Mercurial > hg > index.cgi

annotate docs/lwasm.txt @ 577:e49d24f4a9a5

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Correct bug in the object file output code leading to stack corruption It turns out leaving a pointer to a stack allocated temporary in a persistent data structure is not conducive to correct program operation. Undo the export check setup in the object file output sequence so a pointer to stack allocated memory is not left hanging when the function returns. This seems to correct at least one mysterious crash bug, and possibly others. Thanks to Boisy Pitre for reporting the crash bug that led to this discovery, as well as a previous crash bug that likely has the same root cause. Additional thanks to Ciaran Anscomb whose debugger wielding wizardry revealed the exact location of this particular bit of unbrilliance.
author William Astle <lost@l-w.ca>
date Sat, 03 Aug 2024 14:30:06 -0600
parents 2c24602be78f
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
0
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
1 LWASM 2.0
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
2 =========
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
3
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
4 LWASM is a cross-assembler for the MC6809 and HD6309 CPUs. It should
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
5 assemble most reasonable EDTASM compatible source code. This document is not
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
6 intended to teach assembly language for these CPUs but rather to document
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
7 the behaviour of LWASM.
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
8
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
9
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
10 TARGETS
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
11 -------
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
12
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
13 LWASM supports several targets for assembly. These are decb, raw, and obj.
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
14
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
15 The raw target generates a raw binary output. This is useful for building
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
16 ROMs and other items that are not intended to be loaded by any kind of
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
17 loader. In this mode, the ORG directive is merely advisory and does not
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
18 affect the output except for the addresses symbols are defined to have.
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
19
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
20 The decb target generates output that can be loaded with the CLOADM or LOADM
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
21 commands in Color Basic. There will be approximately one segment in the
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
22 output file for every ORG statement after which any code is emitted. (That
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
23 is, two ORG statements in a row will not generate two output segments.)
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
24 This is approximately equivalent to running A/AO in EDTASM.
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
25
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
26 The obj target generates output that is intended to be linked later with
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
27 LWLINK. This target disallows the use of ORG for defining anything other
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
28 than constants. In this target, source files consist of a number of sections
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
29 (SECTION/ENDSECTION). Nothing outside of a section is permitted to cause any
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
30 output at all. Use of an ORG statement within a section is an error. This
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
31 target also permits tagging symbols for export (EXPORT) and marking a symbol
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
32 as externally defined (IMPORT/EXTERN). The linker will resolve any external
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
33 references at link time. Additionally, any inter-section references will be
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
34 resolved by the linker. All code in each section is assembled with an
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
35 implicit origin of 0. SETDP has no effect because the assembler has no idea
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
36 what address the linker will assign to the code when it is linked. Any
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
37 direct addressing modes will default to extended to allow for the linker to
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
38 perform relocations. Intersegment references and external references will
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
39 use 16 bit relative addressing but intrasegment internal references may use
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
40 8 bit relative addressing. Forced 8 bit direct modes are probably an error
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
41 but are permitted on the theory that the programmer might know something the
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
42 assembler doesn't.
2c24602be78f Initial import from lwtools 3.0.1 version, with new hand built build system and file reorganization
lost@l-w.ca
parents:
diff changeset
43