NEWS revision 50397
1*** Changes in EGCS 1.1: 2 3* Namespaces are fully supported. The library has not yet been converted 4 to use namespace std, however, and the old std-faking code is still on by 5 default. To turn it off, you can use -fhonor-std. 6 7* Massive template improvements: 8 + member template classes are supported. 9 + template friends are supported. 10 + template template parameters are supported. 11 + local classes in templates are supported. 12 + lots of bugs fixed. 13 14* operator new now throws bad_alloc where appropriate. 15 16* Exception handling is now thread safe, and supports nested exceptions and 17 placement delete. Exception handling overhead on x86 is much lower with 18 GNU as 2.9. 19 20* protected virtual inheritance is now supported. 21 22* Loops are optimized better; we now move the test to the end in most 23 cases, like the C frontend does. 24 25* For class D derived from B which has a member 'int i', &D::i is now of 26 type 'int B::*' instead of 'int D::*'. 27 28* An _experimental_ new ABI for g++ can be turned on with -fnew-abi. The 29 current features of this are more efficient allocation of base classes 30 (including the empty base optimization), and more compact mangling of C++ 31 symbol names (which can be turned on separately with -fsquangle). This 32 ABI is subject to change without notice, so don't use it for anything 33 that you don't want to rebuild with every release of the compiler. 34 35 As with all ABI-changing flags, this flag is for experts only, as all 36 code (including the library code in libgcc and libstdc++) must be 37 compiled with the same ABI. 38 39*** Changes in EGCS 1.0: 40 41* A public review copy of the December 1996 Draft of the ISO/ANSI C++ 42 standard is now available. See 43 44 http://www.cygnus.com/misc/wp/ 45 46 for more information. 47 48* g++ now uses a new implementation of templates. The basic idea is that 49 now templates are minimally parsed when seen and then expanded later. 50 This allows conformant early name binding and instantiation controls, 51 since instantiations no longer have to go through the parser. 52 53 What you get: 54 55 + Inlining of template functions works without any extra effort or 56 modifications. 57 + Instantiations of class templates and methods defined in the class 58 body are deferred until they are actually needed (unless 59 -fexternal-templates is specified). 60 + Nested types in class templates work. 61 + Static data member templates work. 62 + Member function templates are now supported. 63 + Partial specialization of class templates is now supported. 64 + Explicit specification of template parameters to function templates 65 is now supported. 66 67 Things you may need to fix in your code: 68 69 + Syntax errors in templates that are never instantiated will now be 70 diagnosed. 71 + Types and class templates used in templates must be declared 72 first, or the compiler will assume they are not types, and fail. 73 + Similarly, nested types of template type parameters must be tagged 74 with the 'typename' keyword, except in base lists. In many cases, 75 but not all, the compiler will tell you where you need to add 76 'typename'. For more information, see 77 78 http://www.cygnus.com/misc/wp/dec96pub/template.html#temp.res 79 80 + Guiding declarations are no longer supported. Function declarations, 81 including friend declarations, do not refer to template instantiations. 82 You can restore the old behavior with -fguiding-decls until you fix 83 your code. 84 85 Other features: 86 87 + Default function arguments in templates will not be evaluated (or 88 checked for semantic validity) unless they are needed. Default 89 arguments in class bodies will not be parsed until the class 90 definition is complete. 91 + The -ftemplate-depth-NN flag can be used to increase the maximum 92 recursive template instantiation depth, which defaults to 17. If you 93 need to use this flag, the compiler will tell you. 94 + Explicit instantiation of template constructors and destructors is 95 now supported. For instance: 96 97 template A<int>::A(const A&); 98 99 Still not supported: 100 101 + Member class templates. 102 + Template friends. 103 104* Exception handling support has been significantly improved and is on by 105 default. The compiler supports two mechanisms for walking back up the 106 call stack; one relies on static information about how registers are 107 saved, and causes no runtime overhead for code that does not throw 108 exceptions. The other mechanism uses setjmp and longjmp equivalents, and 109 can result in quite a bit of runtime overhead. You can determine which 110 mechanism is the default for your target by compiling a testcase that 111 uses exceptions and doing an 'nm' on the object file; if it uses __throw, 112 it's using the first mechanism. If it uses __sjthrow, it's using the 113 second. 114 115 You can turn EH support off with -fno-exceptions. 116 117* RTTI support has been rewritten to work properly and is now on by default. 118 This means code that uses virtual functions will have a modest space 119 overhead. You can use the -fno-rtti flag to disable RTTI support. 120 121* On ELF systems, duplicate copies of symbols with 'initialized common' 122 linkage (such as template instantiations, vtables, and extern inlines) 123 will now be discarded by the GNU linker, so you don't need to use -frepo. 124 This support requires GNU ld from binutils 2.8 or later. 125 126* The overload resolution code has been rewritten to conform to the latest 127 C++ Working Paper. Built-in operators are now considered as candidates 128 in operator overload resolution. Function template overloading chooses 129 the more specialized template, and handles base classes in type deduction 130 and guiding declarations properly. In this release the old code can 131 still be selected with -fno-ansi-overloading, although this is not 132 supported and will be removed in a future release. 133 134* Standard usage syntax for the std namespace is supported; std is treated 135 as an alias for global scope. General namespaces are still not supported. 136 137* New flags: 138 139 + New warning -Wno-pmf-conversion (don't warn about 140 converting from a bound member function pointer to function 141 pointer). 142 143 + A flag -Weffc++ has been added for violations of some of the style 144 guidelines in Scott Meyers' _Effective C++_ books. 145 146 + -Woverloaded-virtual now warns if a virtual function in a base 147 class is hidden in a derived class, rather than warning about 148 virtual functions being overloaded (even if all of the inherited 149 signatures are overridden) as it did before. 150 151 + -Wall no longer implies -W. The new warning flag, -Wsign-compare, 152 included in -Wall, warns about dangerous comparisons of signed and 153 unsigned values. Only the flag is new; it was previously part of 154 -W. 155 156 + The new flag, -fno-weak, disables the use of weak symbols. 157 158* Synthesized methods are now emitted in any translation units that need 159 an out-of-line copy. They are no longer affected by #pragma interface 160 or #pragma implementation. 161 162* __FUNCTION__ and __PRETTY_FUNCTION__ are now treated as variables by the 163 parser; previously they were treated as string constants. So code like 164 `printf (__FUNCTION__ ": foo")' must be rewritten to 165 `printf ("%s: foo", __FUNCTION__)'. This is necessary for templates. 166 167* local static variables in extern inline functions will be shared between 168 translation units. 169 170* -fvtable-thunks is supported for all targets, and is the default for 171 Linux with glibc 2.x (also called libc 6.x). 172 173* bool is now always the same size as another built-in type. Previously, 174 a 64-bit RISC target using a 32-bit ABI would have 32-bit pointers and a 175 64-bit bool. This should only affect Irix 6, which was not supported in 176 2.7.2. 177 178* new (nothrow) is now supported. 179 180* Synthesized destructors are no longer made virtual just because the class 181 already has virtual functions, only if they override a virtual destructor 182 in a base class. The compiler will warn if this affects your code. 183 184* The g++ driver now only links against libstdc++, not libg++; it is 185 functionally identical to the c++ driver. 186 187* (void *)0 is no longer considered a null pointer constant; NULL in 188 <stddef.h> is now defined as __null, a magic constant of type (void *) 189 normally, or (size_t) with -ansi. 190 191* The name of a class is now implicitly declared in its own scope; A::A 192 refers to A. 193 194* Local classes are now supported. 195 196* __attribute__ can now be attached to types as well as declarations. 197 198* The compiler no longer emits a warning if an ellipsis is used as a 199 function's argument list. 200 201* Definition of nested types outside of their containing class is now 202 supported. For instance: 203 204 struct A { 205 struct B; 206 B* bp; 207 }; 208 209 struct A::B { 210 int member; 211 }; 212 213* On the HPPA, some classes that do not define a copy constructor 214 will be passed and returned in memory again so that functions 215 returning those types can be inlined. 216 217*** The g++ team thanks everyone that contributed to this release, 218 but especially: 219 220* Joe Buck <jbuck@synopsys.com>, the maintainer of the g++ FAQ. 221* Brendan Kehoe <brendan@cygnus.com>, who coordinates testing of g++. 222* Jason Merrill <jason@cygnus.com>, the g++ maintainer. 223* Mark Mitchell <mmitchell@usa.net>, who implemented member function 224 templates and explicit qualification of function templates. 225* Mike Stump <mrs@wrs.com>, the previous g++ maintainer, who did most of 226 the exception handling work. 227