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copied!<p>At least from your description, you only care about sorting on PRI values, but want the negative values to come after positive ones (but the positive ones to be in order).</p> <p>One easy way to do this is to cast the PRI values to unsigned before doing the comparison. When converted to unsigned, a negative value will be reduced modulo 2<sup>N</sup>-1 so (for example) -1 will convert to UINT_MAX (and, more importantly, all negative numbers will convert to unsigned numbers greater than anything that started out as a positive signed number).</p> <pre><code>typedef struct { int PID; int PRI; } proc; int cmp(void const *a, void const *b) { proc const *aa = (proc const *)a; proc const *bb = (proc const *)b; if ((unsigned)(bb->PRI) < (unsigned)(aa->PRI)) return -1; if ((unsigned)(aa->PRI) < (unsigned)(bb->PRI)) return 1; return 0; } </code></pre> <p>At the end, instead of returning 0 based only on equality of the PRI values, you may also want to add a comparison of the PIDs, so items will equal PRI values will be sorted by PID. I've left that out for now, since you haven't said that you really need/want it (and it makes the code a bit longer and potentially harder to understand, especially if you're not expecting it to be there).</p> <p>Edit: In case it wasn't clear, this comparison function is intended to work with <code>qsort</code>, and (assuming you do the comparison correctly) a stable sort isn't necessary. You only need a stable sort if you decided go the (nearly always slower) route of sorting first on one field, then doing a second (separate) sort on a second field, rather than comparing on all the relevant fields in a single comparison.</p>

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