Noteworthy changes in GCC for EGCS. The -specs=file switch allows you to override default specs used in invoking programs like cc1, as, etc. Options -Wall and -Wimplicit now cause GCC to warn about implicit int in declarations (e.g. `register i;'), since the C Standard committee has decided to disallow this in the next revision of the standard. The following new targets are supported: Solaris 2.5 running on UltraSPARC's. The sparclet cpu (a.out file format). Solaris 2.51 running on PowerPC's. Linux running on PowerPC's. Embedded target m32r-elf. New features for the Hitachi H8/300(H). -malign-300 -ms The -ms switch generates code for the Hitachi H8/S processor. New features for SPARC-based systems: -mcpu=xxx -mtune=xxx -mimpure-text and -mno-impure-text New features for all rs6000 and PowerPC systems: -mcpu=604e -mcpu=801 -mcpu=823 -mtune=xxx -mupdate -mno-update -mfused-madd -mno-fused-madd New features for PowerPC-based systems running either System V, Linux, Solaris, or embedded systems: -mregnames -meabi -mcall-linux -mcall-solaris -mcall-sysv-eabi -mcall-sysv-noeabi -msdata -msdata=none -msdata=default -msdata=sysv -msdata=eabi -memb -msim -mmvme wchar_t is now of type long, not unsigned short as per ABI. -p/-pg support -mcpu=403 now implies -mstrict-align. Options -mno-v8 and -mno-sparclite are no longer supported on SPARC targets. Options -mcypress, -mv8, -msupersparc, -msparclite, -mf930, and -mf934 are deprecated and will be deleted in GCC 2.9. Use -mcpu=xxx instead. GCC on the PA requires either gas-2.7 or the HP assembler; for best results using GAS is highly recommended. GAS is required for -g and exception handling support. Aix 4.1 GCC targets now default to -mcpu=common so that programs compiled can be moved between rs6000 and powerpc based systems. A consequence of this is that -static won't work, and that some programs may be slightly slower. You can select the default value to use for -mcpu=xxx on rs6000 and powerpc targets by using the --with-cpu=xxx option when confiuring the compiler. In addition, a new options, -mtune=xxx was added that selects the machine to schedule for but does not select the architecture level. Directory names used for storing the multilib libraries on System V and embedded PowerPC systems have been shortened to work with commands like tar that have fixed limits on pathname size. Noteworthy changes in GCC version 2.7.2: A few bugs have been fixed (most notably the generation of an invalid assembler opcode on some RS/6000 systems). Noteworthy changes in GCC version 2.7.1: This release fixes numerous bugs (mostly minor) in GCC 2.7.0, but also contains a few new features, mostly related to specific targets. Major changes have been made in code to support Windows NT. The following new targets are supported: 2.9 BSD on PDP-11 Linux on m68k HP/UX version 10 on HP PA RISC (treated like version 9) DEC Alpha running Windows NT When parsing C, GCC now recognizes C++ style `//' comments unless you specify `-ansi' or `-traditional'. The PowerPC System V targets (powerpc-*-sysv, powerpc-*-eabi) now use the calling sequence specified in the System V Application Binary Interface Processor Supplement (PowerPC Processor ABI Supplement) rather than the calling sequence used in GCC version 2.7.0. That calling sequence was based on the AIX calling sequence without function descriptors. To compile code for that older calling sequence, either configure the compiler for powerpc-*-eabiaix or use the -mcall-aix switch when compiling and linking. Noteworthy changes in GCC version 2.7.0: GCC now works better on systems that use ".obj" and ".exe" instead of ".o" and no extension. This involved changes to the driver program, gcc.c, to convert ".o" names to ".obj" and to GCC's Makefile to use ".obj" and ".exe" in filenames that are not targets. In order to build GCC on such systems, you may need versions of GNU make and/or compatible shells. At this point, this support is preliminary. Object file extensions of ".obj" and executable file extensions of ".exe" are allowed when using appropriate version of GNU Make. Numerous enhancements were made to the __attribute__ facility including more attributes and more places that support it. We now support the "packed", "nocommon", "noreturn", "volatile", "const", "unused", "transparent_union", "constructor", "destructor", "mode", "section", "align", "format", "weak", and "alias" attributes. Each of these names may also be specified with added underscores, e.g., "__packed__". __attribute__ may now be applied to parameter definitions, function definitions, and structure, enum, and union definitions. GCC now supports returning more structures in registers, as specified by many calling sequences (ABIs), such as on the HP PA RISC. A new option '-fpack-struct' was added to automatically pack all structure members together without holes. There is a new library (cpplib) and program (cppmain) that at some point will replace cpp (aka cccp). To use cppmain as cpp now, pass the option CCCP=cppmain to make. The library is already used by the fix-header program, which should speed up the fixproto script. New options for supported targets: GNU on many targets. NetBSD on MIPS, m68k, VAX, and x86. LynxOS on x86, m68k, Sparc, and RS/6000. VxWorks on many targets. Windows/NT on x86 architecture. Initial support for Windows/NT on Alpha (not fully working). Many embedded targets, specifically UDI on a29k, aout, coff, elf, and vsta "operating systems" on m68k, m88k, mips, sparc, and x86. Additional support for x86 (i386, i486, and Pentium): Work with old and new linkers for Linux-based GNU systems, supporting both a.out and ELF. FreeBSD on x86. Stdcall convention. -malign-double, -mregparm=, -malign-loops= and -malign-jumps= switches. On ISC systems, support -Xp like -posix. Additions for RS/6000: Instruction scheduling information for PowerPC 403. AIX 4.1 on PowerPC. -mstring and -mno-string. -msoft-float and floating-point emulation included. Preliminary support for PowerPC System V.4 with or without the GNU as. Preliminary support for EABI. Preliminary support for 64-bit systems. Both big and little endian systems. New features for MIPS-based systems: r4650. mips4 and R8000. Irix 6.0. 64-bit ABI. Allow dollar signs in labels on SGI/Irix 5.x. New support for HP PA RISC: Generation of PIC (requires binutils-2.5.2.u6 or later). HP-UX version 9 on HP PA RISC (dynamically links even with -g). Processor variants for HP PA RISC: 700, 7100, and 7100LC. Automatic generation of long calls when needed. -mfast-indirect-calls for kernels and static binaries. The called routine now copies arguments passed by invisible reference, as required by the calling standard. Other new miscellaneous target-specific support: -mno-multm on a29k. -mold-align for i960. Configuration for "semi-hosted" ARM. -momit-leaf-frame-pointer for M88k. SH3 variant of Hitachi Super-H and support both big and little endian. Changes to Objective-C: Bare-bones implementation of NXConstantString has been added, which is invoked by the @"string" directive. Class * has been changed to Class to conform to the NextSTEP and OpenStep runtime. Enhancements to make dynamic loading easier. The module version number has been updated to Version 7, thus existing code will need to be recompiled to use the current run-time library. GCC now supports the ISO Normative Addendum 1 to the C Standard. As a result: The header defines macros for C programs written in national variants of ISO 646. The following digraph tokens are supported: <: :> <% %> %: %:%: These behave like the following, respectively: [ ] { } # ## Digraph tokens are supported unless you specify the `-traditional' option; you do not need to specify `-ansi' or `-trigraphs'. Except for contrived and unlikely examples involving preprocessor stringizing, digraph interpretation doesn't change the meaning of programs; this is unlike trigraph interpretation, which changes the meanings of relatively common strings. The macro __STDC_VERSION__ has the value 199409L. As usual, for full conformance to the standard, you also need a C library that conforms. The following lists changes that have been made to g++. If some features mentioned below sound unfamiliar, you will probably want to look at the recently-released public review copy of the C++ Working Paper. For PostScript and PDF (Adobe Acrobat) versions, see the archive at ftp://research.att.com/dist/stdc++/WP. For HTML and ASCII versions, see ftp://ftp.cygnus.com/pub/g++. On the web, see http://www.cygnus.com/~mrs/wp-draft. The scope of variables declared in the for-init-statement has been changed to conform to http://www.cygnus.com/~mrs/wp-draft/stmt.html#stmt.for; as a result, packages such as groff 1.09 will not compile unless you specify the -fno-for-scope flag. PLEASE DO NOT REPORT THIS AS A BUG; this is a change mandated by the C++ standardization committee. Binary incompatibilities: The builtin 'bool' type is now the size of a machine word on RISC targets, for code efficiency; it remains one byte long on CISC targets. Code that does not use #pragma interface/implementation will most likely shrink dramatically, as g++ now only emits the vtable for a class in the translation unit where its first non-inline, non-abstract virtual function is defined. Classes that do not define the copy constructor will sometimes be passed and returned in registers. This may illuminate latent bugs in your code. Support for automatic template instantiation has *NOT* been added, due to a disagreement over design philosophies. Support for exception handling has been improved; more targets are now supported, and throws will use the RTTI mechanism to match against the catch parameter type. Optimization is NOT SUPPORTED with -fhandle-exceptions; no need to report this as a bug. Support for Run-Time Type Identification has been added with -frtti. This support is still in alpha; one major restriction is that any file compiled with -frtti must include . Preliminary support for namespaces has been added. This support is far from complete, and probably not useful. Synthesis of compiler-generated constructors, destructors and assignment operators is now deferred until the functions are used. The parsing of expressions such as `a ? b : c = 1' has changed from `(a ? b : c) = 1' to `a : b ? (c = 1)'. The code generated for testing conditions, especially those using || and &&, is now more efficient. The operator keywords and, and_eq, bitand, bitor, compl, not, not_eq, or, or_eq, xor and xor_eq are now supported. Use -ansi or -foperator-names to enable them. The 'explicit' keyword is now supported. 'explicit' is used to mark constructors and type conversion operators that should not be used implicitly. g++ now accepts the typename keyword, though it currently has no semantics; it can be a no-op in the current template implementation. You may want to start using it in your code, however, since the pending rewrite of the template implementation to compile STL properly (perhaps for 2.8.0, perhaps not) will require you to use it as indicated by the current draft. Handling of user-defined type conversion has been overhauled so that type conversion operators are now found and used properly in expressions and function calls. -fno-strict-prototype now only applies to function declarations with "C" linkage. g++ now warns about 'if (x=0)' with -Wparentheses or -Wall. #pragma weak and #pragma pack are supported on System V R4 targets, as are various other target-specific #pragmas supported by gcc. new and delete of const types is now allowed (with no additional semantics). Explicit instantiation of template methods is now supported. Also, 'inline template class foo;' can be used to emit only the vtable for a template class. With -fcheck-new, g++ will check the return value of all calls to operator new, and not attempt to modify a returned null pointer. The template instantiation code now handles more conversions when passing to a parameter that does not depend on template arguments. This means that code like 'string s; cout << s;' now works. Invalid jumps in a switch statement past declarations that require initializations are now caught. Functions declared 'extern inline' now have the same linkage semantics as inline member functions. On supported targets, where previously these functions (and vtables, and template instantiations) would have been defined statically, they will now be defined as weak symbols so that only one out-of-line definition is used. collect2 now demangles linker output, and c++filt has become part of the gcc distribution. Noteworthy changes in GCC version 2.6.3: A few more bugs have been fixed. Noteworthy changes in GCC version 2.6.2: A few bugs have been fixed. Names of attributes can now be preceded and followed by double underscores. Noteworthy changes in GCC version 2.6.1: Numerous (mostly minor) bugs have been fixed. The following new configurations are supported: GNU on x86 (instead of treating it like MACH) NetBSD on Sparc and Motorola 68k AIX 4.1 on RS/6000 and PowerPC systems Sequent DYNUX/ptx 1.x and 2.x. Both COFF and ELF configurations on AViiON without using /bin/gcc Windows/NT on x86 architecture; preliminary AT&T DSP1610 digital signal processor chips i960 systems on bare boards using COFF PDP11; target only and not extensively tested The -pg option is now supported for Alpha under OSF/1 V3.0 or later. Files with an extension of ".c++" are treated as C++ code. The -Xlinker and -Wl arguments are now passed to the linker in the position they were specified on the command line. This makes it possible, for example, to pass flags to the linker about specific object files. The use of positional arguments to the configure script is no longer recommended. Use --target= to specify the target; see the GCC manual. The 386 now supports two new switches: -mreg-alloc= changes the default register allocation order used by the compiler, and -mno-wide-multiply disables the use of the mul/imul instructions that produce 64 bit results in EAX:EDX from 32 bit operands to do long long multiplies and 32-bit division by constants. Noteworthy changes in GCC version 2.6.0: Numerous bugs have been fixed, in the C and C++ front-ends, as well as in the common compiler code. This release includes the C, Objective-C, and C++ compilers. However, we have moved the files for the C++ compiler (G++) files to a subdirectory, cp. Subsequent releases of GCC will split these files to a separate TAR file. The G++ team has been tracking the development of the ANSI standard for C++. Here are some new features added from the latest working paper: * built-in boolean type 'bool', with constants 'true' and 'false'. * array new and delete (operator new [] and delete []). * WP-conforming lifetime of temporaries. * explicit instantiation of templates (template class A;), along with an option (-fno-implicit-templates) to disable emission of implicitly instantiated templates, obsoletes -fexternal-templates. * static member constants (static const int foo = 4; within the class declaration). Many error messages have been improved to tell the user more about the problem. Conformance checking with -pedantic-errors has been improved. G++ now compiles Fresco. There is now an experimental implementation of virtual functions using thunks instead of Cfront-style vtables, enabled with -fvtable-thunks. This option also enables a heuristic which causes the compiler to only emit the vtable in the translation unit where its first non-inline virtual function is defined; using this option and -fno-implicit-templates, users should be able to avoid #pragma interface/implementation altogether. Signatures have been added as a GNU C++ extension. Using the option -fhandle-signatures, users are able to turn on recognition of signatures. A short introduction on signatures is in the section `Extension to the C++ Language' in the manual. The `g++' program is now a C program, rather than a shell script. Lots and lots and lots of bugs fixes, in nested types, access control, pointers to member functions, the parser, templates, overload resolution, etc, etc. There have been two major enhancements to the Objective-C compiler: 1) Added portability. It now runs on Alpha, and some problems with message forwarding have been addressed on other platforms. 2) Selectors have been redefined to be pointers to structs like: { void *sel_id, char *sel_types }, where the sel_id is the unique identifier, the selector itself is no longer unique. Programmers should use the new function sel_eq to test selector equivalence. The following major changes have been made to the base compiler and machine-specific files. - The MIL-STD-1750A is a new port, but still preliminary. - The h8/300h is now supported; both the h8/300 and h8/300h ports come with 32 bit IEEE 754 software floating point support. - The 64-bit Sparc (v9) and 64-bit MIPS chips are supported. - NetBSD is supported on m68k, Intel x86, and pc523 systems and FreeBSD on x86. - COFF is supported on x86, m68k, and Sparc systems running LynxOS. - 68K systems from Bull and Concurrent are supported and System V Release 4 is supported on the Atari. - GCC supports GAS on the Motorola 3300 (sysV68) and debugging (assuming GAS) on the Plexus 68K system. (However, GAS does not yet work on those systems). - System V Release 4 is supported on MIPS (Tandem). - For DG/UX, an ELF configuration is now supported, and both the ELF and BCS configurations support ELF and COFF object file formats. - OSF/1 V2.0 is supported on Alpha. - Function profiling is also supported on Alpha. - GAS and GDB is supported for Irix 5 (MIPS). - "common mode" (code that will run on both POWER and PowerPC architectures) is now supported for the RS/6000 family; the compiler knows about more PPC chips. - Both NeXTStep 2.1 and 3 are supported on 68k-based architectures. - On the AMD 29k, the -msoft-float is now supported, as well as -mno-sum-in-toc for RS/6000, -mapp-regs and -mflat for Sparc, and -membedded-pic for MIPS. - GCC can now convert division by integer constants into the equivalent multiplication and shift operations when that is faster than the division. - Two new warning options, -Wbad-function-cast and -Wmissing-declarations have been added. - Configurations may now add machine-specific __attribute__ options on type; many machines support the `section' attribute. - The -ffast-math flag permits some optimization that violate strict IEEE rules, such as converting X * 0.0 to 0.0. Noteworthy changes in GCC version 2.5.8: This release only fixes a few serious bugs. These include fixes for a bug that prevented most programs from working on the RS/6000, a bug that caused invalid assembler code for programs with a `switch' statement on the NS32K, a G++ problem that caused undefined names in some configurations, and several less serious problems, some of which can affect most configuration. Noteworthy change in GCC version 2.5.7: This release only fixes a few bugs, one of which was causing bootstrap compare errors on some systems. Noteworthy change in GCC version 2.5.6: A few backend bugs have been fixed, some of which only occur on one machine. The C++ compiler in 2.5.6 includes: * fixes for some common crashes * correct handling of nested types that are referenced as `foo::bar' * spurious warnings about friends being declared static and never defined should no longer appear * enums that are local to a method in a class, or a class that's local to a function, are now handled correctly. For example: class foo { void bar () { enum { x, y } E; x; } }; void bar () { class foo { enum { x, y } E; E baz; }; } Noteworthy change in GCC version 2.5.5: A large number of C++ bugs have been fixed. The fixproto script adds prototypes conditionally on __cplusplus. Noteworthy change in GCC version 2.5.4: A bug fix in passing of structure arguments for the HP-PA architecture makes code compiled with GCC 2.5.4 incompatible with code compiled with earlier versions (if it passes struct arguments of 33 to 64 bits, interspersed with other types of arguments). Noteworthy change in gcc version 2.5.3: The method of "mangling" C++ function names has been changed. So you must recompile all C++ programs completely when you start using GCC 2.5. Also, GCC 2.5 requires libg++ version 2.5. Earlier libg++ versions won't work with GCC 2.5. (This is generally true--GCC version M.N requires libg++ version M.N.) Noteworthy GCC changes in version 2.5: * There is now support for the IBM 370 architecture as a target. Currently the only operating system supported is MVS; GCC does not run on MVS, so you must produce .s files using GCC as a cross compiler, then transfer them to MVS to assemble them. This port is not reliable yet. * The Power PC is now supported. * The i860-based Paragon machine is now supported. * The Hitachi 3050 (an HP-PA machine) is now supported. * The variable __GNUC_MINOR__ holds the minor version number of GCC, as an integer. For version 2.5.X, the value is 5. * In C, initializers for static and global variables are now processed an element at a time, so that they don't need a lot of storage. * The C syntax for specifying which structure field comes next in an initializer is now `.FIELDNAME='. The corresponding syntax for array initializers is now `[INDEX]='. For example, char whitespace[256] = { [' '] = 1, ['\t'] = 1, ['\n'] = 1 }; This was changed to accord with the syntax proposed by the Numerical C Extensions Group (NCEG). * Complex numbers are now supported in C. Use the keyword __complex__ to declare complex data types. See the manual for details. * GCC now supports `long double' meaningfully on the Sparc (128-bit floating point) and on the 386 (96-bit floating point). The Sparc support is enabled on on Solaris 2.x because earlier system versions (SunOS 4) have bugs in the emulation. * All targets now have assertions for cpu, machine and system. So you can now use assertions to distinguish among all supported targets. * Nested functions in C may now be inline. Just declare them inline in the usual way. * Packed structure members are now supported fully; it should be possible to access them on any supported target, no matter how little alignment they have. * To declare that a function does not return, you must now write something like this (works only in 2.5): void fatal () __attribute__ ((noreturn)); or like this (works in older versions too): typedef void voidfn (); volatile voidfn fatal; It used to be possible to do so by writing this: volatile void fatal (); but it turns out that ANSI C requires that to mean something else (which is useless). Likewise, to declare that a function is side-effect-free so that calls may be deleted or combined, write something like this (works only in 2.5): int computation () __attribute__ ((const)); or like this (works in older versions too): typedef int intfn (); const intfn computation; * The new option -iwithprefixbefore specifies a directory to add to the search path for include files in the same position where -I would put it, but uses the specified prefix just like -iwithprefix. * Basic block profiling has been enhanced to record the function the basic block comes from, and if the module was compiled for debugging, the line number and filename. A default version of the basic block support module has been added to libgcc2 that appends the basic block information to a text file 'bb.out'. Machine descriptions can now override the basic block support module in the target macro file. New features in g++: * The new flag `-fansi-overloading' for C++. Use a newly implemented scheme of argument matching for C++. It makes g++ more accurately obey the rules set down in Chapter 13 of the Annotated C++ Reference Manual (the ARM). This option will be turned on by default in a future release. * The -finline-debug flag is now gone (it was never really used by the compiler). * Recognizing the syntax for pointers to members, e.g., "foo::*bar", has been dramatically improved. You should not get any syntax errors or incorrect runtime results while using pointers to members correctly; if you do, it's a definite bug. * Forward declaration of an enum is now flagged as an error. * Class-local typedefs are now working properly. * Nested class support has been significantly improved. The compiler will now (in theory) support up to 240 nested classes before hitting other system limits (like memory size). * There is a new C version of the `g++' driver, to replace the old shell script. This should significantly improve the performance of executing g++ on a system where a user's PATH environment variable references many NFS-mounted filesystems. This driver also works under MS-DOS and OS/2. * The ANSI committee working on the C++ standard has adopted a new keyword `mutable'. This will allow you to make a specific member be modifiable in an otherwise const class. Noteworthy GCC changes in version 2.4.4: A crash building g++ on various hosts (including m68k) has been fixed. Also the g++ compiler no longer reports incorrect ambiguities in some situations where they do not exist, and const template member functions are now being found properly. Noteworthy GCC changes in version 2.4: * On each target, the default is now to return short structures compatibly with the "usual" compiler on that target. For most targets, this means the default is to return all structures in memory, like long structures, in whatever way is used on that target. Use -freg-struct-return to enable returning short structures (and unions) in registers. This change means that newly compiled binaries are incompatible with binaries compiled with previous versions of GCC. On some targets, GCC is itself the usual compiler. On these targets, the default way to return short structures is still in registers. Use -fpcc-struct-return to tell GCC to return them in memory. * There is now a floating point emulator which can imitate the way all supported target machines do floating point arithmetic. This makes it possible to have cross compilation to and from the VAX, and between machines of different endianness. However, this works only when the target machine description is updated to use the new facilities, and not all have been updated. This also makes possible support for longer floating point types. GCC 2.4 supports extended format on the 68K if you use `long double', for targets that have a 68881. (When we have run time library routines for extended floating point, then `long double' will use extended format on all 68K targets.) We expect to support extended floating point on the i386 and Sparc in future versions. * Building GCC now automatically fixes the system's header files. This should require no attention. * GCC now installs an unsigned data type as size_t when it fixes the header files (on all but a handful of old target machines). Therefore, the bug that size_t failed to be unsigned is fixed. * Building and installation are now completely separate. All new files are constructed during the build process; installation just copies them. * New targets supported: Clipper, Hitachi SH, Hitachi 8300, and Sparc Lite. * A totally new and much better Objective C run time system is included. * Objective C supports many new features. Alas, I can't describe them since I don't use that language; however, they are the same ones supported in recent versions of the NeXT operating system. * The builtin functions __builtin_apply_args, __builtin_apply and __builtin_return let you record the arguments and returned value of a function without knowing their number or type. * The builtin string variables __FUNCTION__ and __PRETTY_FUNCTION__ give the name of the function in the source, and a pretty-printed version of the name. The two are the same in C, but differ in C++. * Casts to union types do not yield lvalues. * ## before an empty rest argument discards the preceding sequence of non-whitespace characters from the macro definition. (This feature is subject to change.) New features specific to C++: * The manual contains a new section ``Common Misunderstandings with GNU C++'' that C++ users should read. * #pragma interface and #pragma implementation let you use the same C++ source file for both interface and implementation. However, this mechanism is still in transition. * Named returned values let you avoid an extra constructor call when a function result has a class type. * The C++ operators ? yield min and max, respectively. * C++ gotos can exit a block safely even if the block has aggregates that require destructors. * gcc defines the macro __GNUG__ when compiling C++ programs. * GNU C++ now correctly distinguishes between the prefix and postfix forms of overloaded operator ++ and --. To avoid breaking old code, if a class defines only the prefix form, the compiler accepts either ++obj or obj++, unless -pedantic is used. * If you are using version 2.3 of libg++, you need to rebuild it with `make CC=gcc' to avoid mismatches in the definition of `size_t'. Newly documented compiler options: -fnostartfiles Omit the standard system startup files when linking. -fvolatile-global Consider memory references to extern and global data items to be volatile. -idirafter DIR Add DIR to the second include path. -iprefix PREFIX Specify PREFIX for later -iwithprefix options. -iwithprefix DIR Add PREFIX/DIR to the second include path. -mv8 Emit Sparc v8 code (with integer multiply and divide). -msparclite Emit Sparclite code (roughly v7.5). -print-libgcc-file-name Search for the libgcc.a file, print its absolute file name, and exit. -Woverloaded-virtual Warn when a derived class function declaration may be an error in defining a C++ virtual function. -Wtemplate-debugging When using templates in a C++ program, warn if debugging is not yet fully available. +eN Control how C++ virtual function definitions are used (like cfront 1.x).