129 lines
6.3 KiB
HTML
129 lines
6.3 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Arrays - STABS</title>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html">
|
||
|
|
<meta name="description" content="STABS">
|
||
|
|
<meta name="generator" content="makeinfo 4.13">
|
||
|
|
<link title="Top" rel="start" href="index.html#Top">
|
||
|
|
<link rel="up" href="Types.html#Types" title="Types">
|
||
|
|
<link rel="prev" href="Subranges.html#Subranges" title="Subranges">
|
||
|
|
<link rel="next" href="Strings.html#Strings" title="Strings">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
Copyright (C) 1992-2019 Free Software Foundation, Inc.
|
||
|
|
Contributed by Cygnus Support. Written by Julia Menapace, Jim Kingdon,
|
||
|
|
and David MacKenzie.
|
||
|
|
|
||
|
|
Permission is granted to copy, distribute and/or modify this document
|
||
|
|
under the terms of the GNU Free Documentation License, Version 1.3 or
|
||
|
|
any later version published by the Free Software Foundation; with no
|
||
|
|
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
|
||
|
|
Texts. A copy of the license is included in the section entitled ``GNU
|
||
|
|
Free Documentation License''.-->
|
||
|
|
<meta http-equiv="Content-Style-Type" content="text/css">
|
||
|
|
<style type="text/css"><!--
|
||
|
|
pre.display { font-family:inherit }
|
||
|
|
pre.format { font-family:inherit }
|
||
|
|
pre.smalldisplay { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallformat { font-family:inherit; font-size:smaller }
|
||
|
|
pre.smallexample { font-size:smaller }
|
||
|
|
pre.smalllisp { font-size:smaller }
|
||
|
|
span.sc { font-variant:small-caps }
|
||
|
|
span.roman { font-family:serif; font-weight:normal; }
|
||
|
|
span.sansserif { font-family:sans-serif; font-weight:normal; }
|
||
|
|
--></style>
|
||
|
|
</head>
|
||
|
|
<body>
|
||
|
|
<div class="node">
|
||
|
|
<a name="Arrays"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="Strings.html#Strings">Strings</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Subranges.html#Subranges">Subranges</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Types.html#Types">Types</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h3 class="section">5.5 Array Types</h3>
|
||
|
|
|
||
|
|
<p>Arrays use the ‘<samp><span class="samp">a</span></samp>’ type descriptor. Following the type descriptor
|
||
|
|
is the type of the index and the type of the array elements. If the
|
||
|
|
index type is a range type, it ends in a semicolon; otherwise
|
||
|
|
(for example, if it is a type reference), there does not
|
||
|
|
appear to be any way to tell where the types are separated. In an
|
||
|
|
effort to clean up this mess, IBM documents the two types as being
|
||
|
|
separated by a semicolon, and a range type as not ending in a semicolon
|
||
|
|
(but this is not right for range types which are not array indexes,
|
||
|
|
see <a href="Subranges.html#Subranges">Subranges</a>). I think probably the best solution is to specify
|
||
|
|
that a semicolon ends a range type, and that the index type and element
|
||
|
|
type of an array are separated by a semicolon, but that if the index
|
||
|
|
type is a range type, the extra semicolon can be omitted. GDB (at least
|
||
|
|
through version 4.9) doesn't support any kind of index type other than a
|
||
|
|
range anyway; I'm not sure about dbx.
|
||
|
|
|
||
|
|
<p>It is well established, and widely used, that the type of the index,
|
||
|
|
unlike most types found in the stabs, is merely a type definition, not
|
||
|
|
type information (see <a href="String-Field.html#String-Field">String Field</a>) (that is, it need not start with
|
||
|
|
‘<samp><var>type-number</var><span class="samp">=</span></samp>’ if it is defining a new type). According to a
|
||
|
|
comment in GDB, this is also true of the type of the array elements; it
|
||
|
|
gives ‘<samp><span class="samp">ar1;1;10;ar1;1;10;4</span></samp>’ as a legitimate way to express a two
|
||
|
|
dimensional array. According to AIX documentation, the element type
|
||
|
|
must be type information. GDB accepts either.
|
||
|
|
|
||
|
|
<p>The type of the index is often a range type, expressed as the type
|
||
|
|
descriptor ‘<samp><span class="samp">r</span></samp>’ and some parameters. It defines the size of the
|
||
|
|
array. In the example below, the range ‘<samp><span class="samp">r1;0;2;</span></samp>’ defines an index
|
||
|
|
type which is a subrange of type 1 (integer), with a lower bound of 0
|
||
|
|
and an upper bound of 2. This defines the valid range of subscripts of
|
||
|
|
a three-element C array.
|
||
|
|
|
||
|
|
<p>For example, the definition:
|
||
|
|
|
||
|
|
<pre class="example"> char char_vec[3] = {'a','b','c'};
|
||
|
|
</pre>
|
||
|
|
<p class="noindent">produces the output:
|
||
|
|
|
||
|
|
<pre class="example"> .stabs "char_vec:G19=ar1;0;2;2",32,0,0,0
|
||
|
|
.global _char_vec
|
||
|
|
.align 4
|
||
|
|
_char_vec:
|
||
|
|
.byte 97
|
||
|
|
.byte 98
|
||
|
|
.byte 99
|
||
|
|
</pre>
|
||
|
|
<p>If an array is <dfn>packed</dfn>, the elements are spaced more
|
||
|
|
closely than normal, saving memory at the expense of speed. For
|
||
|
|
example, an array of 3-byte objects might, if unpacked, have each
|
||
|
|
element aligned on a 4-byte boundary, but if packed, have no padding.
|
||
|
|
One way to specify that something is packed is with type attributes
|
||
|
|
(see <a href="String-Field.html#String-Field">String Field</a>). In the case of arrays, another is to use the
|
||
|
|
‘<samp><span class="samp">P</span></samp>’ type descriptor instead of ‘<samp><span class="samp">a</span></samp>’. Other than specifying a
|
||
|
|
packed array, ‘<samp><span class="samp">P</span></samp>’ is identical to ‘<samp><span class="samp">a</span></samp>’.
|
||
|
|
|
||
|
|
<!-- FIXME-what is it? A pointer? -->
|
||
|
|
<p>An open array is represented by the ‘<samp><span class="samp">A</span></samp>’ type descriptor followed by
|
||
|
|
type information specifying the type of the array elements.
|
||
|
|
|
||
|
|
<!-- FIXME: what is the format of this type? A pointer to a vector of pointers? -->
|
||
|
|
<p>An N-dimensional dynamic array is represented by
|
||
|
|
|
||
|
|
<pre class="example"> D <var>dimensions</var> ; <var>type-information</var>
|
||
|
|
</pre>
|
||
|
|
<!-- Does dimensions really have this meaning? The AIX documentation -->
|
||
|
|
<!-- doesn't say. -->
|
||
|
|
<p><var>dimensions</var> is the number of dimensions; <var>type-information</var>
|
||
|
|
specifies the type of the array elements.
|
||
|
|
|
||
|
|
<!-- FIXME: what is the format of this type? A pointer to some offsets in -->
|
||
|
|
<!-- another array? -->
|
||
|
|
<p>A subarray of an N-dimensional array is represented by
|
||
|
|
|
||
|
|
<pre class="example"> E <var>dimensions</var> ; <var>type-information</var>
|
||
|
|
</pre>
|
||
|
|
<!-- Does dimensions really have this meaning? The AIX documentation -->
|
||
|
|
<!-- doesn't say. -->
|
||
|
|
<p><var>dimensions</var> is the number of dimensions; <var>type-information</var>
|
||
|
|
specifies the type of the array elements.
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|