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Compiler-specific Features
short x;
char y;
__packed int z;
// only pack this field
char a;
} Y; // 8 byte structure, natural alignment = 2
int g(Y *p)
{
return p->z + p->x;
}
// only unaligned read for z
See also
• __attribute__((packed)) on page 4-44
• Packed structures on page 5-10
• The __packed qualifier and unaligned accesses to data on page 4-24 in the
Compiler User Guide
• __packed structures versus individually __packed fields on page 4-26 in the
Compiler User Guide.
4.1.12 __pure
The __pure keyword asserts that a function declaration is pure.
A function is pure only if:
• the result depends exclusively on the values of its arguments
• the function has no side effects.
__pure is a function qualifier. It affects the type of a function.
Note
This keyword has the function attribute equivalent __attribute__((const)).
Default
By default, functions are assumed to be impure.
Usage
Pure functions are candidates for common subexpression elimination.
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