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| Next: <a href="C-Defaults.html#C-Defaults" accesskey="n" rel="next">C Defaults</a>, Previous: <a href="C-Constants.html#C-Constants" accesskey="p" rel="prev">C Constants</a>, Up: <a href="C.html#C" accesskey="u" rel="up">C</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="C_002b_002b-Expressions"></a> |
| <h4 class="subsubsection">15.4.1.3 C<tt>++</tt> Expressions</h4> |
| |
| <a name="index-expressions-in-C_002b_002b"></a> |
| <p><small>GDB</small> expression handling can interpret most C<tt>++</tt> expressions. |
| </p> |
| <a name="index-debugging-C_002b_002b-programs"></a> |
| <a name="index-C_002b_002b-compilers"></a> |
| <a name="index-debug-formats-and-C_002b_002b"></a> |
| <a name="index-GCC-and-C_002b_002b"></a> |
| <blockquote> |
| <p><em>Warning:</em> <small>GDB</small> can only debug C<tt>++</tt> code if you use |
| the proper compiler and the proper debug format. Currently, |
| <small>GDB</small> works best when debugging C<tt>++</tt> code that is compiled |
| with the most recent version of <small>GCC</small> possible. The DWARF |
| debugging format is preferred; <small>GCC</small> defaults to this on most |
| popular platforms. Other compilers and/or debug formats are likely to |
| work badly or not at all when using <small>GDB</small> to debug C<tt>++</tt> |
| code. See <a href="Compilation.html#Compilation">Compilation</a>. |
| </p></blockquote> |
| |
| <ol> |
| <li> <a name="index-member-functions"></a> |
| Member function calls are allowed; you can use expressions like |
| |
| <div class="smallexample"> |
| <pre class="smallexample">count = aml->GetOriginal(x, y) |
| </pre></div> |
| |
| </li><li> <a name="index-this_002c-inside-C_002b_002b-member-functions"></a> |
| <a name="index-namespace-in-C_002b_002b"></a> |
| While a member function is active (in the selected stack frame), your |
| expressions have the same namespace available as the member function; |
| that is, <small>GDB</small> allows implicit references to the class instance |
| pointer <code>this</code> following the same rules as C<tt>++</tt>. <code>using</code> |
| declarations in the current scope are also respected by <small>GDB</small>. |
| |
| </li><li> <a name="index-call-overloaded-functions"></a> |
| <a name="index-overloaded-functions_002c-calling"></a> |
| <a name="index-type-conversions-in-C_002b_002b"></a> |
| You can call overloaded functions; <small>GDB</small> resolves the function |
| call to the right definition, with some restrictions. <small>GDB</small> does not |
| perform overload resolution involving user-defined type conversions, |
| calls to constructors, or instantiations of templates that do not exist |
| in the program. It also cannot handle ellipsis argument lists or |
| default arguments. |
| |
| <p>It does perform integral conversions and promotions, floating-point |
| promotions, arithmetic conversions, pointer conversions, conversions of |
| class objects to base classes, and standard conversions such as those of |
| functions or arrays to pointers; it requires an exact match on the |
| number of function arguments. |
| </p> |
| <p>Overload resolution is always performed, unless you have specified |
| <code>set overload-resolution off</code>. See <a href="Debugging-C-Plus-Plus.html#Debugging-C-Plus-Plus"><small>GDB</small> Features for C<tt>++</tt></a>. |
| </p> |
| <p>You must specify <code>set overload-resolution off</code> in order to use an |
| explicit function signature to call an overloaded function, as in |
| </p><div class="smallexample"> |
| <pre class="smallexample">p 'foo(char,int)'('x', 13) |
| </pre></div> |
| |
| <p>The <small>GDB</small> command-completion facility can simplify this; |
| see <a href="Completion.html#Completion">Command Completion</a>. |
| </p> |
| </li><li> <a name="index-reference-declarations"></a> |
| <small>GDB</small> understands variables declared as C<tt>++</tt> references; you can use |
| them in expressions just as you do in C<tt>++</tt> source—they are automatically |
| dereferenced. |
| |
| <p>In the parameter list shown when <small>GDB</small> displays a frame, the values of |
| reference variables are not displayed (unlike other variables); this |
| avoids clutter, since references are often used for large structures. |
| The <em>address</em> of a reference variable is always shown, unless |
| you have specified ‘<samp>set print address off</samp>’. |
| </p> |
| </li><li> <small>GDB</small> supports the C<tt>++</tt> name resolution operator <code>::</code>—your |
| expressions can use it just as expressions in your program do. Since |
| one scope may be defined in another, you can use <code>::</code> repeatedly if |
| necessary, for example in an expression like |
| ‘<samp><var>scope1</var>::<var>scope2</var>::<var>name</var></samp>’. <small>GDB</small> also allows |
| resolving name scope by reference to source files, in both C and C<tt>++</tt> |
| debugging (see <a href="Variables.html#Variables">Program Variables</a>). |
| |
| </li><li> <small>GDB</small> performs argument-dependent lookup, following the C<tt>++</tt> |
| specification. |
| </li></ol> |
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