--- /dev/null
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
+<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Debugging Support</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" C++ , debug " /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="using.html" title="Chapter 3. Using" /><link rel="prev" href="using_exceptions.html" title="Exceptions" /><link rel="next" href="support.html" title="Part II. Support" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Debugging Support</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><th width="60%" align="center">Chapter 3. Using</th><td width="20%" align="right"> <a accesskey="n" href="support.html">Next</a></td></tr></table><hr /></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.intro.using.debug"></a>Debugging Support</h2></div></div></div><p>
+ There are numerous things that can be done to improve the ease with
+ which C++ binaries are debugged when using the GNU tool chain. Here
+ are some of them.
+</p><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compiler"></a>Using <span class="command"><strong>g++</strong></span></h3></div></div></div><p>
+ Compiler flags determine how debug information is transmitted
+ between compilation and debug or analysis tools.
+ </p><p>
+ The default optimizations and debug flags for a libstdc++ build
+ are <code class="code">-g -O2</code>. However, both debug and optimization
+ flags can be varied to change debugging characteristics. For
+ instance, turning off all optimization via the <code class="code">-g -O0
+ -fno-inline</code> flags will disable inlining and optimizations,
+ and add debugging information, so that stepping through all functions,
+ (including inlined constructors and destructors) is possible. In
+ addition, <code class="code">-fno-eliminate-unused-debug-types</code> can be
+ used when additional debug information, such as nested class info,
+ is desired.
+</p><p>
+ Or, the debug format that the compiler and debugger use to
+ communicate information about source constructs can be changed via
+ <code class="code">-gdwarf-2</code> or <code class="code">-gstabs</code> flags: some debugging
+ formats permit more expressive type and scope information to be
+ shown in gdb. Expressiveness can be enhanced by flags like
+ <code class="code">-g3</code>. The default debug information for a particular
+ platform can be identified via the value set by the
+ PREFERRED_DEBUGGING_TYPE macro in the gcc sources.
+</p><p>
+ Many other options are available: please see <a class="ulink" href="http://gcc.gnu.org/onlinedocs/gcc/Debugging-Options.html#Debugging%20Options" target="_top">"Options
+ for Debugging Your Program"</a> in Using the GNU Compiler
+ Collection (GCC) for a complete list.
+</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.req"></a>Debug Versions of Library Binary Files</h3></div></div></div><p>
+ If you would like debug symbols in libstdc++, there are two ways to
+ build libstdc++ with debug flags. The first is to run make from the
+ toplevel in a freshly-configured tree with
+</p><pre class="programlisting">
+ --enable-libstdcxx-debug
+</pre><p>and perhaps</p><pre class="programlisting">
+ --enable-libstdcxx-debug-flags='...'
+</pre><p>
+ to create a separate debug build. Both the normal build and the
+ debug build will persist, without having to specify
+ <code class="code">CXXFLAGS</code>, and the debug library will be installed in a
+ separate directory tree, in <code class="code">(prefix)/lib/debug</code>. For
+ more information, look at the <a class="link" href="configure.html" title="Configure">configuration</a> section.
+</p><p>
+ A second approach is to use the configuration flags
+</p><pre class="programlisting">
+ make CXXFLAGS='-g3 -fno-inline -O0' all
+</pre><p>
+ This quick and dirty approach is often sufficient for quick
+ debugging tasks, when you cannot or don't want to recompile your
+ application to use the <a class="link" href="debug_mode.html" title="Chapter 30. Debug Mode">debug mode</a>.</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.memory"></a>Memory Leak Hunting</h3></div></div></div><p>
+ There are various third party memory tracing and debug utilities
+ that can be used to provide detailed memory allocation information
+ about C++ code. An exhaustive list of tools is not going to be
+ attempted, but includes <code class="code">mtrace</code>, <code class="code">valgrind</code>,
+ <code class="code">mudflap</code>, and the non-free commercial product
+ <code class="code">purify</code>. In addition, <code class="code">libcwd</code> has a
+ replacement for the global new and delete operators that can track
+ memory allocation and deallocation and provide useful memory
+ statistics.
+</p><p>
+ Regardless of the memory debugging tool being used, there is one
+ thing of great importance to keep in mind when debugging C++ code
+ that uses <code class="code">new</code> and <code class="code">delete</code>: there are
+ different kinds of allocation schemes that can be used by <code class="code">
+ std::allocator </code>. For implementation details, see the <a class="link" href="ext_allocators.html#manual.ext.allocator.mt" title="mt_allocator">mt allocator</a> documentation and
+ look specifically for <code class="code">GLIBCXX_FORCE_NEW</code>.
+</p><p>
+ In a nutshell, the default allocator used by <code class="code">
+ std::allocator</code> is a high-performance pool allocator, and can
+ give the mistaken impression that in a suspect executable, memory is
+ being leaked, when in reality the memory "leak" is a pool being used
+ by the library's allocator and is reclaimed after program
+ termination.
+</p><p>
+ For valgrind, there are some specific items to keep in mind. First
+ of all, use a version of valgrind that will work with current GNU
+ C++ tools: the first that can do this is valgrind 1.0.4, but later
+ versions should work at least as well. Second of all, use a
+ completely unoptimized build to avoid confusing valgrind. Third, use
+ GLIBCXX_FORCE_NEW to keep extraneous pool allocation noise from
+ cluttering debug information.
+</p><p>
+ Fourth, it may be necessary to force deallocation in other libraries
+ as well, namely the "C" library. On linux, this can be accomplished
+ with the appropriate use of the <code class="code">__cxa_atexit</code> or
+ <code class="code">atexit</code> functions.
+</p><pre class="programlisting">
+ #include <cstdlib>
+
+ extern "C" void __libc_freeres(void);
+
+ void do_something() { }
+
+ int main()
+ {
+ atexit(__libc_freeres);
+ do_something();
+ return 0;
+ }
+</pre><p>or, using <code class="code">__cxa_atexit</code>:</p><pre class="programlisting">
+ extern "C" void __libc_freeres(void);
+ extern "C" int __cxa_atexit(void (*func) (void *), void *arg, void *d);
+
+ void do_something() { }
+
+ int main()
+ {
+ extern void* __dso_handle __attribute__ ((__weak__));
+ __cxa_atexit((void (*) (void *)) __libc_freeres, NULL,
+ &__dso_handle ? __dso_handle : NULL);
+ do_test();
+ return 0;
+ }
+</pre><p>
+ Suggested valgrind flags, given the suggestions above about setting
+ up the runtime environment, library, and test file, might be:
+</p><pre class="programlisting">
+ valgrind -v --num-callers=20 --leak-check=yes --leak-resolution=high --show-reachable=yes a.out
+</pre></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.gdb"></a>Using <span class="command"><strong>gdb</strong></span></h3></div></div></div><p>
+ </p><p>
+ Many options are available for gdb itself: please see <a class="ulink" href="http://sources.redhat.com/gdb/current/onlinedocs/gdb_13.html#SEC125" target="_top">
+ "GDB features for C++" </a> in the gdb documentation. Also
+ recommended: the other parts of this manual.
+</p><p>
+ These settings can either be switched on in at the gdb command line,
+ or put into a .gdbint file to establish default debugging
+ characteristics, like so:
+</p><pre class="programlisting">
+ set print pretty on
+ set print object on
+ set print static-members on
+ set print vtbl on
+ set print demangle on
+ set demangle-style gnu-v3
+</pre></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.exceptions"></a>Tracking uncaught exceptions</h3></div></div></div><p>
+ The <a class="link" href="verbose_termination.html" title="Verbose Terminate Handler">verbose
+ termination handler</a> gives information about uncaught
+ exceptions which are killing the program. It is described in the
+ linked-to page.
+</p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.debug_mode"></a>Debug Mode</h3></div></div></div><p> The <a class="link" href="debug_mode.html" title="Chapter 30. Debug Mode">Debug Mode</a>
+ has compile and run-time checks for many containers.
+ </p></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="debug.compile_time_checks"></a>Compile Time Checking</h3></div></div></div><p> The <a class="link" href="ext_compile_checks.html" title="Chapter 29. Compile Time Checks">Compile-Time
+ Checks</a> Extension has compile-time checks for many algorithms.
+ </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="using_exceptions.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="using.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="support.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Exceptions </td><td width="20%" align="center"><a accesskey="h" href="../spine.html">Home</a></td><td width="40%" align="right" valign="top"> Part II.
+ Support
+
+</td></tr></table></div></body></html>
projects / msp430-gcc.git / blobdiff