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-% File: porting.texi
-% Author: Mark Mitchell
-% Date: 11/21/2000
-%
-% Contents:
-%
-% Copyright (c) 2000 by CodeSourcery, LLC. All rights reserved.
-%
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\input texinfo
@c ---------------------------------------------------------------------
This file explains how to port libstdc++-v3 (the GNU C++ library) to
a new target.
-Copyright (c) 2000 Free Software Foundation, Inc.
+Copyright (c) 2000, 2001 Free Software Foundation, Inc.
@end ifinfo
@c ---------------------------------------------------------------------
@author Mark Mitchell
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 2000 Free Software Foundation, Inc.
+Copyright @copyright{} 2000, 2001 Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'', the Front-Cover
+texts being (a) (see below), and with the Back-Cover Texts being (b)
+(see below). A copy of the license is included in the section entitled
+``GNU Free Documentation License''.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
@end titlepage
@c ---------------------------------------------------------------------
* Operating system:: Configuring for your operating system.
* Character types:: Implementing character classification.
* Thread safety:: Implementing atomic operations.
+* Numeric limits:: Implementing numeric limits.
* Libtool:: Using libtool.
+* GNU Free Documentation License:: How you can copy and share this manual.
@end menu
@c ---------------------------------------------------------------------
header file that defines @code{off_t}, or the other types; you simply
have to provide the macros.
-In addition, several libstdc++-v3 source files unconditionally define the macro
-@code{_POSIX_SOURCE}. On many systems, defining this macro causes large
-portions of the C library header files to be eliminated at preprocessing
-time. Therefore, you may have to @code{#undef} this macro, or define
-other macros (like @code{_LARGEFILE_SOURCE} or @code{__EXTENSIONS__}).
-You won't know what macros to define or undefine at this point; you'll
-have to try compiling the library and seeing what goes wrong. If you
-see errors about calling functions that have not been declared, look in
-your C library headers to see if the functions are declared there, and
-then figure out what macros you should but in @file{bits/os_defines.h}
-to make these declarations available.
+In addition, several libstdc++-v3 source files unconditionally define
+the macro @code{_POSIX_SOURCE}. On many systems, defining this macro
+causes large portions of the C library header files to be eliminated
+at preprocessing time. Therefore, you may have to @code{#undef} this
+macro, or define other macros (like @code{_LARGEFILE_SOURCE} or
+@code{__EXTENSIONS__}). You won't know what macros to define or
+undefine at this point; you'll have to try compiling the library and
+seeing what goes wrong. If you see errors about calling functions
+that have not been declared, look in your C library headers to see if
+the functions are declared there, and then figure out what macros you
+need to define. You will need to add them to the
+@code{CPLUSPLUS_CPP_SPEC} macro in the GCC configuration file for your
+target. It will not work to simply define these macros in
+@file{os_defines.h}.
+
+At this time, there are two libstdc++-v3-specific macros which may be
+defined. @code{_G_USING_THUNKS} may be defined to 0 to express that the
+port doesn't use thunks (although it is unclear that this is still
+useful since libio support isn't currently working and the g++ v3 ABI
+invalidates the assumption that some ports don't use thunks).
+@code{_GLIBCPP_AVOID_FSEEK} may be defined if seeking on an interactive
+stream (or one hooked to a pipe) is not allowed by the OS. In this
+case, getc()/ungetc() will be used at some key locations in the library
+implementation instead of fseek(). Currently, the code path to avoid
+fseek() is only enabled when the seek size is 1 character away from the
+current stream position. This is known to improve *-unknown-freebsd*
+and sparc-sun-solaris2.*.
Finally, you should bracket the entire file in an include-guard, like
this:
@end example
@c ---------------------------------------------------------------------
+@c Numeric limits
+@c ---------------------------------------------------------------------
+
+@node Numeric limits
+@chapter Numeric limits
+
+The C++ library requires information about the fundamental data types,
+such as the minimum and maximum representable values of each type.
+You can define each of these values individually, but it is usually
+easiest just to indicate how many bits are used in each of the data
+types and let the library do the rest. For information about the
+macros to define, see the top of @file{include/bits/std_limits.h}.
+
+If you need to define any macros, you can do so in
+@file{os_defines.h}. However, if all operating systems for your CPU
+are likely to use the same values, you can provide a CPU-specific file
+instead so that you do not have to provide the same definitions for
+each operating system. To take that approach, create a new file
+called @file{limits.h} in your CPU configuration directory (e.g.,
+@file{config/cpu/i386/bits}) and then modify @file{configure.target}
+so that @code{LIMITSH} is set to the CPU directory (e.g.,
+@file{config/cpu/i386}). Note that @code{LIMITSH} should not include
+the @samp{bits} part of the directory name.
+
+@c ---------------------------------------------------------------------
@c Libtool
@c ---------------------------------------------------------------------
@node Libtool
@chapter Libtool
-The C++ library is linked with libtool. Explaining the full workings of
-libtool is beyond the scope of this document, but there is one
-particular bit that should be explained here. The C++ run-time library
-contains initialization code that needs to be run as the library is
-loaded. Often, that requires linking in special object files when the
-C++ library is built as a shared library, or taking other
-system-specific actions.
+The C++ library is compiled, archived and linked with libtool.
+Explaining the full workings of libtool is beyond the scope of this
+document, but there are a few, particular bits that are necessary for
+porting.
+
+Some parts of the libstdc++-v3 library are compiled with the libtool
+@code{--tags CXX} option (the C++ definitions for libtool). Therefore,
+@file{ltcf-cxx.sh} in the top-level directory needs to have the correct
+logic to compile and archive objects equivalent to the C version of libtool,
+@file{ltcf-c.sh}. Some libtool targets have definitions for C but not
+for C++, or C++ definitions which have not been kept up to date.
+
+The C++ run-time library contains initialization code that needs to be
+run as the library is loaded. Often, that requires linking in special
+object files when the C++ library is built as a shared library, or
+taking other system-specific actions.
The libstdc++-v3 library is linked with the C version of libtool, even though it
is a C++ library. Therefore, the C version of libtool needs to ensure
operating system.
@c ---------------------------------------------------------------------
+@c GFDL
+@c ---------------------------------------------------------------------
+
+@include fdl.texi
+
+@c ---------------------------------------------------------------------
@c Epilogue
@c ---------------------------------------------------------------------
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