NEWS revision 96263
1*** Changes in GCC 3.1: 2 3* -fhonor-std and -fno-honor-std have been removed. -fno-honor-std was 4 a workaround to allow std compliant code to work with the non-std 5 compliant libstdc++-v2. libstdc++-v3 is std compliant. 6 7* The C++ ABI has been fixed so that `void (A::*)() const' is mangled as 8 "M1AKFvvE", rather than "MK1AFvvE" as before. This change only affects 9 pointer to cv-qualified member function types. 10 11* The C++ ABI has been changed to correctly handle this code: 12 13 struct A { 14 void operator delete[] (void *, size_t); 15 }; 16 17 struct B : public A { 18 }; 19 20 new B[10]; 21 22 The amount of storage allocated for the array will be greater than 23 it was in 3.0, in order to store the number of elements in the 24 array, so that the correct size can be passed to `operator delete[]' 25 when the array is deleted. Previously, the value passed to 26 `operator delete[]' was unpredictable. 27 28 This change will only affect code that declares a two-argument 29 `operator delete[]' with a second parameter of type `size_t' 30 in a base class, and does not override that definition in a 31 derived class. 32 33* The C++ ABI has been changed so that: 34 35 struct A { 36 void operator delete[] (void *, size_t); 37 void operator delete[] (void *); 38 }; 39 40 does not cause unnecessary storage to be allocated when an array of 41 `A' objects is allocated. 42 43 This change will only affect code that declares both of these 44 forms of `operator delete[]', and declared the two-argument form 45 before the one-argument form. 46 47* The C++ ABI has been changed so that when a parameter is passed by value, 48 any cleanup for that parameter is performed in the caller, as specified 49 by the ia64 C++ ABI, rather than the called function as before. As a 50 result, classes with a non-trivial destructor but a trivial copy 51 constructor will be passed and returned by invisible reference, rather 52 than by bitwise copy as before. 53 54* G++ now supports the "named return value optimization": for code like 55 56 A f () { 57 A a; 58 ... 59 return a; 60 } 61 62 G++ will allocate 'a' in the return value slot, so that the return 63 becomes a no-op. For this to work, all return statements in the function 64 must return the same variable. 65 66*** Changes in GCC 3.0: 67 68* Support for guiding declarations has been removed. 69 70* G++ now supports importing member functions from base classes with a 71 using-declaration. 72 73* G++ now enforces access control for nested types. 74 75* In some obscure cases, functions with the same type could have the 76 same mangled name. This bug caused compiler crashes, link-time clashes, 77 and debugger crashes. Fixing this bug required breaking ABI 78 compatibility for the functions involved. The functions in questions 79 are those whose types involve non-type template arguments whose 80 mangled representations require more than one digit. 81 82* Support for assignment to `this' has been removed. This idiom 83 was used in the very early days of C++, before users were allowed 84 to overload `operator new'; it is no longer allowed by the C++ 85 standard. 86 87* Support for signatures, a G++ extension, have been removed. 88 89* Certain invalid conversions that were previously accepted will now 90 be rejected. For example, assigning function pointers of one type 91 to function pointers of another type now requires a cast, whereas 92 previously g++ would sometimes accept the code even without the 93 cast. 94 95* G++ previously allowed `sizeof (X::Y)' where Y was a non-static 96 member of X, even if the `sizeof' expression occurred outside 97 of a non-static member function of X (or one of its derived classes, 98 or a member-initializer for X or one of its derived classes.) This 99 extension has been removed. 100 101* G++ no longer allows you to overload the conditional operator (i.e., 102 the `?:' operator.) 103 104* The "named return value" extension: 105 106 int f () return r { r = 3; } 107 108 has been deprecated, and will be removed in a future version of G++. 109 110*** Changes in GCC 2.95: 111 112* Messages about non-conformant code that we can still handle ("pedwarns") 113 are now errors by default, rather than warnings. This can be reverted 114 with -fpermissive, and is overridden by -pedantic or -pedantic-errors. 115 116* String constants are now of type `const char[n]', rather than `char[n]'. 117 This can be reverted with -fno-const-strings. 118 119* References to functions are now supported. 120 121* Lookup of class members during class definition now works in all cases. 122 123* In overload resolution, type conversion operators are now properly 124 treated as always coming from the most derived class. 125 126* C9x-style restricted pointers are supported, using the `__restrict' 127 keyword. 128 129* You can now use -fno-implicit-inline-templates to suppress writing out 130 implicit instantiations of inline templates. Normally we do write them 131 out, even with -fno-implicit-templates, so that optimization doesn't 132 affect which instantiations are needed. 133 134* -fstrict-prototype now also suppresses implicit declarations. 135 136* Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups, 137 -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects. 138 139* Unused virtual functions can be discarded on some targets by specifying 140 -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the 141 linker. Unfortunately, this only works on Linux if you're linking 142 statically. 143 144* Lots of bugs stomped. 145 146*** Changes in EGCS 1.1: 147 148* Namespaces are fully supported. The library has not yet been converted 149 to use namespace std, however, and the old std-faking code is still on by 150 default. To turn it off, you can use -fhonor-std. 151 152* Massive template improvements: 153 + member template classes are supported. 154 + template friends are supported. 155 + template template parameters are supported. 156 + local classes in templates are supported. 157 + lots of bugs fixed. 158 159* operator new now throws bad_alloc where appropriate. 160 161* Exception handling is now thread safe, and supports nested exceptions and 162 placement delete. Exception handling overhead on x86 is much lower with 163 GNU as 2.9. 164 165* protected virtual inheritance is now supported. 166 167* Loops are optimized better; we now move the test to the end in most 168 cases, like the C frontend does. 169 170* For class D derived from B which has a member 'int i', &D::i is now of 171 type 'int B::*' instead of 'int D::*'. 172 173* An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The 174 current features of this are more efficient allocation of base classes 175 (including the empty base optimization), and more compact mangling of C++ 176 symbol names (which can be turned on separately with -fsquangle). This 177 ABI is subject to change without notice, so don't use it for anything 178 that you don't want to rebuild with every release of the compiler. 179 180 As with all ABI-changing flags, this flag is for experts only, as all 181 code (including the library code in libgcc and libstdc++) must be 182 compiled with the same ABI. 183 184*** Changes in EGCS 1.0: 185 186* A public review copy of the December 1996 Draft of the ISO/ANSI C++ 187 standard is now available. See 188 189 http://www.cygnus.com/misc/wp/ 190 191 for more information. 192 193* g++ now uses a new implementation of templates. The basic idea is that 194 now templates are minimally parsed when seen and then expanded later. 195 This allows conformant early name binding and instantiation controls, 196 since instantiations no longer have to go through the parser. 197 198 What you get: 199 200 + Inlining of template functions works without any extra effort or 201 modifications. 202 + Instantiations of class templates and methods defined in the class 203 body are deferred until they are actually needed (unless 204 -fexternal-templates is specified). 205 + Nested types in class templates work. 206 + Static data member templates work. 207 + Member function templates are now supported. 208 + Partial specialization of class templates is now supported. 209 + Explicit specification of template parameters to function templates 210 is now supported. 211 212 Things you may need to fix in your code: 213 214 + Syntax errors in templates that are never instantiated will now be 215 diagnosed. 216 + Types and class templates used in templates must be declared 217 first, or the compiler will assume they are not types, and fail. 218 + Similarly, nested types of template type parameters must be tagged 219 with the 'typename' keyword, except in base lists. In many cases, 220 but not all, the compiler will tell you where you need to add 221 'typename'. For more information, see 222 223 http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res 224 225 + Guiding declarations are no longer supported. Function declarations, 226 including friend declarations, do not refer to template instantiations. 227 You can restore the old behavior with -fguiding-decls until you fix 228 your code. 229 230 Other features: 231 232 + Default function arguments in templates will not be evaluated (or 233 checked for semantic validity) unless they are needed. Default 234 arguments in class bodies will not be parsed until the class 235 definition is complete. 236 + The -ftemplate-depth-NN flag can be used to increase the maximum 237 recursive template instantiation depth, which defaults to 17. If you 238 need to use this flag, the compiler will tell you. 239 + Explicit instantiation of template constructors and destructors is 240 now supported. For instance: 241 242 template A<int>::A(const A&); 243 244 Still not supported: 245 246 + Member class templates. 247 + Template friends. 248 249* Exception handling support has been significantly improved and is on by 250 default. The compiler supports two mechanisms for walking back up the 251 call stack; one relies on static information about how registers are 252 saved, and causes no runtime overhead for code that does not throw 253 exceptions. The other mechanism uses setjmp and longjmp equivalents, and 254 can result in quite a bit of runtime overhead. You can determine which 255 mechanism is the default for your target by compiling a testcase that 256 uses exceptions and doing an 'nm' on the object file; if it uses __throw, 257 it's using the first mechanism. If it uses __sjthrow, it's using the 258 second. 259 260 You can turn EH support off with -fno-exceptions. 261 262* RTTI support has been rewritten to work properly and is now on by default. 263 This means code that uses virtual functions will have a modest space 264 overhead. You can use the -fno-rtti flag to disable RTTI support. 265 266* On ELF systems, duplicate copies of symbols with 'initialized common' 267 linkage (such as template instantiations, vtables, and extern inlines) 268 will now be discarded by the GNU linker, so you don't need to use -frepo. 269 This support requires GNU ld from binutils 2.8 or later. 270 271* The overload resolution code has been rewritten to conform to the latest 272 C++ Working Paper. Built-in operators are now considered as candidates 273 in operator overload resolution. Function template overloading chooses 274 the more specialized template, and handles base classes in type deduction 275 and guiding declarations properly. In this release the old code can 276 still be selected with -fno-ansi-overloading, although this is not 277 supported and will be removed in a future release. 278 279* Standard usage syntax for the std namespace is supported; std is treated 280 as an alias for global scope. General namespaces are still not supported. 281 282* New flags: 283 284 + New warning -Wno-pmf-conversion (don't warn about 285 converting from a bound member function pointer to function 286 pointer). 287 288 + A flag -Weffc++ has been added for violations of some of the style 289 guidelines in Scott Meyers' _Effective C++_ books. 290 291 + -Woverloaded-virtual now warns if a virtual function in a base 292 class is hidden in a derived class, rather than warning about 293 virtual functions being overloaded (even if all of the inherited 294 signatures are overridden) as it did before. 295 296 + -Wall no longer implies -W. The new warning flag, -Wsign-compare, 297 included in -Wall, warns about dangerous comparisons of signed and 298 unsigned values. Only the flag is new; it was previously part of 299 -W. 300 301 + The new flag, -fno-weak, disables the use of weak symbols. 302 303* Synthesized methods are now emitted in any translation units that need 304 an out-of-line copy. They are no longer affected by #pragma interface 305 or #pragma implementation. 306 307* __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the 308 parser; previously they were treated as string constants. So code like 309 `printf (__FUNCTION__ ": foo")' must be rewritten to 310 `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. 311 312* local static variables in extern inline functions will be shared between 313 translation units. 314 315* -fvtable-thunks is supported for all targets, and is the default for 316 Linux with glibc 2.x (also called libc 6.x). 317 318* bool is now always the same size as another built-in type. Previously, 319 a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a 320 64-bit bool. This should only affect Irix 6, which was not supported in 321 2.7.2. 322 323* new (nothrow) is now supported. 324 325* Synthesized destructors are no longer made virtual just because the class 326 already has virtual functions, only if they override a virtual destructor 327 in a base class. The compiler will warn if this affects your code. 328 329* The g++ driver now only links against libstdc++, not libg++; it is 330 functionally identical to the c++ driver. 331 332* (void *)0 is no longer considered a null pointer constant; NULL in 333 <stddef.h> is now defined as __null, a magic constant of type (void *) 334 normally, or (size_t) with -ansi. 335 336* The name of a class is now implicitly declared in its own scope; A::A 337 refers to A. 338 339* Local classes are now supported. 340 341* __attribute__ can now be attached to types as well as declarations. 342 343* The compiler no longer emits a warning if an ellipsis is used as a 344 function's argument list. 345 346* Definition of nested types outside of their containing class is now 347 supported. For instance: 348 349 struct A { 350 struct B; 351 B* bp; 352 }; 353 354 struct A::B { 355 int member; 356 }; 357 358* On the HPPA, some classes that do not define a copy constructor 359 will be passed and returned in memory again so that functions 360 returning those types can be inlined. 361 362*** The g++ team thanks everyone that contributed to this release, 363 but especially: 364 365* Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. 366* Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. 367* Jason Merrill <jason@cygnus.com>, the g++ maintainer. 368* Mark Mitchell <mmitchell@usa.net>, who implemented member function 369 templates and explicit qualification of function templates. 370* Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of 371 the exception handling work. 372