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