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"It is undefined what will happen if a pointer of some type is converted to void*, and then the void\* pointer is converted to a type with a stricter alignment requirement" \-C99 rationaleV5.10.pdf |
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h2. Non-compliant code example |
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{code | ||
:bgColor | =#FFCCCC | } char *char_ptr = "example"; int *int_ptr; int *Function(void *v_pointer){ return pointer; } P2 = Function(pointer); {code} Pointer might be aligned on even boundary, once it is cast to an int some architectures will require it to be on 4 byte boundaries. Pointers are often cast because a void\* cannot be dereferenced. Careless coding can result in an arbitrary pointer type being used irregardless of its alignment. |
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List of common alignments for Microsoft, Borland and GNU compilers to x86 |
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char \-1 byte aligned |
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short \-2 byte aligned |
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int \-4 byte aligned |
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float - 4 byte aligned |
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double - 8 byte on windows, 4 byte on linux |
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h2. Compliant code suggestions |
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{code | ||
:bgColor | =#ccccff | }
-make specific functions (avoid use of void*)
-always use strictest alignment type for arbitary pointers
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Risk Assessment
Programs can crash
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
DRAFT | 1 (low) | 2 (probable) | 2 (medium) | P4 | L3 |
References
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{code} h2. Risk Assessment Programs can crash || Rule || Severity || Likelihood || Remediation Cost || Priority || Level || | DRAFT | *1* (low) | *2* (probable) | *2* (medium) | {color:green}P4{color} | {color:green}L3{color} | h2. References {list} \*Bryant, Randal and O'Hallaron, David. [2003] 2001 Computer Systems: A Programmer's Perspective. Prentice Hall. ISBN 0-13-034074-X. |
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\*[http://www.open-std.org/jtc1/sc22/wg14/www/C99RationaleV5.10.pdf |
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