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An additional issue is that readlink() can return -1 if it fails, causing an off-by-one underflow.

Compliant Solution

This example ensures there will be no overflow by only reading in sizeof(buf)-1 characters. It also properly checks to see if an error has occurred.

char buf[256];
ssizet_t len;

if ((len = readlink("/usr/bin/perl", buf, sizeof(buf)-1)) != -1)
    buf[len] = '\0';
else {
   /* handle error condition */
}

Risk Analysis

This is a fairly easy mistake to make. Fortunately the consequences are not that harsh, most likely resulting in abnormal program termination.

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