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112 lines
4.9 KiB
Text
112 lines
4.9 KiB
Text
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This directory contains files used for the 'mframe' software in gstep-base.
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These files are part of the GNUstep Base Library.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public
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License as published by the Free Software Foundation; either
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version 2 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free
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Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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The code in this directory was written by
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Richard Frith-Macdonald <richard@brainstorm.co.uk>.
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Inspiration for this software came from the original mframe.m by
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Andrew McCallum, and the libFoundation software by Ovidiu Predescu and
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Mircea Oancea, while the algorithms used are copied from gcc and are
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copyright the Free Software Foundation. Many code fragments are derived
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from gcc by way of libFoundation.
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These files are used by the configuration script to build a
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machine/operating-system specific 'mframe.m' file containing macros used
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to access stack frames.
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The 'mframe.m' file is simply built by wrapping a system dependant file
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between mframe.head and mframe.foot
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Advice on porting -
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See unknown/generic for an example of the following macros
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MFRAME_STACK_STRUCT
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This should be defined to 1 if functions return structures by value
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using the method where the caller places a pointer on the stack.
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Define this to 0 otherwise (eg. when the pointer to the structure is
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passed in a register).
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MFRAME_SMALL_STRUCT
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This is the size of the largest structure returned by value on
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the stack. Normally gcc returns structures of up to 8 bytes on
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the stack. If your system never returns structures on the stack,
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set this to zero rather than 8.
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NB. If __builtin_apply_args() always returns an argframe for
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structure return via pointe, you should also define this to zero.
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MFRAME_STRUCT_BYREF
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This should be defined to 1 if structure aprguments are passed
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by reference, 0 otherwise.
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MFRAME_ARGS_SIZE
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This must be set to the value computed by the apply_args_size()
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function in expr.c in the gcc source. It is the size of the
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area of memory allocated in which to pass arguments to a function.
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If you can't figure out how to determine this - try using a
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value like 128 - which will probably be far larger than required
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(and therefore somewhat inefficient) but will msot likely work.
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MFRAME_RESULT_SIZE
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This must be set to the value computed by the apply_result_size()
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function in expr.c in the gcc source. It is the size of the area
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of memory allocated in which to return a value from a function.
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If you can't figure out how to determine this - try using a
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value like 128 - which will probably be far larger than required
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(and therefore somewhat inefficient) but will msot likely work.
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MFRAME_STRUCT_ADDR(ARGFRAME,TYPES)
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If a function returns a structure by copying it into a location
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whose address is set by the caller, this macro must return that
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address within the argframe.
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Otherwise the macro must return zero.
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MFRAME_ARGS
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This macro should define a data type to be used for recording
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information about the arguments list of a method.
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See 'CUMULATIVE_ARGS' in the configuration file for your system
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in gcc for a parallel example.
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MFRAME_INIT_ARGS(CUM, RTYPE)
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This macro is used to initialise a variable (CUM) of the type
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defined by MFRAME_ARGS. The RTYPE value is the type encoding for the
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method return type, it is needed so that CUM can take int account any
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invisible first argument used for returning structures by value.
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See 'INIT_CUMULATIVE_ARGS' in the configuration file for your system
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in gcc for a parallel example.
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MFRAME_ARG_ENCODING(CUM,TYPES,STACK,DEST)
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This macro is used to to determine the encoding of arguments.
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Before initial entry,
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CUM should have been initialised using the MFRAME_INIT_ARGS() macro,
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TYPES should be a (const char*) variable initialised to a
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type-encoding string listing the arguments of a function/method,
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STACK should be an integer variable of value 0 in which the size of
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the stack arguments will be accumulated,
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DEST should be a (char*) variable initialised to a pointer to a
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buffer into which the full type encoding will be written.
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After each use of the macro, TYPES is advanced to point to the next
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argument, and DEST is advanced to point after the encoding of the
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previous argument.
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Of course, you must ensure that the buffer pointed to by DEST is
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large enough so that it does not overflow!
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You will be safe if your buffer is at least ten times as big as
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the type-encoding string you start from.
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