4e0e265d9e
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63 lines
2.4 KiB
Plaintext
63 lines
2.4 KiB
Plaintext
== Why is this an issue?
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The ``++sizeof++`` operator returns the size, in bytes, of its operand, which can be an expression or a type.
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Function parameters with array types automatically decay to pointers, so it is hazardous to call the ``++sizeof++`` operator on such variables.
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Moreover, calling the ``++sizeof++`` operator on a variable with pointer type is typically a mistake. Usually the intent was to get the size of the pointed-to value instead.
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=== Noncompliant code example
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[source,text]
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----
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void clear1(int array[]) {
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for (size_t i = 0; i < sizeof(array) / sizeof(*array); i+=1) { // Noncompliant, type of array decays to int *, so sizeof(array) evaluates to sizeof(int *)
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array[i] = 0;
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}
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}
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void clear2(short *array, int count) {
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memset(array, sizeof(array) * count); // Noncompliant, sizeof(array) evaluates to the size of a pointer to short and not of a short
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}
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----
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== Resources
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* CWE - https://cwe.mitre.org/data/definitions/467[CWE-467 - Use of sizeof() on a Pointer Type]
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ifdef::env-github,rspecator-view[]
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'''
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== Comments And Links
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(visible only on this page)
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=== on 10 Feb 2015, 13:48:04 Samuel Mercier wrote:
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\[~evgeny.mandrikov] I rewrote the rule to prevent usage of ``++sizeof++`` on a variable with pointer type
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\[~ann.campbell.2] Could you verify?
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=== on 10 Feb 2015, 13:55:58 Ann Campbell wrote:
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I've made some updates [~samuel.mercier] that you probably want to check. Since this is not a MISRA rule, then we should use the standard format for the title: "X should [not] y", rather than using "shall".
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Also, I'm not wild about the message. I'd either go with "Remove this use of..." or '"x" is a pointer'.
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=== on 13 Feb 2015, 08:44:14 Samuel Mercier wrote:
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\[~ann.campbell.2] ok for title. For the message, in past, we already had this discussion :) '"x" is a pointer' doesn't say anything about neither the problem nor the resolution, so it should be avoided. I also don't really like the "remove" form because there are really two cases covered by this rule:
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1) sizeof is used on a function parameter with type array. in that case sizeof should effectively be removed and an additional size argument must be provided
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2) sizeof is probably badly used on a pointer, so there is probably a missing * : sizeof(p) -> sizeof(*p)
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so among the three I would stick with the current one.
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=== on 13 Feb 2015, 12:20:36 Ann Campbell wrote:
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Okay [~samuel.mercier]
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endif::env-github,rspecator-view[]
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