <mmitchell@usa.net>, who implemented member function | |
473 | templates and explicit qualification of function templates. | |
474 | * Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of | |
475 | the exception handling work. |