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Compiler-specific Features
4.4 Type attributes
The __attribute__ keyword enables you to specify special attributes of variables or
structure fields, functions, and types. The keyword format is either:
__attribute__ ((attribute1, attribute2, ...))
__attribute__ ((__attribute1__, __attribute2__, ...))
For example:
void * Function_Attributes_malloc_0(int b) __attribute__ ((malloc));
static int b __attribute__ ((__unused__));
Table 4-4 summarizes the available type attributes.
Table 4-4 Type attributes supported by the compiler and their equivalents
Type attribute
__attribute__((aligned))
__attribute__((packed))
non-attribute equivalent
__align
__packed a
__attribute__((transparent_union)) -
a. The __packed qualifier does not affect type in GNU mode.
4.4.1 __attribute__((aligned))
The aligned type attribute specifies a minimum alignment for the type.
Note
This type attribute is a GNU compiler extension that is supported by the ARM compiler.
4.4.2 __attribute((packed))
The packed type attribute specifies that a type must have the smallest possible alignment.
Note
This type attribute is a GNU compiler extension that is supported by the ARM compiler.
Errors
The compiler generates a warning message if you use this attribute in a typedef.
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