You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
178 lines
8.1 KiB
HTML
178 lines
8.1 KiB
HTML
4 years ago
|
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
|
||
|
|
<html>
|
||
|
|
<!-- Copyright (C) 1988-2019 Free Software Foundation, Inc.
|
||
|
|
|
||
|
|
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 the
|
||
|
|
Invariant Sections being "Free Software" and "Free Software Needs
|
||
|
|
Free Documentation", with the Front-Cover Texts being "A GNU Manual,"
|
||
|
|
and with the Back-Cover Texts as in (a) below.
|
||
|
|
|
||
|
|
(a) The FSF's Back-Cover Text is: "You are free to copy and modify
|
||
|
|
this GNU Manual. Buying copies from GNU Press supports the FSF in
|
||
|
|
developing GNU and promoting software freedom." -->
|
||
|
|
<!-- Created by GNU Texinfo 6.4, http://www.gnu.org/software/texinfo/ -->
|
||
|
|
<head>
|
||
|
|
<title>Ada Glitches (Debugging with GDB)</title>
|
||
|
|
|
||
|
|
<meta name="description" content="Ada Glitches (Debugging with GDB)">
|
||
|
|
<meta name="keywords" content="Ada Glitches (Debugging with GDB)">
|
||
|
|
<meta name="resource-type" content="document">
|
||
|
|
<meta name="distribution" content="global">
|
||
|
|
<meta name="Generator" content="makeinfo">
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
|
||
|
|
<link href="index.html#Top" rel="start" title="Top">
|
||
|
|
<link href="Concept-Index.html#Concept-Index" rel="index" title="Concept Index">
|
||
|
|
<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
|
||
|
|
<link href="Ada.html#Ada" rel="up" title="Ada">
|
||
|
|
<link href="Unsupported-Languages.html#Unsupported-Languages" rel="next" title="Unsupported Languages">
|
||
|
|
<link href="Ada-Settings.html#Ada-Settings" rel="prev" title="Ada Settings">
|
||
|
|
<style type="text/css">
|
||
|
|
<!--
|
||
|
|
a.summary-letter {text-decoration: none}
|
||
|
|
blockquote.indentedblock {margin-right: 0em}
|
||
|
|
blockquote.smallindentedblock {margin-right: 0em; font-size: smaller}
|
||
|
|
blockquote.smallquotation {font-size: smaller}
|
||
|
|
div.display {margin-left: 3.2em}
|
||
|
|
div.example {margin-left: 3.2em}
|
||
|
|
div.lisp {margin-left: 3.2em}
|
||
|
|
div.smalldisplay {margin-left: 3.2em}
|
||
|
|
div.smallexample {margin-left: 3.2em}
|
||
|
|
div.smalllisp {margin-left: 3.2em}
|
||
|
|
kbd {font-style: oblique}
|
||
|
|
pre.display {font-family: inherit}
|
||
|
|
pre.format {font-family: inherit}
|
||
|
|
pre.menu-comment {font-family: serif}
|
||
|
|
pre.menu-preformatted {font-family: serif}
|
||
|
|
pre.smalldisplay {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smallexample {font-size: smaller}
|
||
|
|
pre.smallformat {font-family: inherit; font-size: smaller}
|
||
|
|
pre.smalllisp {font-size: smaller}
|
||
|
|
span.nolinebreak {white-space: nowrap}
|
||
|
|
span.roman {font-family: initial; font-weight: normal}
|
||
|
|
span.sansserif {font-family: sans-serif; font-weight: normal}
|
||
|
|
ul.no-bullet {list-style: none}
|
||
|
|
-->
|
||
|
|
</style>
|
||
|
|
|
||
|
|
|
||
|
|
</head>
|
||
|
|
|
||
|
|
<body lang="en">
|
||
|
|
<a name="Ada-Glitches"></a>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Ada-Settings.html#Ada-Settings" accesskey="p" rel="prev">Ada Settings</a>, Up: <a href="Ada.html#Ada" accesskey="u" rel="up">Ada</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
<hr>
|
||
|
|
<a name="Known-Peculiarities-of-Ada-Mode"></a>
|
||
|
|
<h4 class="subsubsection">15.4.10.11 Known Peculiarities of Ada Mode</h4>
|
||
|
|
<a name="index-Ada_002c-problems"></a>
|
||
|
|
|
||
|
|
<p>Besides the omissions listed previously (see <a href="Omissions-from-Ada.html#Omissions-from-Ada">Omissions from Ada</a>),
|
||
|
|
we know of several problems with and limitations of Ada mode in
|
||
|
|
<small>GDB</small>,
|
||
|
|
some of which will be fixed with planned future releases of the debugger
|
||
|
|
and the GNU Ada compiler.
|
||
|
|
</p>
|
||
|
|
<ul>
|
||
|
|
<li> Static constants that the compiler chooses not to materialize as objects in
|
||
|
|
storage are invisible to the debugger.
|
||
|
|
|
||
|
|
</li><li> Named parameter associations in function argument lists are ignored (the
|
||
|
|
argument lists are treated as positional).
|
||
|
|
|
||
|
|
</li><li> Many useful library packages are currently invisible to the debugger.
|
||
|
|
|
||
|
|
</li><li> Fixed-point arithmetic, conversions, input, and output is carried out using
|
||
|
|
floating-point arithmetic, and may give results that only approximate those on
|
||
|
|
the host machine.
|
||
|
|
|
||
|
|
</li><li> The GNAT compiler never generates the prefix <code>Standard</code> for any of
|
||
|
|
the standard symbols defined by the Ada language. <small>GDB</small> knows about
|
||
|
|
this: it will strip the prefix from names when you use it, and will never
|
||
|
|
look for a name you have so qualified among local symbols, nor match against
|
||
|
|
symbols in other packages or subprograms. If you have
|
||
|
|
defined entities anywhere in your program other than parameters and
|
||
|
|
local variables whose simple names match names in <code>Standard</code>,
|
||
|
|
GNAT’s lack of qualification here can cause confusion. When this happens,
|
||
|
|
you can usually resolve the confusion
|
||
|
|
by qualifying the problematic names with package
|
||
|
|
<code>Standard</code> explicitly.
|
||
|
|
</li></ul>
|
||
|
|
|
||
|
|
<p>Older versions of the compiler sometimes generate erroneous debugging
|
||
|
|
information, resulting in the debugger incorrectly printing the value
|
||
|
|
of affected entities. In some cases, the debugger is able to work
|
||
|
|
around an issue automatically. In other cases, the debugger is able
|
||
|
|
to work around the issue, but the work-around has to be specifically
|
||
|
|
enabled.
|
||
|
|
</p>
|
||
|
|
<a name="index-set-ada-trust_002dPAD_002dover_002dXVS"></a>
|
||
|
|
<a name="index-show-ada-trust_002dPAD_002dover_002dXVS"></a>
|
||
|
|
<dl compact="compact">
|
||
|
|
<dt><code>set ada trust-PAD-over-XVS on</code></dt>
|
||
|
|
<dd><p>Configure GDB to strictly follow the GNAT encoding when computing the
|
||
|
|
value of Ada entities, particularly when <code>PAD</code> and <code>PAD___XVS</code>
|
||
|
|
types are involved (see <code>ada/exp_dbug.ads</code> in the GCC sources for
|
||
|
|
a complete description of the encoding used by the GNAT compiler).
|
||
|
|
This is the default.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
<dt><code>set ada trust-PAD-over-XVS off</code></dt>
|
||
|
|
<dd><p>This is related to the encoding using by the GNAT compiler. If <small>GDB</small>
|
||
|
|
sometimes prints the wrong value for certain entities, changing <code>ada
|
||
|
|
trust-PAD-over-XVS</code> to <code>off</code> activates a work-around which may fix
|
||
|
|
the issue. It is always safe to set <code>ada trust-PAD-over-XVS</code> to
|
||
|
|
<code>off</code>, but this incurs a slight performance penalty, so it is
|
||
|
|
recommended to leave this setting to <code>on</code> unless necessary.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<a name="index-GNAT-descriptive-types"></a>
|
||
|
|
<a name="index-GNAT-encoding"></a>
|
||
|
|
<p>Internally, the debugger also relies on the compiler following a number
|
||
|
|
of conventions known as the ‘<samp>GNAT Encoding</samp>’, all documented in
|
||
|
|
<samp>gcc/ada/exp_dbug.ads</samp> in the GCC sources. This encoding describes
|
||
|
|
how the debugging information should be generated for certain types.
|
||
|
|
In particular, this convention makes use of <em>descriptive types</em>,
|
||
|
|
which are artificial types generated purely to help the debugger.
|
||
|
|
</p>
|
||
|
|
<p>These encodings were defined at a time when the debugging information
|
||
|
|
format used was not powerful enough to describe some of the more complex
|
||
|
|
types available in Ada. Since DWARF allows us to express nearly all
|
||
|
|
Ada features, the long-term goal is to slowly replace these descriptive
|
||
|
|
types by their pure DWARF equivalent. To facilitate that transition,
|
||
|
|
a new maintenance option is available to force the debugger to ignore
|
||
|
|
those descriptive types. It allows the user to quickly evaluate how
|
||
|
|
well <small>GDB</small> works without them.
|
||
|
|
</p>
|
||
|
|
<dl compact="compact">
|
||
|
|
<dd>
|
||
|
|
<a name="index-maint-ada-set-ignore_002ddescriptive_002dtypes"></a>
|
||
|
|
</dd>
|
||
|
|
<dt><code>maintenance ada set ignore-descriptive-types [on|off]</code></dt>
|
||
|
|
<dd><p>Control whether the debugger should ignore descriptive types.
|
||
|
|
The default is not to ignore descriptives types (<code>off</code>).
|
||
|
|
</p>
|
||
|
|
<a name="index-maint-ada-show-ignore_002ddescriptive_002dtypes"></a>
|
||
|
|
</dd>
|
||
|
|
<dt><code>maintenance ada show ignore-descriptive-types</code></dt>
|
||
|
|
<dd><p>Show if descriptive types are ignored by <small>GDB</small>.
|
||
|
|
</p>
|
||
|
|
</dd>
|
||
|
|
</dl>
|
||
|
|
|
||
|
|
<hr>
|
||
|
|
<div class="header">
|
||
|
|
<p>
|
||
|
|
Previous: <a href="Ada-Settings.html#Ada-Settings" accesskey="p" rel="prev">Ada Settings</a>, Up: <a href="Ada.html#Ada" accesskey="u" rel="up">Ada</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
</body>
|
||
|
|
</html>
|