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Non-Compliant Code Example (Ints vs. Floats)
The following non-compliant code demonstrates the perils of operating on data of improper types. It tries to increment an int typecast as a float, and a float typecast as an int, and displays the results.
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Compliant Solution (Ints vs. Floats)
Here In this compliant solution, the pointers are assigned to the variables of the proper data types.
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Bit-fields can be used to allow flags or other integer values with small ranges to be packed together to save storage space. Bit-fields can improve the storage efficiency of structures. Compilers typically allocate consecutive bit-field structure members into the same int-sized storage, as long as they fit completely into that storage unit. However, the order of allocation within a storage unit is implementation-defined. Some implementations are "right-to-left": the first member occupies the low-order position of the storage unit. Others are "left-to-right": the first member occupies the high-order position of the storage unit. Calculations that depend on the order of bits within a storage unit may produce different results on different implementations.
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Non-Compliant Code Example (Bit-Field Overlap)
In this the following non-compliant examplecode, assuming eight bits to a byte, if bit-fields of six and four bits are declared, is each bit-field contained within a byte or are the bit-fields split across multiple bytes?
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struct bf {
unsigned int m1 : 6;
unsigned int m2 : 4;
};
void function() {
unsigned char *ptr;
struct bf data;
data.m1 = 0;
data.m2 = 0;
ptr = (unsigned char *)&data;
ptr++;
*ptr += 1; /* what does this increment? */
}
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In the above example, if If each bit-field lives within its own byte, then m2 (or m1, depending on alignment) is incremented by 1. If the bit-fields are indeed packed across 8-bit bytes, then m2 might be incremented by 4.
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