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| <!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>Design</title><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><meta name="keywords" content="C++, library, debug" /><meta name="keywords" content="ISO C++, library" /><meta name="keywords" content="ISO C++, runtime, library" /><link rel="home" href="../index.html" title="The GNU C++ Library" /><link rel="up" href="debug_mode.html" title="Chapter 17. Debug Mode" /><link rel="prev" href="debug_mode_using.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 width="20%" align="left"><a accesskey="p" href="debug_mode_using.html">Prev</a> </td><th width="60%" align="center">Chapter 17. Debug Mode</th><td width="20%" align="right"> <a accesskey="n" href="parallel_mode.html">Next</a></td></tr></table><hr /></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.ext.debug_mode.design"></a>Design</h2></div></div></div><p> |
| </p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.goals"></a>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" style="list-style-type: disc; "><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" type="1"><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"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.methods"></a>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"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.wrappers"></a>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="debug_mode_design.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"><div class="titlepage"><div><div><h5 class="title"><a id="debug_mode.design.methods.safe_iter"></a>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" style="list-style-type: disc; "><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"><div class="titlepage"><div><div><h5 class="title"><a id="debug_mode.design.methods.safe_seq"></a>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="debug_mode_design.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"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.precond"></a>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"><div class="titlepage"><div><div><h4 class="title"><a id="debug_mode.design.methods.coexistence"></a>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 use inline namespaces 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"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.compile"></a>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++11 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 |
| |
| inline namespace __debug { } |
| } |
| </pre></div><div class="section"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.link"></a>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" type="1"><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"><div class="titlepage"><div><div><h5 class="title"><a id="methods.coexistence.alt"></a>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" style="list-style-type: disc; "><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" target="_top">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" target="_top">proof-of-concept using 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"><div class="titlepage"><div><div><h3 class="title"><a id="debug_mode.design.other"></a>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" style="list-style-type: disc; "><li class="listitem"><p><a class="link" href="http://www.cs.sjsu.edu/faculty/horstman/safestl.html" target="_top">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/" target="_top">STLport</a>: STLport is a free |
| implementation of the C++ standard library derived from the <a class="link" href="https://web.archive.org/web/20171225062613/http://www.sgi.com/tech/stl/" target="_top">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 width="40%" align="left"><a accesskey="p" href="debug_mode_using.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="debug_mode.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="parallel_mode.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Using </td><td width="20%" align="center"><a accesskey="h" href="../index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 18. Parallel Mode</td></tr></table></div></body></html> |
