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Compiler-specific Features
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.
Restrictions
A function that is declared as pure can have no side effects. For example, pure functions:
• cannot call impure functions
• cannot use global variables or dereference pointers, because the compiler
assumes that the function does not access memory, except stack memory
• must return the same value each time when called twice with the same
parameters.
Example
int factr(int n) __pure
{
int f = 1;
while (n > 0)
f *= n--;
return f;}
See also
• __attribute__((const)) on page 4-33
• __pure on page 5-14 in the Compiler User Guide
• Placing ARM function qualifiers on page 5-16 in the Compiler User Guide.
4.1.13 __smc
The __smc keyword declares an SMC (Secure Monitor Call) function. A call to the SMC
function inserts an SMC instruction into the instruction stream generated by the compiler
at the point of function invocation.
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