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| <h5 class="subsubsection">3.2.3.2 Example program excerpts</h5> |
| |
| <p>Even though the tracing functionality does not influence the runtime |
| behavior of the program it is not a good idea to call <code>mtrace</code> in |
| all programs. Just imagine that you debug a program using <code>mtrace</code> |
| and all other programs used in the debugging session also trace their |
| <code>malloc</code> calls. The output file would be the same for all programs |
| and thus is unusable. Therefore one should call <code>mtrace</code> only if |
| compiled for debugging. A program could therefore start like this: |
| |
| <pre class="example"> #include <mcheck.h> |
| |
| int |
| main (int argc, char *argv[]) |
| { |
| #ifdef DEBUGGING |
| mtrace (); |
| #endif |
| ... |
| } |
| </pre> |
| <p>This is all what is needed if you want to trace the calls during the |
| whole runtime of the program. Alternatively you can stop the tracing at |
| any time with a call to <code>muntrace</code>. It is even possible to restart |
| the tracing again with a new call to <code>mtrace</code>. But this can cause |
| unreliable results since there may be calls of the functions which are |
| not called. Please note that not only the application uses the traced |
| functions, also libraries (including the C library itself) use these |
| functions. |
| |
| <p>This last point is also why it is no good idea to call <code>muntrace</code> |
| before the program terminated. The libraries are informed about the |
| termination of the program only after the program returns from |
| <code>main</code> or calls <code>exit</code> and so cannot free the memory they use |
| before this time. |
| |
| <p>So the best thing one can do is to call <code>mtrace</code> as the very first |
| function in the program and never call <code>muntrace</code>. So the program |
| traces almost all uses of the <code>malloc</code> functions (except those |
| calls which are executed by constructors of the program or used |
| libraries). |
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