APDL Public Domain 1/APDL_PD1A.iso/program/c/gnu_c/docs/intro

Text File | 1996-03-15 | 7.2 KB | 182 lines

                Introduction to GNU C on the Acorn


0.      Introduction

This is a short introduction to the GNU C compiler, and assumes that
you have GCC 2.7.2 and DRLink already installed on your computer.
If you do not, details of where to get GCC are at the end of
this article. It is not an introduction to C programming, for that you
will have to get a text book on the language.

GCC is a large program that requires approximately 3Mb of disc space, and a
minimum of 3Mb of free RAM, though if you have a 2Mb machine it will run
under !Virtual, but with a few problems (see the !ReadMe file in the
distribution for details).

The GCC distribution contains all that is needed for writing C programs,
apart from a linker, but a PD linker called DRLink is freely available.


1.      Simple compilations

GCC follows the same conventions as Acorn C with C sources held in the
'c' directory, header files being held in the 'h' directory, and compiled
object being held in the 'o' directory.

For simple use, all that is needed is to start up a task window, ensure that
there is 3Mb or so in the wimpslot and to type something like

        gcc hello.c

This will compile, assemble and link the source 'hello.c' to produce an
executable called '!RunImage', which can be run immediately.

It is possible to compile several sources at one go, mixing C sources in
the same program, using a command line of

        gcc file1.c file2.c file3.c file4.c

Again, this will compile, assemble and link all the sources to produce the
'!RunImage' executable.

To compile to the object form, use the -c switch. i.e.

        gcc -c file.c

will compile and assemble 'file.c' to 'file.o'.

2.      Switches

This is a list of the simpler, standard switches for GCC

-c              compile and assemble the source to the object file
-S              compile the source to assembler code
-E              preprocess the source file
-o <file>       put the resulting output into <file>
-O              apply some optimisations to the output
-O2             apply full optimisation.
-O3        full optimisation and inline small functions as well.

There are some additional ARM specific switches.

  * -mapcs, -mapcs-frame
   target for ARM Procedure Call Standard stack frames.
  * -mpoke-function-name
   place the name of the current function before the start of the function
   to allow the post mortem debugger to print a readable backtrace.
   Using it's opposite will reduce code size by about 3.5%.
  * -mfpe
   prevents instruction scheduling of floating point instructions since it
   increases compile time and the benefits acheived make no difference through
   the FPE.
  * -mapcs-32
   target the APCS-32 bit standard. Condition flags are assumed to be corrupted
   by function calls in this mode.
  * -mapcs-stack-check
   provide explicit stack checking on entry to each function which allocates
   temporary variables on the stack.
  * -mapcs-strict
   make the compiler conform strictly to the APCS even in the cases where
   stack frames do not need to be set up.
  * -msoft-float
   cause the compile to assume all floating point instructions are missing
   (and there is no emulator either), therefore generating function calls
   instead.
  * -mhard-float
   the opposite of -msoft-float
  * -mshort-load-bytes, -mno-short-load-words
   if the MMU traps unaligned word accesses, shorts must be loaded
   byte-at-a-time so this flag should be set.

  RISC OS specific options

  * -munique-areas
   generate each function in its own individual code area giving the linker
   extra chance to remove unused functions from the resulting binary.
  * -mthrowback
   send errors to a text editor capable of receiving 'throwbacks'.
  * -mstubs
   compiles to target SharedCLibrary and tells the linker to link with
   stubs instead of UnixLib.
  * -munixlib
   tell the linker to target UnixLib instead of the SharedCLibrary
  * -mdepend
   Generate the file !Depend which contains a list of all the source
   files that the produced object depend on. This is intended for use
   with amu, which edit the makefile to include these after the
   '# Dynamic Dependencies' line.


3.      Obtaining GCC

GCC can be obtained from various FTP sites. Prime sites for latest uploads
are:
   Demon Internet Services: ftp://ftp.demon.co.uk/pub/archimedes/
   Hensa/micros: ftp://micros.hensa.ac.uk/micros/arch/riscos/

Please note that the ARM backend used to create this RISC OS port is
unavailable to the general public. As well as changing the backend in a
significant way, bugs and patches have been applied to the GCC system
independent sources making it a more involved process for porting. However,
anybody who is interested in the ARM/RISC OS backend for alternate compiler
ports using GCC can request it from me.

Main GCC sources can be obtained from the sites described below. Compiler
sources are approximately 7.5Mb compressed, 27Mb uncompressed.

DRLink can be obtained from Arcade BBS [phone], 8N1 or
I believe it is on Hensa/micros.

4.    Contacting me

I can generally be contacted at <[e-mail]> during
University term times and at <[e-mail]> outside
term times.

However, if neither of those addresses seem to get a reply, then I can
be contacted through Simon Callan at <[e-mail]>.


[ Most GNU software is packed using the GNU `gzip' compression program.
  Source code is available on most sites distributing GNU software.

  For information on how to order GNU software on tape, floppy or cd-rom, or
  printed GNU manuals, check the file etc/ORDERS in the GNU Emacs
  distribution, ftp the file /pub/gnu/GNUinfo/ORDERS on prep, or
  e-mail a request to: [e-mail]

  By ordering your GNU software from the FSF, you help us continue to
  develop more free software.  Media revenues are our primary source of
  support.  Donations to FSF are deductible on US tax returns.

  The above software will soon be at these ftp sites as well.
  Please try them before prep.ai.mit.edu as prep is very busy!

  thanx [e-mail]

        ASIA: ftp.cs.titech.ac.jp, utsun.s.u-tokyo.ac.jp:/ftpsync/prep,
  cair-archive.kaist.ac.kr:/pub/gnu, ftp.nectec.or.th:/pub/mirrors/gnu
        AUSTRALIA: archie.au:/gnu (archie.oz or archie.oz.au for ACSnet)
        AFRICA: ftp.sun.ac.za:/pub/gnu
        MIDDLE-EAST: ftp.technion.ac.il:/pub/unsupported/gnu
        EUROPE: irisa.irisa.fr:/pub/gnu, ftp.univ-lyon1.fr:pub/gnu,
  ftp.mcc.ac.uk, unix.hensa.ac.uk:/mirrors/uunet/systems/gnu,
  src.doc.ic.ac.uk:/gnu, ftp.ieunet.ie:pub/gnu, ftp.eunet.ch,
  nic.switch.ch:/mirror/gnu, ftp.informatik.rwth-aachen.de:/pub/gnu,
  ftp.informatik.tu-muenchen.de, ftp.win.tue.nl:/pub/gnu, ftp.nl.net,
  ftp.etsimo.uniovi.es:/pub/gnu ftp.funet.fi:/pub/gnu, ftp.denet.dk,
  ftp.stacken.kth.se, isy.liu.se, ftp.luth.se:/pub/unix/gnu,
  ftp.sunet.se:/pub/gnu, archive.eu.net
        SOUTH AMERICA: ftp.inf.utfsm.cl:/pub/gnu, ftp.unicamp.br:/pub/gnu
        WESTERN CANADA: ftp.cs.ubc.ca:/mirror2/gnu
        USA: wuarchive.wustl.edu:/systems/gnu, labrea.stanford.edu,
  ftp.digex.net:/pub/gnu, ftp.kpc.com:/pub/mirror/gnu,
  f.ms.uky.edu:/pub3/gnu,
  jaguar.utah.edu:/gnustuff, ftp.hawaii.edu:/mirrors/gnu,
  uiarchive.cso.uiuc.edu:/pub/gnu, ftp.cs.columbia.edu:/archives/gnu/prep,
  col.hp.com:/mirrors/gnu, gatekeeper.dec.com:/pub/GNU,
  ftp.uu.net:/systems/gnu

]