| <html lang="en"> |
| <head> |
| <title>Additions to Ada - Debugging with GDB</title> |
| <meta http-equiv="Content-Type" content="text/html"> |
| <meta name="description" content="Debugging with GDB"> |
| <meta name="generator" content="makeinfo 4.13"> |
| <link title="Top" rel="start" href="index.html#Top"> |
| <link rel="up" href="Ada.html#Ada" title="Ada"> |
| <link rel="prev" href="Omissions-from-Ada.html#Omissions-from-Ada" title="Omissions from Ada"> |
| <link rel="next" href="Stopping-Before-Main-Program.html#Stopping-Before-Main-Program" title="Stopping Before Main Program"> |
| <link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage"> |
| <!-- |
| Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, |
| 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
| 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.''--> |
| <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> |
| <link rel="stylesheet" type="text/css" href="../cs.css"> |
| </head> |
| <body> |
| <div class="node"> |
| <a name="Additions-to-Ada"></a> |
| <p> |
| Next: <a rel="next" accesskey="n" href="Stopping-Before-Main-Program.html#Stopping-Before-Main-Program">Stopping Before Main Program</a>, |
| Previous: <a rel="previous" accesskey="p" href="Omissions-from-Ada.html#Omissions-from-Ada">Omissions from Ada</a>, |
| Up: <a rel="up" accesskey="u" href="Ada.html#Ada">Ada</a> |
| <hr> |
| </div> |
| |
| <h5 class="subsubsection">15.4.7.3 Additions to Ada</h5> |
| |
| <p><a name="index-Ada_002c-deviations-from-865"></a> |
| As it does for other languages, <span class="sc">gdb</span> makes certain generic |
| extensions to Ada (see <a href="Expressions.html#Expressions">Expressions</a>): |
| |
| <ul> |
| <li>If the expression <var>E</var> is a variable residing in memory (typically |
| a local variable or array element) and <var>N</var> is a positive integer, |
| then <var>E</var><code>@</code><var>N</var> displays the values of <var>E</var> and the |
| <var>N</var>-1 adjacent variables following it in memory as an array. In |
| Ada, this operator is generally not necessary, since its prime use is |
| in displaying parts of an array, and slicing will usually do this in |
| Ada. However, there are occasional uses when debugging programs in |
| which certain debugging information has been optimized away. |
| |
| <li><var>B</var><code>::</code><var>var</var> means “the variable named <var>var</var> that |
| appears in function or file <var>B</var>.” When <var>B</var> is a file name, |
| you must typically surround it in single quotes. |
| |
| <li>The expression <code>{</code><var>type</var><code>} </code><var>addr</var> means “the variable of type |
| <var>type</var> that appears at address <var>addr</var>.” |
| |
| <li>A name starting with ‘<samp><span class="samp">$</span></samp>’ is a convenience variable |
| (see <a href="Convenience-Vars.html#Convenience-Vars">Convenience Vars</a>) or a machine register (see <a href="Registers.html#Registers">Registers</a>). |
| </ul> |
| |
| <p>In addition, <span class="sc">gdb</span> provides a few other shortcuts and outright |
| additions specific to Ada: |
| |
| <ul> |
| <li>The assignment statement is allowed as an expression, returning |
| its right-hand operand as its value. Thus, you may enter |
| |
| <pre class="smallexample"> (gdb) set x := y + 3 |
| (gdb) print A(tmp := y + 1) |
| </pre> |
| <li>The semicolon is allowed as an “operator,” returning as its value |
| the value of its right-hand operand. |
| This allows, for example, |
| complex conditional breaks: |
| |
| <pre class="smallexample"> (gdb) break f |
| (gdb) condition 1 (report(i); k += 1; A(k) > 100) |
| </pre> |
| <li>Rather than use catenation and symbolic character names to introduce special |
| characters into strings, one may instead use a special bracket notation, |
| which is also used to print strings. A sequence of characters of the form |
| ‘<samp><span class="samp">["</span><var>XX</var><span class="samp">"]</span></samp>’ within a string or character literal denotes the |
| (single) character whose numeric encoding is <var>XX</var> in hexadecimal. The |
| sequence of characters ‘<samp><span class="samp">["""]</span></samp>’ also denotes a single quotation mark |
| in strings. For example, |
| <pre class="smallexample"> "One line.["0a"]Next line.["0a"]" |
| </pre> |
| <p class="noindent">contains an ASCII newline character (<code>Ada.Characters.Latin_1.LF</code>) |
| after each period. |
| |
| <li>The subtype used as a prefix for the attributes <tt>'Pos</tt>, <tt>'Min</tt>, and |
| <tt>'Max</tt> is optional (and is ignored in any case). For example, it is valid |
| to write |
| |
| <pre class="smallexample"> (gdb) print 'max(x, y) |
| </pre> |
| <li>When printing arrays, <span class="sc">gdb</span> uses positional notation when the |
| array has a lower bound of 1, and uses a modified named notation otherwise. |
| For example, a one-dimensional array of three integers with a lower bound |
| of 3 might print as |
| |
| <pre class="smallexample"> (3 => 10, 17, 1) |
| </pre> |
| <p class="noindent">That is, in contrast to valid Ada, only the first component has a <code>=></code> |
| clause. |
| |
| <li>You may abbreviate attributes in expressions with any unique, |
| multi-character subsequence of |
| their names (an exact match gets preference). |
| For example, you may use <tt>a'len</tt>, <tt>a'gth</tt>, or <tt>a'lh</tt> |
| in place of <tt>a'length</tt>. |
| |
| <li><a name="index-quoting-Ada-internal-identifiers-866"></a>Since Ada is case-insensitive, the debugger normally maps identifiers you type |
| to lower case. The GNAT compiler uses upper-case characters for |
| some of its internal identifiers, which are normally of no interest to users. |
| For the rare occasions when you actually have to look at them, |
| enclose them in angle brackets to avoid the lower-case mapping. |
| For example, |
| <pre class="smallexample"> (gdb) print <JMPBUF_SAVE>[0] |
| </pre> |
| <li>Printing an object of class-wide type or dereferencing an |
| access-to-class-wide value will display all the components of the object's |
| specific type (as indicated by its run-time tag). Likewise, component |
| selection on such a value will operate on the specific type of the |
| object. |
| |
| </ul> |
| |
| </body></html> |
| |
