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| author | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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| committer | alk3pInjection <webmaster@raspii.tech> | 2024-02-04 16:16:35 +0800 |
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diff --git a/share/doc/gdb/Ada-Glitches.html b/share/doc/gdb/Ada-Glitches.html new file mode 100644 index 0000000..406f94c --- /dev/null +++ b/share/doc/gdb/Ada-Glitches.html @@ -0,0 +1,178 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1988-2023 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 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>Debugging with GDB: Ada Glitches</title> + +<meta name="description" content="Debugging with GDB: Ada Glitches"> +<meta name="keywords" content="Debugging with GDB: Ada Glitches"> +<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-Source-Character-Set.html#Ada-Source-Character-Set" rel="previous" title="Ada Source Character Set"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +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.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Ada-Glitches"></a> +<div class="header"> +<p> +Previous: <a href="Ada-Source-Character-Set.html#Ada-Source-Character-Set" accesskey="p" rel="previous">Ada Source Character Set</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-Source-Character-Set.html#Ada-Source-Character-Set" accesskey="p" rel="previous">Ada Source Character Set</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> |