191 lines
8.4 KiB
HTML
191 lines
8.4 KiB
HTML
|
<html lang="en">
|
||
|
|
<head>
|
||
|
|
<title>Blocks In Python - 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="Python-API.html#Python-API" title="Python API">
|
||
|
|
<link rel="prev" href="Frames-In-Python.html#Frames-In-Python" title="Frames In Python">
|
||
|
|
<link rel="next" href="Symbols-In-Python.html#Symbols-In-Python" title="Symbols In Python">
|
||
|
|
<link href="http://www.gnu.org/software/texinfo/" rel="generator-home" title="Texinfo Homepage">
|
||
|
|
<!--
|
||
|
|
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.''
|
||
|
|
-->
|
||
|
|
<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="Blocks-In-Python"></a>
|
||
|
|
<p>
|
||
|
|
Next: <a rel="next" accesskey="n" href="Symbols-In-Python.html#Symbols-In-Python">Symbols In Python</a>,
|
||
|
|
Previous: <a rel="previous" accesskey="p" href="Frames-In-Python.html#Frames-In-Python">Frames In Python</a>,
|
||
|
|
Up: <a rel="up" accesskey="u" href="Python-API.html#Python-API">Python API</a>
|
||
|
|
<hr>
|
||
|
|
</div>
|
||
|
|
|
||
|
|
<h5 class="subsubsection">23.2.2.26 Accessing blocks from Python</h5>
|
||
|
|
|
||
|
|
<p><a name="index-blocks-in-python-2286"></a><a name="index-gdb_002eBlock-2287"></a>
|
||
|
|
In <span class="sc">gdb</span>, symbols are stored in blocks. A block corresponds
|
||
|
|
roughly to a scope in the source code. Blocks are organized
|
||
|
|
hierarchically, and are represented individually in Python as a
|
||
|
|
<code>gdb.Block</code>. Blocks rely on debugging information being
|
||
|
|
available.
|
||
|
|
|
||
|
|
<p>A frame has a block. Please see <a href="Frames-In-Python.html#Frames-In-Python">Frames In Python</a>, for a more
|
||
|
|
in-depth discussion of frames.
|
||
|
|
|
||
|
|
<p>The outermost block is known as the <dfn>global block</dfn>. The global
|
||
|
|
block typically holds public global variables and functions.
|
||
|
|
|
||
|
|
<p>The block nested just inside the global block is the <dfn>static
|
||
|
|
block</dfn>. The static block typically holds file-scoped variables and
|
||
|
|
functions.
|
||
|
|
|
||
|
|
<p><span class="sc">gdb</span> provides a method to get a block's superblock, but there
|
||
|
|
is currently no way to examine the sub-blocks of a block, or to
|
||
|
|
iterate over all the blocks in a symbol table (see <a href="Symbol-Tables-In-Python.html#Symbol-Tables-In-Python">Symbol Tables In Python</a>).
|
||
|
|
|
||
|
|
<p>Here is a short example that should help explain blocks:
|
||
|
|
|
||
|
|
<pre class="smallexample"> /* This is in the global block. */
|
||
|
|
int global;
|
||
|
|
|
||
|
|
/* This is in the static block. */
|
||
|
|
static int file_scope;
|
||
|
|
|
||
|
|
/* 'function' is in the global block, and 'argument' is
|
||
|
|
in a block nested inside of 'function'. */
|
||
|
|
int function (int argument)
|
||
|
|
{
|
||
|
|
/* 'local' is in a block inside 'function'. It may or may
|
||
|
|
not be in the same block as 'argument'. */
|
||
|
|
int local;
|
||
|
|
|
||
|
|
{
|
||
|
|
/* 'inner' is in a block whose superblock is the one holding
|
||
|
|
'local'. */
|
||
|
|
int inner;
|
||
|
|
|
||
|
|
/* If this call is expanded by the compiler, you may see
|
||
|
|
a nested block here whose function is 'inline_function'
|
||
|
|
and whose superblock is the one holding 'inner'. */
|
||
|
|
inline_function ();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
</pre>
|
||
|
|
<p>A <code>gdb.Block</code> is iterable. The iterator returns the symbols
|
||
|
|
(see <a href="Symbols-In-Python.html#Symbols-In-Python">Symbols In Python</a>) local to the block. Python programs
|
||
|
|
should not assume that a specific block object will always contain a
|
||
|
|
given symbol, since changes in <span class="sc">gdb</span> features and
|
||
|
|
infrastructure may cause symbols move across blocks in a symbol
|
||
|
|
table.
|
||
|
|
|
||
|
|
<p>The following block-related functions are available in the <code>gdb</code>
|
||
|
|
module:
|
||
|
|
|
||
|
|
<p><a name="index-gdb_002eblock_005ffor_005fpc-2288"></a>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Function: <b>gdb.block_for_pc</b> (<var>pc</var>)<var><a name="index-gdb_002eblock_005ffor_005fpc-2289"></a></var><br>
|
||
|
|
<blockquote><p>Return the innermost <code>gdb.Block</code> containing the given <var>pc</var>
|
||
|
|
value. If the block cannot be found for the <var>pc</var> value specified,
|
||
|
|
the function will return <code>None</code>. This is identical to
|
||
|
|
<code>gdb.current_progspace().block_for_pc(pc)</code> and is included for
|
||
|
|
historical compatibility.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<p>A <code>gdb.Block</code> object has the following methods:
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Function: <b>Block.is_valid</b> ()<var><a name="index-Block_002eis_005fvalid-2290"></a></var><br>
|
||
|
|
<blockquote><p>Returns <code>True</code> if the <code>gdb.Block</code> object is valid,
|
||
|
|
<code>False</code> if not. A block object can become invalid if the block it
|
||
|
|
refers to doesn't exist anymore in the inferior. All other
|
||
|
|
<code>gdb.Block</code> methods will throw an exception if it is invalid at
|
||
|
|
the time the method is called. The block's validity is also checked
|
||
|
|
during iteration over symbols of the block.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<p>A <code>gdb.Block</code> object has the following attributes:
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.start</b><var><a name="index-Block_002estart-2291"></a></var><br>
|
||
|
|
<blockquote><p>The start address of the block. This attribute is not writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.end</b><var><a name="index-Block_002eend-2292"></a></var><br>
|
||
|
|
<blockquote><p>One past the last address that appears in the block. This attribute
|
||
|
|
is not writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.function</b><var><a name="index-Block_002efunction-2293"></a></var><br>
|
||
|
|
<blockquote><p>The name of the block represented as a <code>gdb.Symbol</code>. If the
|
||
|
|
block is not named, then this attribute holds <code>None</code>. This
|
||
|
|
attribute is not writable.
|
||
|
|
|
||
|
|
<p>For ordinary function blocks, the superblock is the static block.
|
||
|
|
However, you should note that it is possible for a function block to
|
||
|
|
have a superblock that is not the static block – for instance this
|
||
|
|
happens for an inlined function.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.superblock</b><var><a name="index-Block_002esuperblock-2294"></a></var><br>
|
||
|
|
<blockquote><p>The block containing this block. If this parent block does not exist,
|
||
|
|
this attribute holds <code>None</code>. This attribute is not writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.global_block</b><var><a name="index-Block_002eglobal_005fblock-2295"></a></var><br>
|
||
|
|
<blockquote><p>The global block associated with this block. This attribute is not
|
||
|
|
writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.static_block</b><var><a name="index-Block_002estatic_005fblock-2296"></a></var><br>
|
||
|
|
<blockquote><p>The static block associated with this block. This attribute is not
|
||
|
|
writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.is_global</b><var><a name="index-Block_002eis_005fglobal-2297"></a></var><br>
|
||
|
|
<blockquote><p><code>True</code> if the <code>gdb.Block</code> object is a global block,
|
||
|
|
<code>False</code> if not. This attribute is not
|
||
|
|
writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
<div class="defun">
|
||
|
|
— Variable: <b>Block.is_static</b><var><a name="index-Block_002eis_005fstatic-2298"></a></var><br>
|
||
|
|
<blockquote><p><code>True</code> if the <code>gdb.Block</code> object is a static block,
|
||
|
|
<code>False</code> if not. This attribute is not writable.
|
||
|
|
</p></blockquote></div>
|
||
|
|
|
||
|
|
</body></html>
|
||
|
|
|