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jlechner |
README for GAS
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A number of things have changed since version 1 and the wonderful
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world of gas looks very different. There's still a lot of irrelevant
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garbage lying around that will be cleaned up in time. Documentation
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is scarce, as are logs of the changes made since the last gas release.
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My apologies, and I'll try to get something useful.
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Unpacking and Installation - Summary
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====================================
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See ../binutils/README.
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To build just the assembler, make the target all-gas.
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Documentation
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=============
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The GAS release includes texinfo source for its manual, which can be processed
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into `info' or `dvi' forms.
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The DVI form is suitable for printing or displaying; the commands for doing
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this vary from system to system. On many systems, `lpr -d' will print a DVI
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file. On others, you may need to run a program such as `dvips' to convert the
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DVI file into a form your system can print.
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If you wish to build the DVI file, you will need to have TeX installed on your
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system. You can rebuild it by typing:
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cd gas/doc
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make as.dvi
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The Info form is viewable with the GNU Emacs `info' subsystem, or the
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stand-alone `info' program, available as part of the GNU Texinfo distribution.
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To build the info files, you will need the `makeinfo' program. Type:
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cd gas/doc
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make info
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Specifying names for hosts and targets
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======================================
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The specifications used for hosts and targets in the `configure'
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script are based on a three-part naming scheme, but some short
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predefined aliases are also supported. The full naming scheme encodes
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three pieces of information in the following pattern:
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ARCHITECTURE-VENDOR-OS
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For example, you can use the alias `sun4' as a HOST argument or in a
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`--target=TARGET' option. The equivalent full name is
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`sparc-sun-sunos4'.
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The `configure' script accompanying GAS does not provide any query
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facility to list all supported host and target names or aliases.
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`configure' calls the Bourne shell script `config.sub' to map
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abbreviations to full names; you can read the script, if you wish, or
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you can use it to test your guesses on abbreviations--for example:
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% sh config.sub i386v
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i386-unknown-sysv
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% sh config.sub i786v
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Invalid configuration `i786v': machine `i786v' not recognized
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`configure' options
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===================
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Here is a summary of the `configure' options and arguments that are
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most often useful for building GAS. `configure' also has several other
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options not listed here.
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configure [--help]
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[--prefix=DIR]
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[--srcdir=PATH]
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[--host=HOST]
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[--target=TARGET]
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[--with-OPTION]
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[--enable-OPTION]
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You may introduce options with a single `-' rather than `--' if you
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prefer; but you may abbreviate option names if you use `--'.
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`--help'
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Print a summary of the options to `configure', and exit.
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`-prefix=DIR'
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Configure the source to install programs and files under directory
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`DIR'.
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`--srcdir=PATH'
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Look for the package's source code in directory DIR. Usually
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`configure' can determine that directory automatically.
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`--host=HOST'
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Configure GAS to run on the specified HOST. Normally the
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configure script can figure this out automatically.
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There is no convenient way to generate a list of all available
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hosts.
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`--target=TARGET'
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Configure GAS for cross-assembling programs for the specified
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TARGET. Without this option, GAS is configured to assemble .o files
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that run on the same machine (HOST) as GAS itself.
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There is no convenient way to generate a list of all available
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targets.
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`--enable-OPTION'
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These flags tell the program or library being configured to
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configure itself differently from the default for the specified
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host/target combination. See below for a list of `--enable'
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options recognized in the gas distribution.
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`configure' accepts other options, for compatibility with configuring
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other GNU tools recursively; but these are the only options that affect
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GAS or its supporting libraries.
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The `--enable' options recognized by software in the gas distribution are:
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`--enable-targets=...'
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This causes one or more specified configurations to be added to those for
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which BFD support is compiled. Currently gas cannot use any format other
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than its compiled-in default, so this option is not very useful.
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`--enable-bfd-assembler'
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This causes the assembler to use the new code being merged into it to use
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BFD data structures internally, and use BFD for writing object files.
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For most targets, this isn't supported yet. For most targets where it has
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been done, it's already the default. So generally you won't need to use
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this option.
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Compiler Support Hacks
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======================
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On a few targets, the assembler has been modified to support a feature
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that is potentially useful when assembling compiler output, but which
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may confuse assembly language programmers. If assembler encounters a
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.word pseudo-op of the form symbol1-symbol2 (the difference of two
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symbols), and the difference of those two symbols will not fit in 16
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bits, the assembler will create a branch around a long jump to
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symbol1, and insert this into the output directly before the next
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label: The .word will (instead of containing garbage, or giving an
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error message) contain (the address of the long jump)-symbol2. This
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allows the assembler to assemble jump tables that jump to locations
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very far away into code that works properly. If the next label is
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more than 32K away from the .word, you lose (silently); RMS claims
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this will never happen. If the -K option is given, you will get a
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warning message when this happens.
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REPORTING BUGS IN GAS
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=====================
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Bugs in gas should be reported to:
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bug-binutils@gnu.org.
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They may be cross-posted to gcc-bugs@gnu.org if they affect the use of
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gas with gcc. They should not be reported just to gcc-bugs, since not
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all of the maintainers read that list.
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See ../binutils/README for what we need in a bug report.
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