V734. An excessive expression. Examine the substrings "abc" and "abcd".

The analyzer detected a potential bug, connected with the fact that a longer and shorter substrings are searched in the expression. With all that a shorter string is a part of a longer one. As a result, one of the comparisons is redundant or there is a bug here.

Consider the following example:

if (strstr(a, "abc") != NULL || strstr(a, "abcd") != NULL)

If substring "abc" is found, the check will not execute any further. If substring "abc" is not found, then searching for longer substring "abcd" does not make sense either.

To fix this error, we need to make sure that the substrings were defined correctly or delete extra checks, for example:

if (strstr(a, "abc") != NULL)

Here's another example:

if (strstr(a, "abc") != NULL)
else if (strstr(a, "abcd") != NULL)

In this code, function Foo2() will never be called. We can fix the error by reversing the check order to make the program search for the longer substring first and then search for the shorter one:

if (strstr(a, "abcd") != NULL)
else if (strstr(a, "abc") != NULL)

You can look at examples of errors detected by the V734 diagnostic.

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