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