NEWS revision 90075
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 changed to correctly handle this code: 8 9 struct A { 10 void operator delete[] (void *, size_t); 11 }; 12 13 struct B : public A { 14 }; 15 16 new B[10]; 17 18 The amount of storage allocated for the array will be greater than 19 it was in 3.0, in order to store the number of elements in the 20 array, so that the correct size can be passed to `operator delete[]' 21 when the array is deleted. Previously, the value passed to 22 `operator delete[]' was unpredictable. 23 24 This change will only affect code that declares a two-argument 25 `operator delete[]' with a second parameter of type `size_t' 26 in a base class, and does not override that definition in a 27 derived class. 28 29* The C++ ABI has been changed so that: 30 31 struct A { 32 void operator delete[] (void *, size_t); 33 void operator delete[] (void *); 34 }; 35 36 does not cause unnecessary storage to be allocated when an array of 37 `A' objects is allocated. 38 39 This change will only affect code that declares both of these 40 forms of `operator delete[]', and declared the two-argument form 41 before the one-argument form. 42 43* The C++ ABI has been changed so that when a parameter is passed by value, 44 any cleanup for that parameter is performed in the caller, as specified 45 by the ia64 C++ ABI, rather than the called function as before. 46 47*** Changes in GCC 3.0: 48 49* Support for guiding declarations has been removed. 50 51* G++ now supports importing member functions from base classes with a 52 using-declaration. 53 54* G++ now enforces access control for nested types. 55 56* In some obscure cases, functions with the same type could have the 57 same mangled name. This bug caused compiler crashes, link-time clashes, 58 and debugger crashes. Fixing this bug required breaking ABI 59 compatibility for the functions involved. The functions in questions 60 are those whose types involve non-type template arguments whose 61 mangled representations require more than one digit. 62 63* Support for assignment to `this' has been removed. This idiom 64 was used in the very early days of C++, before users were allowed 65 to overload `operator new'; it is no longer allowed by the C++ 66 standard. 67 68* Support for signatures, a G++ extension, have been removed. 69 70* Certain invalid conversions that were previously accepted will now 71 be rejected. For example, assigning function pointers of one type 72 to function pointers of another type now requires a cast, whereas 73 previously g++ would sometimes accept the code even without the 74 cast. 75 76* G++ previously allowed `sizeof (X::Y)' where Y was a non-static 77 member of X, even if the `sizeof' expression occurred outside 78 of a non-static member function of X (or one of its derived classes, 79 or a member-initializer for X or one of its derived classes.) This 80 extension has been removed. 81 82* G++ no longer allows you to overload the conditional operator (i.e., 83 the `?:' operator.) 84 85* The "named return value" extension: 86 87 int f () return r { r = 3; } 88 89 has been deprecated, and will be removed in a future version of G++. 90 91*** Changes in GCC 2.95: 92 93* Messages about non-conformant code that we can still handle ("pedwarns") 94 are now errors by default, rather than warnings. This can be reverted 95 with -fpermissive, and is overridden by -pedantic or -pedantic-errors. 96 97* String constants are now of type `const char[n]', rather than `char[n]'. 98 This can be reverted with -fno-const-strings. 99 100* References to functions are now supported. 101 102* Lookup of class members during class definition now works in all cases. 103 104* In overload resolution, type conversion operators are now properly 105 treated as always coming from the most derived class. 106 107* C9x-style restricted pointers are supported, using the `__restrict' 108 keyword. 109 110* You can now use -fno-implicit-inline-templates to suppress writing out 111 implicit instantiations of inline templates. Normally we do write them 112 out, even with -fno-implicit-templates, so that optimization doesn't 113 affect which instantiations are needed. 114 115* -fstrict-prototype now also suppresses implicit declarations. 116 117* Many obsolete options have been removed: -fall-virtual, -fmemoize-lookups, 118 -fsave-memoized, +e?, -fenum-int-equivalence, -fno-nonnull-objects. 119 120* Unused virtual functions can be discarded on some targets by specifying 121 -ffunction-sections -fvtable-gc to the compiler and --gc-sections to the 122 linker. Unfortunately, this only works on Linux if you're linking 123 statically. 124 125* Lots of bugs stomped. 126 127*** Changes in EGCS 1.1: 128 129* Namespaces are fully supported. The library has not yet been converted 130 to use namespace std, however, and the old std-faking code is still on by 131 default. To turn it off, you can use -fhonor-std. 132 133* Massive template improvements: 134 + member template classes are supported. 135 + template friends are supported. 136 + template template parameters are supported. 137 + local classes in templates are supported. 138 + lots of bugs fixed. 139 140* operator new now throws bad_alloc where appropriate. 141 142* Exception handling is now thread safe, and supports nested exceptions and 143 placement delete. Exception handling overhead on x86 is much lower with 144 GNU as 2.9. 145 146* protected virtual inheritance is now supported. 147 148* Loops are optimized better; we now move the test to the end in most 149 cases, like the C frontend does. 150 151* For class D derived from B which has a member 'int i', &D::i is now of 152 type 'int B::*' instead of 'int D::*'. 153 154* An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The 155 current features of this are more efficient allocation of base classes 156 (including the empty base optimization), and more compact mangling of C++ 157 symbol names (which can be turned on separately with -fsquangle). This 158 ABI is subject to change without notice, so don't use it for anything 159 that you don't want to rebuild with every release of the compiler. 160 161 As with all ABI-changing flags, this flag is for experts only, as all 162 code (including the library code in libgcc and libstdc++) must be 163 compiled with the same ABI. 164 165*** Changes in EGCS 1.0: 166 167* A public review copy of the December 1996 Draft of the ISO/ANSI C++ 168 standard is now available. See 169 170 http://www.cygnus.com/misc/wp/ 171 172 for more information. 173 174* g++ now uses a new implementation of templates. The basic idea is that 175 now templates are minimally parsed when seen and then expanded later. 176 This allows conformant early name binding and instantiation controls, 177 since instantiations no longer have to go through the parser. 178 179 What you get: 180 181 + Inlining of template functions works without any extra effort or 182 modifications. 183 + Instantiations of class templates and methods defined in the class 184 body are deferred until they are actually needed (unless 185 -fexternal-templates is specified). 186 + Nested types in class templates work. 187 + Static data member templates work. 188 + Member function templates are now supported. 189 + Partial specialization of class templates is now supported. 190 + Explicit specification of template parameters to function templates 191 is now supported. 192 193 Things you may need to fix in your code: 194 195 + Syntax errors in templates that are never instantiated will now be 196 diagnosed. 197 + Types and class templates used in templates must be declared 198 first, or the compiler will assume they are not types, and fail. 199 + Similarly, nested types of template type parameters must be tagged 200 with the 'typename' keyword, except in base lists. In many cases, 201 but not all, the compiler will tell you where you need to add 202 'typename'. For more information, see 203 204 http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res 205 206 + Guiding declarations are no longer supported. Function declarations, 207 including friend declarations, do not refer to template instantiations. 208 You can restore the old behavior with -fguiding-decls until you fix 209 your code. 210 211 Other features: 212 213 + Default function arguments in templates will not be evaluated (or 214 checked for semantic validity) unless they are needed. Default 215 arguments in class bodies will not be parsed until the class 216 definition is complete. 217 + The -ftemplate-depth-NN flag can be used to increase the maximum 218 recursive template instantiation depth, which defaults to 17. If you 219 need to use this flag, the compiler will tell you. 220 + Explicit instantiation of template constructors and destructors is 221 now supported. For instance: 222 223 template A<int>::A(const A&); 224 225 Still not supported: 226 227 + Member class templates. 228 + Template friends. 229 230* Exception handling support has been significantly improved and is on by 231 default. The compiler supports two mechanisms for walking back up the 232 call stack; one relies on static information about how registers are 233 saved, and causes no runtime overhead for code that does not throw 234 exceptions. The other mechanism uses setjmp and longjmp equivalents, and 235 can result in quite a bit of runtime overhead. You can determine which 236 mechanism is the default for your target by compiling a testcase that 237 uses exceptions and doing an 'nm' on the object file; if it uses __throw, 238 it's using the first mechanism. If it uses __sjthrow, it's using the 239 second. 240 241 You can turn EH support off with -fno-exceptions. 242 243* RTTI support has been rewritten to work properly and is now on by default. 244 This means code that uses virtual functions will have a modest space 245 overhead. You can use the -fno-rtti flag to disable RTTI support. 246 247* On ELF systems, duplicate copies of symbols with 'initialized common' 248 linkage (such as template instantiations, vtables, and extern inlines) 249 will now be discarded by the GNU linker, so you don't need to use -frepo. 250 This support requires GNU ld from binutils 2.8 or later. 251 252* The overload resolution code has been rewritten to conform to the latest 253 C++ Working Paper. Built-in operators are now considered as candidates 254 in operator overload resolution. Function template overloading chooses 255 the more specialized template, and handles base classes in type deduction 256 and guiding declarations properly. In this release the old code can 257 still be selected with -fno-ansi-overloading, although this is not 258 supported and will be removed in a future release. 259 260* Standard usage syntax for the std namespace is supported; std is treated 261 as an alias for global scope. General namespaces are still not supported. 262 263* New flags: 264 265 + New warning -Wno-pmf-conversion (don't warn about 266 converting from a bound member function pointer to function 267 pointer). 268 269 + A flag -Weffc++ has been added for violations of some of the style 270 guidelines in Scott Meyers' _Effective C++_ books. 271 272 + -Woverloaded-virtual now warns if a virtual function in a base 273 class is hidden in a derived class, rather than warning about 274 virtual functions being overloaded (even if all of the inherited 275 signatures are overridden) as it did before. 276 277 + -Wall no longer implies -W. The new warning flag, -Wsign-compare, 278 included in -Wall, warns about dangerous comparisons of signed and 279 unsigned values. Only the flag is new; it was previously part of 280 -W. 281 282 + The new flag, -fno-weak, disables the use of weak symbols. 283 284* Synthesized methods are now emitted in any translation units that need 285 an out-of-line copy. They are no longer affected by #pragma interface 286 or #pragma implementation. 287 288* __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the 289 parser; previously they were treated as string constants. So code like 290 `printf (__FUNCTION__ ": foo")' must be rewritten to 291 `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. 292 293* local static variables in extern inline functions will be shared between 294 translation units. 295 296* -fvtable-thunks is supported for all targets, and is the default for 297 Linux with glibc 2.x (also called libc 6.x). 298 299* bool is now always the same size as another built-in type. Previously, 300 a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a 301 64-bit bool. This should only affect Irix 6, which was not supported in 302 2.7.2. 303 304* new (nothrow) is now supported. 305 306* Synthesized destructors are no longer made virtual just because the class 307 already has virtual functions, only if they override a virtual destructor 308 in a base class. The compiler will warn if this affects your code. 309 310* The g++ driver now only links against libstdc++, not libg++; it is 311 functionally identical to the c++ driver. 312 313* (void *)0 is no longer considered a null pointer constant; NULL in 314 <stddef.h> is now defined as __null, a magic constant of type (void *) 315 normally, or (size_t) with -ansi. 316 317* The name of a class is now implicitly declared in its own scope; A::A 318 refers to A. 319 320* Local classes are now supported. 321 322* __attribute__ can now be attached to types as well as declarations. 323 324* The compiler no longer emits a warning if an ellipsis is used as a 325 function's argument list. 326 327* Definition of nested types outside of their containing class is now 328 supported. For instance: 329 330 struct A { 331 struct B; 332 B* bp; 333 }; 334 335 struct A::B { 336 int member; 337 }; 338 339* On the HPPA, some classes that do not define a copy constructor 340 will be passed and returned in memory again so that functions 341 returning those types can be inlined. 342 343*** The g++ team thanks everyone that contributed to this release, 344 but especially: 345 346* Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. 347* Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. 348* Jason Merrill <jason@cygnus.com>, the g++ maintainer. 349* Mark Mitchell <mmitchell@usa.net>, who implemented member function 350 templates and explicit qualification of function templates. 351* Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of 352 the exception handling work. 353