diff options
| author | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
|---|---|---|
| committer | upstream source tree <ports@midipix.org> | 2015-03-15 20:14:05 -0400 |
| commit | 554fd8c5195424bdbcabf5de30fdc183aba391bd (patch) | |
| tree | 976dc5ab7fddf506dadce60ae936f43f58787092 /libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html | |
| download | cbb-gcc-4.6.4-upstream.tar.bz2 cbb-gcc-4.6.4-upstream.tar.xz | |
obtained gcc-4.6.4.tar.bz2 from upstream website;upstream
verified gcc-4.6.4.tar.bz2.sig;
imported gcc-4.6.4 source tree from verified upstream tarball.
downloading a git-generated archive based on the 'upstream' tag
should provide you with a source tree that is binary identical
to the one extracted from the above tarball.
if you have obtained the source via the command 'git clone',
however, do note that line-endings of files in your working
directory might differ from line-endings of the respective
files in the upstream repository.
Diffstat (limited to 'libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html')
| -rw-r--r-- | libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html | 412 |
1 files changed, 412 insertions, 0 deletions
diff --git a/libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html b/libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html new file mode 100644 index 000000000..3e35af0fa --- /dev/null +++ b/libstdc++-v3/doc/html/manual/bk01pt03ch17s04.html @@ -0,0 +1,412 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml"><head><title>Design</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"/><meta name="keywords" content=" C++ , library , debug "/><meta name="keywords" content=" ISO C++ , library "/><link rel="home" href="../spine.html" title="The GNU C++ Library"/><link rel="up" href="debug_mode.html" title="Chapter 17. Debug Mode"/><link rel="prev" href="bk01pt03ch17s03.html" title="Using"/><link rel="next" href="parallel_mode.html" title="Chapter 18. Parallel Mode"/></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Design</th></tr><tr><td align="left"><a accesskey="p" href="bk01pt03ch17s03.html">Prev</a> </td><th width="60%" align="center">Chapter 17. Debug Mode</th><td align="right"> <a accesskey="n" href="parallel_mode.html">Next</a></td></tr></table><hr/></div><div class="section" title="Design"><div class="titlepage"><div><div><h2 class="title"><a id="manual.ext.debug_mode.design"/>Design</h2></div></div></div><p> + </p><div class="section" title="Goals"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.goals"/>Goals</h3></div></div></div><p> + </p><p> The libstdc++ debug mode replaces unsafe (but efficient) standard + containers and iterators with semantically equivalent safe standard + containers and iterators to aid in debugging user programs. The + following goals directed the design of the libstdc++ debug mode:</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><span class="emphasis"><em>Correctness</em></span>: the libstdc++ debug mode must not change + the semantics of the standard library for all cases specified in + the ANSI/ISO C++ standard. The essence of this constraint is that + any valid C++ program should behave in the same manner regardless + of whether it is compiled with debug mode or release mode. In + particular, entities that are defined in namespace std in release + mode should remain defined in namespace std in debug mode, so that + legal specializations of namespace std entities will remain + valid. A program that is not valid C++ (e.g., invokes undefined + behavior) is not required to behave similarly, although the debug + mode will abort with a diagnostic when it detects undefined + behavior.</p></li><li class="listitem"><p><span class="emphasis"><em>Performance</em></span>: the additional of the libstdc++ debug mode + must not affect the performance of the library when it is compiled + in release mode. Performance of the libstdc++ debug mode is + secondary (and, in fact, will be worse than the release + mode).</p></li><li class="listitem"><p><span class="emphasis"><em>Usability</em></span>: the libstdc++ debug mode should be easy to + use. It should be easily incorporated into the user's development + environment (e.g., by requiring only a single new compiler switch) + and should produce reasonable diagnostics when it detects a + problem with the user program. Usability also involves detection + of errors when using the debug mode incorrectly, e.g., by linking + a release-compiled object against a debug-compiled object if in + fact the resulting program will not run correctly.</p></li><li class="listitem"><p><span class="emphasis"><em>Minimize recompilation</em></span>: While it is expected that + users recompile at least part of their program to use debug + mode, the amount of recompilation affects the + detect-compile-debug turnaround time. This indirectly affects the + usefulness of the debug mode, because debugging some applications + may require rebuilding a large amount of code, which may not be + feasible when the suspect code may be very localized. There are + several levels of conformance to this requirement, each with its + own usability and implementation characteristics. In general, the + higher-numbered conformance levels are more usable (i.e., require + less recompilation) but are more complicated to implement than + the lower-numbered conformance levels. + </p><div class="orderedlist"><ol class="orderedlist"><li class="listitem"><p><span class="emphasis"><em>Full recompilation</em></span>: The user must recompile his or + her entire application and all C++ libraries it depends on, + including the C++ standard library that ships with the + compiler. This must be done even if only a small part of the + program can use debugging features.</p></li><li class="listitem"><p><span class="emphasis"><em>Full user recompilation</em></span>: The user must recompile + his or her entire application and all C++ libraries it depends + on, but not the C++ standard library itself. This must be done + even if only a small part of the program can use debugging + features. This can be achieved given a full recompilation + system by compiling two versions of the standard library when + the compiler is installed and linking against the appropriate + one, e.g., a multilibs approach.</p></li><li class="listitem"><p><span class="emphasis"><em>Partial recompilation</em></span>: The user must recompile the + parts of his or her application and the C++ libraries it + depends on that will use the debugging facilities + directly. This means that any code that uses the debuggable + standard containers would need to be recompiled, but code + that does not use them (but may, for instance, use IOStreams) + would not have to be recompiled.</p></li><li class="listitem"><p><span class="emphasis"><em>Per-use recompilation</em></span>: The user must recompile the + parts of his or her application and the C++ libraries it + depends on where debugging should occur, and any other code + that interacts with those containers. This means that a set of + translation units that accesses a particular standard + container instance may either be compiled in release mode (no + checking) or debug mode (full checking), but must all be + compiled in the same way; a translation unit that does not see + that standard container instance need not be recompiled. This + also means that a translation unit <span class="emphasis"><em>A</em></span> that contains a + particular instantiation + (say, <code class="code">std::vector<int></code>) compiled in release + mode can be linked against a translation unit <span class="emphasis"><em>B</em></span> that + contains the same instantiation compiled in debug mode (a + feature not present with partial recompilation). While this + behavior is technically a violation of the One Definition + Rule, this ability tends to be very important in + practice. The libstdc++ debug mode supports this level of + recompilation. </p></li><li class="listitem"><p><span class="emphasis"><em>Per-unit recompilation</em></span>: The user must only + recompile the translation units where checking should occur, + regardless of where debuggable standard containers are + used. This has also been dubbed "<code class="code">-g</code> mode", + because the <code class="code">-g</code> compiler switch works in this way, + emitting debugging information at a per--translation-unit + granularity. We believe that this level of recompilation is in + fact not possible if we intend to supply safe iterators, leave + the program semantics unchanged, and not regress in + performance under release mode because we cannot associate + extra information with an iterator (to form a safe iterator) + without either reserving that space in release mode + (performance regression) or allocating extra memory associated + with each iterator with <code class="code">new</code> (changes the program + semantics).</p></li></ol></div><p> + </p></li></ul></div></div><div class="section" title="Methods"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.methods"/>Methods</h3></div></div></div><p> + </p><p>This section provides an overall view of the design of the + libstdc++ debug mode and details the relationship between design + decisions and the stated design goals.</p><div class="section" title="The Wrapper Model"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.wrappers"/>The Wrapper Model</h4></div></div></div><p>The libstdc++ debug mode uses a wrapper model where the + debugging versions of library components (e.g., iterators and + containers) form a layer on top of the release versions of the + library components. The debugging components first verify that the + operation is correct (aborting with a diagnostic if an error is + found) and will then forward to the underlying release-mode + container that will perform the actual work. This design decision + ensures that we cannot regress release-mode performance (because the + release-mode containers are left untouched) and partially + enables <a class="link" href="bk01pt03ch17s04.html#methods.coexistence.link" title="Link- and run-time coexistence of release- and debug-mode components">mixing debug and + release code</a> at link time, although that will not be + discussed at this time.</p><p>Two types of wrappers are used in the implementation of the debug + mode: container wrappers and iterator wrappers. The two types of + wrappers interact to maintain relationships between iterators and + their associated containers, which are necessary to detect certain + types of standard library usage errors such as dereferencing + past-the-end iterators or inserting into a container using an + iterator from a different container.</p><div class="section" title="Safe Iterators"><div class="titlepage"><div><div><h5 class="title"><a id="debug_mode.design.methods.safe_iter"/>Safe Iterators</h5></div></div></div><p>Iterator wrappers provide a debugging layer over any iterator that + is attached to a particular container, and will manage the + information detailing the iterator's state (singular, + dereferenceable, etc.) and tracking the container to which the + iterator is attached. Because iterators have a well-defined, common + interface the iterator wrapper is implemented with the iterator + adaptor class template <code class="code">__gnu_debug::_Safe_iterator</code>, + which takes two template parameters:</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><code class="code">Iterator</code>: The underlying iterator type, which must + be either the <code class="code">iterator</code> or <code class="code">const_iterator</code> + typedef from the sequence type this iterator can reference.</p></li><li class="listitem"><p><code class="code">Sequence</code>: The type of sequence that this iterator + references. This sequence must be a safe sequence (discussed below) + whose <code class="code">iterator</code> or <code class="code">const_iterator</code> typedef + is the type of the safe iterator.</p></li></ul></div></div><div class="section" title="Safe Sequences (Containers)"><div class="titlepage"><div><div><h5 class="title"><a id="debug_mode.design.methods.safe_seq"/>Safe Sequences (Containers)</h5></div></div></div><p>Container wrappers provide a debugging layer over a particular + container type. Because containers vary greatly in the member + functions they support and the semantics of those member functions + (especially in the area of iterator invalidation), container + wrappers are tailored to the container they reference, e.g., the + debugging version of <code class="code">std::list</code> duplicates the entire + interface of <code class="code">std::list</code>, adding additional semantic + checks and then forwarding operations to the + real <code class="code">std::list</code> (a public base class of the debugging + version) as appropriate. However, all safe containers inherit from + the class template <code class="code">__gnu_debug::_Safe_sequence</code>, + instantiated with the type of the safe container itself (an instance + of the curiously recurring template pattern).</p><p>The iterators of a container wrapper will be + <a class="link" href="bk01pt03ch17s04.html#debug_mode.design.methods.safe_iter" title="Safe Iterators">safe + iterators</a> that reference sequences of this type and wrap the + iterators provided by the release-mode base class. The debugging + container will use only the safe iterators within its own interface + (therefore requiring the user to use safe iterators, although this + does not change correct user code) and will communicate with the + release-mode base class with only the underlying, unsafe, + release-mode iterators that the base class exports.</p><p> The debugging version of <code class="code">std::list</code> will have the + following basic structure:</p><pre class="programlisting"> +template<typename _Tp, typename _Allocator = allocator<_Tp> + class debug-list : + public release-list<_Tp, _Allocator>, + public __gnu_debug::_Safe_sequence<debug-list<_Tp, _Allocator> > + { + typedef release-list<_Tp, _Allocator> _Base; + typedef debug-list<_Tp, _Allocator> _Self; + + public: + typedef __gnu_debug::_Safe_iterator<typename _Base::iterator, _Self> iterator; + typedef __gnu_debug::_Safe_iterator<typename _Base::const_iterator, _Self> const_iterator; + + // duplicate std::list interface with debugging semantics + }; +</pre></div></div><div class="section" title="Precondition Checking"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.precond"/>Precondition Checking</h4></div></div></div><p>The debug mode operates primarily by checking the preconditions of + all standard library operations that it supports. Preconditions that + are always checked (regardless of whether or not we are in debug + mode) are checked via the <code class="code">__check_xxx</code> macros defined + and documented in the source + file <code class="code">include/debug/debug.h</code>. Preconditions that may or + may not be checked, depending on the debug-mode + macro <code class="code">_GLIBCXX_DEBUG</code>, are checked via + the <code class="code">__requires_xxx</code> macros defined and documented in the + same source file. Preconditions are validated using any additional + information available at run-time, e.g., the containers that are + associated with a particular iterator, the position of the iterator + within those containers, the distance between two iterators that may + form a valid range, etc. In the absence of suitable information, + e.g., an input iterator that is not a safe iterator, these + precondition checks will silently succeed.</p><p>The majority of precondition checks use the aforementioned macros, + which have the secondary benefit of having prewritten debug + messages that use information about the current status of the + objects involved (e.g., whether an iterator is singular or what + sequence it is attached to) along with some static information + (e.g., the names of the function parameters corresponding to the + objects involved). When not using these macros, the debug mode uses + either the debug-mode assertion + macro <code class="code">_GLIBCXX_DEBUG_ASSERT</code> , its pedantic + cousin <code class="code">_GLIBCXX_DEBUG_PEDASSERT</code>, or the assertion + check macro that supports more advance formulation of error + messages, <code class="code">_GLIBCXX_DEBUG_VERIFY</code>. These macros are + documented more thoroughly in the debug mode source code.</p></div><div class="section" title="Release- and debug-mode coexistence"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.coexistence"/>Release- and debug-mode coexistence</h4></div></div></div><p>The libstdc++ debug mode is the first debug mode we know of that + is able to provide the "Per-use recompilation" (4) guarantee, that + allows release-compiled and debug-compiled code to be linked and + executed together without causing unpredictable behavior. This + guarantee minimizes the recompilation that users are required to + perform, shortening the detect-compile-debug bug hunting cycle + and making the debug mode easier to incorporate into development + environments by minimizing dependencies.</p><p>Achieving link- and run-time coexistence is not a trivial + implementation task. To achieve this goal we required a small + extension to the GNU C++ compiler (since incorporated into the C++0x language specification, described in the GCC Manual for the C++ language as + <a class="link" href="http://gcc.gnu.org/onlinedocs/gcc/Namespace-Association.html#Namespace-Association">namespace + association</a>), and a complex organization of debug- and + release-modes. The end result is that we have achieved per-use + recompilation but have had to give up some checking of the + <code class="code">std::basic_string</code> class template (namely, safe + iterators). +</p><div class="section" title="Compile-time coexistence of release- and debug-mode components"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.compile"/>Compile-time coexistence of release- and debug-mode components</h5></div></div></div><p>Both the release-mode components and the debug-mode + components need to exist within a single translation unit so that + the debug versions can wrap the release versions. However, only one + of these components should be user-visible at any particular + time with the standard name, e.g., <code class="code">std::list</code>. </p><p>In release mode, we define only the release-mode version of the + component with its standard name and do not include the debugging + component at all. The release mode version is defined within the + namespace <code class="code">std</code>. Minus the namespace associations, this + method leaves the behavior of release mode completely unchanged from + its behavior prior to the introduction of the libstdc++ debug + mode. Here's an example of what this ends up looking like, in + C++.</p><pre class="programlisting"> +namespace std +{ + template<typename _Tp, typename _Alloc = allocator<_Tp> > + class list + { + // ... + }; +} // namespace std +</pre><p>In debug mode we include the release-mode container (which is now +defined in the namespace <code class="code">__cxx1998</code>) and also the +debug-mode container. The debug-mode container is defined within the +namespace <code class="code">__debug</code>, which is associated with namespace +<code class="code">std</code> via the C++0x namespace association language feature. This +method allows the debug and release versions of the same component to +coexist at compile-time and link-time without causing an unreasonable +maintenance burden, while minimizing confusion. Again, this boils down +to C++ code as follows:</p><pre class="programlisting"> +namespace std +{ + namespace __cxx1998 + { + template<typename _Tp, typename _Alloc = allocator<_Tp> > + class list + { + // ... + }; + } // namespace __gnu_norm + + namespace __debug + { + template<typename _Tp, typename _Alloc = allocator<_Tp> > + class list + : public __cxx1998::list<_Tp, _Alloc>, + public __gnu_debug::_Safe_sequence<list<_Tp, _Alloc> > + { + // ... + }; + } // namespace __cxx1998 + + // namespace __debug __attribute__ ((strong)); + inline namespace __debug { } +} +</pre></div><div class="section" title="Link- and run-time coexistence of release- and debug-mode components"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.link"/>Link- and run-time coexistence of release- and + debug-mode components</h5></div></div></div><p>Because each component has a distinct and separate release and +debug implementation, there is no issue with link-time +coexistence: the separate namespaces result in different mangled +names, and thus unique linkage.</p><p>However, components that are defined and used within the C++ +standard library itself face additional constraints. For instance, +some of the member functions of <code class="code"> std::moneypunct</code> return +<code class="code">std::basic_string</code>. Normally, this is not a problem, but +with a mixed mode standard library that could be using either +debug-mode or release-mode <code class="code"> basic_string</code> objects, things +get more complicated. As the return value of a function is not +encoded into the mangled name, there is no way to specify a +release-mode or a debug-mode string. In practice, this results in +runtime errors. A simplified example of this problem is as follows. +</p><p> Take this translation unit, compiled in debug-mode: </p><pre class="programlisting"> +// -D_GLIBCXX_DEBUG +#include <string> + +std::string test02(); + +std::string test01() +{ + return test02(); +} + +int main() +{ + test01(); + return 0; +} +</pre><p> ... and linked to this translation unit, compiled in release mode:</p><pre class="programlisting"> +#include <string> + +std::string +test02() +{ + return std::string("toast"); +} +</pre><p> For this reason we cannot easily provide safe iterators for + the <code class="code">std::basic_string</code> class template, as it is present + throughout the C++ standard library. For instance, locale facets + define typedefs that include <code class="code">basic_string</code>: in a mixed + debug/release program, should that typedef be based on the + debug-mode <code class="code">basic_string</code> or the + release-mode <code class="code">basic_string</code>? While the answer could be + "both", and the difference hidden via renaming a la the + debug/release containers, we must note two things about locale + facets:</p><div class="orderedlist"><ol class="orderedlist"><li class="listitem"><p>They exist as shared state: one can create a facet in one + translation unit and access the facet via the same type name in a + different translation unit. This means that we cannot have two + different versions of locale facets, because the types would not be + the same across debug/release-mode translation unit barriers.</p></li><li class="listitem"><p>They have virtual functions returning strings: these functions + mangle in the same way regardless of the mangling of their return + types (see above), and their precise signatures can be relied upon + by users because they may be overridden in derived classes.</p></li></ol></div><p>With the design of libstdc++ debug mode, we cannot effectively hide + the differences between debug and release-mode strings from the + user. Failure to hide the differences may result in unpredictable + behavior, and for this reason we have opted to only + perform <code class="code">basic_string</code> changes that do not require ABI + changes. The effect on users is expected to be minimal, as there are + simple alternatives (e.g., <code class="code">__gnu_debug::basic_string</code>), + and the usability benefit we gain from the ability to mix debug- and + release-compiled translation units is enormous.</p></div><div class="section" title="Alternatives for Coexistence"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.alt"/>Alternatives for Coexistence</h5></div></div></div><p>The coexistence scheme above was chosen over many alternatives, + including language-only solutions and solutions that also required + extensions to the C++ front end. The following is a partial list of + solutions, with justifications for our rejection of each.</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><span class="emphasis"><em>Completely separate debug/release libraries</em></span>: This is by + far the simplest implementation option, where we do not allow any + coexistence of debug- and release-compiled translation units in a + program. This solution has an extreme negative affect on usability, + because it is quite likely that some libraries an application + depends on cannot be recompiled easily. This would not meet + our <span class="emphasis"><em>usability</em></span> or <span class="emphasis"><em>minimize recompilation</em></span> criteria + well.</p></li><li class="listitem"><p><span class="emphasis"><em>Add a <code class="code">Debug</code> boolean template parameter</em></span>: + Partial specialization could be used to select the debug + implementation when <code class="code">Debug == true</code>, and the state + of <code class="code">_GLIBCXX_DEBUG</code> could decide whether the + default <code class="code">Debug</code> argument is <code class="code">true</code> + or <code class="code">false</code>. This option would break conformance with the + C++ standard in both debug <span class="emphasis"><em>and</em></span> release modes. This would + not meet our <span class="emphasis"><em>correctness</em></span> criteria. </p></li><li class="listitem"><p><span class="emphasis"><em>Packaging a debug flag in the allocators</em></span>: We could + reuse the <code class="code">Allocator</code> template parameter of containers + by adding a sentinel wrapper <code class="code">debug<></code> that + signals the user's intention to use debugging, and pick up + the <code class="code">debug<></code> allocator wrapper in a partial + specialization. However, this has two drawbacks: first, there is a + conformance issue because the default allocator would not be the + standard-specified <code class="code">std::allocator<T></code>. Secondly + (and more importantly), users that specify allocators instead of + implicitly using the default allocator would not get debugging + containers. Thus this solution fails the <span class="emphasis"><em>correctness</em></span> + criteria.</p></li><li class="listitem"><p><span class="emphasis"><em>Define debug containers in another namespace, and employ + a <code class="code">using</code> declaration (or directive)</em></span>: This is an + enticing option, because it would eliminate the need for + the <code class="code">link_name</code> extension by aliasing the + templates. However, there is no true template aliasing mechanism + in C++, because both <code class="code">using</code> directives and using + declarations disallow specialization. This method fails + the <span class="emphasis"><em>correctness</em></span> criteria.</p></li><li class="listitem"><p><span class="emphasis"><em> Use implementation-specific properties of anonymous + namespaces. </em></span> + See <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2003-08/msg00004.html"> this post + </a> + This method fails the <span class="emphasis"><em>correctness</em></span> criteria.</p></li><li class="listitem"><p><span class="emphasis"><em>Extension: allow reopening on namespaces</em></span>: This would + allow the debug mode to effectively alias the + namespace <code class="code">std</code> to an internal namespace, such + as <code class="code">__gnu_std_debug</code>, so that it is completely + separate from the release-mode <code class="code">std</code> namespace. While + this will solve some renaming problems and ensure that + debug- and release-compiled code cannot be mixed unsafely, it ensures that + debug- and release-compiled code cannot be mixed at all. For + instance, the program would have two <code class="code">std::cout</code> + objects! This solution would fails the <span class="emphasis"><em>minimize + recompilation</em></span> requirement, because we would only be able to + support option (1) or (2).</p></li><li class="listitem"><p><span class="emphasis"><em>Extension: use link name</em></span>: This option involves + complicated re-naming between debug-mode and release-mode + components at compile time, and then a g++ extension called <span class="emphasis"><em> + link name </em></span> to recover the original names at link time. There + are two drawbacks to this approach. One, it's very verbose, + relying on macro renaming at compile time and several levels of + include ordering. Two, ODR issues remained with container member + functions taking no arguments in mixed-mode settings resulting in + equivalent link names, <code class="code"> vector::push_back() </code> being + one example. + See <a class="link" href="http://gcc.gnu.org/ml/libstdc++/2003-08/msg00177.html">link + name</a> </p></li></ul></div><p>Other options may exist for implementing the debug mode, many of + which have probably been considered and others that may still be + lurking. This list may be expanded over time to include other + options that we could have implemented, but in all cases the full + ramifications of the approach (as measured against the design goals + for a libstdc++ debug mode) should be considered first. The DejaGNU + testsuite includes some testcases that check for known problems with + some solutions (e.g., the <code class="code">using</code> declaration solution + that breaks user specialization), and additional testcases will be + added as we are able to identify other typical problem cases. These + test cases will serve as a benchmark by which we can compare debug + mode implementations.</p></div></div></div><div class="section" title="Other Implementations"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.other"/>Other Implementations</h3></div></div></div><p> + </p><p> There are several existing implementations of debug modes for C++ + standard library implementations, although none of them directly + supports debugging for programs using libstdc++. The existing + implementations include:</p><div class="itemizedlist"><ul class="itemizedlist"><li class="listitem"><p><a class="link" href="http://www.mathcs.sjsu.edu/faculty/horstman/safestl.html">SafeSTL</a>: + SafeSTL was the original debugging version of the Standard Template + Library (STL), implemented by Cay S. Horstmann on top of the + Hewlett-Packard STL. Though it inspired much work in this area, it + has not been kept up-to-date for use with modern compilers or C++ + standard library implementations.</p></li><li class="listitem"><p><a class="link" href="http://www.stlport.org/">STLport</a>: STLport is a free + implementation of the C++ standard library derived from the <a class="link" href="http://www.sgi.com/tech/stl/">SGI implementation</a>, and + ported to many other platforms. It includes a debug mode that uses a + wrapper model (that in some ways inspired the libstdc++ debug mode + design), although at the time of this writing the debug mode is + somewhat incomplete and meets only the "Full user recompilation" (2) + recompilation guarantee by requiring the user to link against a + different library in debug mode vs. release mode.</p></li><li class="listitem"><p>Metrowerks CodeWarrior: The C++ standard library + that ships with Metrowerks CodeWarrior includes a debug mode. It is + a full debug-mode implementation (including debugging for + CodeWarrior extensions) and is easy to use, although it meets only + the "Full recompilation" (1) recompilation + guarantee.</p></li></ul></div></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td align="left"><a accesskey="p" href="bk01pt03ch17s03.html">Prev</a> </td><td align="center"><a accesskey="u" href="debug_mode.html">Up</a></td><td align="right"> <a accesskey="n" href="parallel_mode.html">Next</a></td></tr><tr><td align="left" valign="top">Using </td><td align="center"><a accesskey="h" href="../spine.html">Home</a></td><td align="right" valign="top"> Chapter 18. Parallel Mode</td></tr></table></div></body></html> |