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| <h4 class="subsection">15.3.1 An Overview of Type Checking</h4> |
| |
| <p>Some languages, such as C and C<tt>++</tt>, are strongly typed, meaning that the |
| arguments to operators and functions have to be of the correct type, |
| otherwise an error occurs. These checks prevent type mismatch |
| errors from ever causing any run-time problems. For example, |
| |
| <pre class="smallexample"> int klass::my_method(char *b) { return b ? 1 : 2; } |
| |
| (gdb) print obj.my_method (0) |
| $1 = 2 |
| <br>but<br> |
| (gdb) print obj.my_method (0x1234) |
| Cannot resolve method klass::my_method to any overloaded instance |
| </pre> |
| <p>The second example fails because in C<tt>++</tt> the integer constant |
| ‘<samp><span class="samp">0x1234</span></samp>’ is not type-compatible with the pointer parameter type. |
| |
| <p>For the expressions you use in <span class="sc">gdb</span> commands, you can tell |
| <span class="sc">gdb</span> to not enforce strict type checking or |
| to treat any mismatches as errors and abandon the expression; |
| When type checking is disabled, <span class="sc">gdb</span> successfully evaluates |
| expressions like the second example above. |
| |
| <p>Even if type checking is off, there may be other reasons |
| related to type that prevent <span class="sc">gdb</span> from evaluating an expression. |
| For instance, <span class="sc">gdb</span> does not know how to add an <code>int</code> and |
| a <code>struct foo</code>. These particular type errors have nothing to do |
| with the language in use and usually arise from expressions which make |
| little sense to evaluate anyway. |
| |
| <p><span class="sc">gdb</span> provides some additional commands for controlling type checking: |
| |
| <p><a name="index-set-check-type-975"></a><a name="index-show-check-type-976"></a> |
| <dl> |
| <dt><code>set check type on</code><dt><code>set check type off</code><dd>Set strict type checking on or off. If any type mismatches occur in |
| evaluating an expression while type checking is on, <span class="sc">gdb</span> prints a |
| message and aborts evaluation of the expression. |
| |
| <br><dt><code>show check type</code><dd>Show the current setting of type checking and whether <span class="sc">gdb</span> |
| is enforcing strict type checking rules. |
| </dl> |
| |
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