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Default Type Promotions in Variadic Argument Lists
In C and C , when passing arguments to a function with a variable number of arguments (i.e., a variadic function), certain default type promotions occur.
Integer Promotion
The C and C standards guarantee that any integer type with a rank less than int is promoted to either int or unsigned int. This means that if you pass an 8-bit integer (e.g., uint8_t) to a function that expects int (which is typically 16 bits or more in size), the 8-bit integer will be automatically promoted to 16 bits or larger.
For example, in the provided code snippet:
uint8_t a = 5; printf("%d", a);
The format specifier %d expects an int, but since a is a uint8_t, it will be promoted to int before being passed to printf.
Float Promotion
Similarly, float values are promoted to double by default. This means that if you pass a float to a function that expects a double, the float will be automatically converted to double precision.
Example
In summary, the default type promotions in variadic argument lists are:
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