Default Type Promotions in Variadic Argument Lists
In C and C , variadic functions can accept a variable number of arguments. However, the compiler may need to perform implicit type promotions on these arguments to ensure compatibility with the function signature. This article examines the default type promotions that occur within variadic argument lists.
Default Integer Promotions
For functions without prototypes or arguments matching the ellipsis "...", C99 specifies that default argument promotions are applied. These include:
This means that the following code is valid even though uint8_t is an 8-bit unsigned integer and printf expects a 16-bit signed integer:
<code class="c">uint8_t a = 5; printf("%d", a);</code>
Float Promotion
In addition to default integer promotions, float arguments are promoted to double in variadic contexts. This ensures compatibility with functions expecting double arguments, such as printf's %f format specifier.
Other Analogous Types
The same default promotion rules apply to other analogous types:
Implications
These default promotions ensure that arguments passed to variadic functions are compatible with the function signature. However, it is important to be aware of the potential implications:
By understanding the default type promotions in variadic argument lists, programmers can use these functions safely and effectively.
The above is the detailed content of How Do Default Type Promotions Work in Variadic Argument Lists in C and C ?. For more information, please follow other related articles on the PHP Chinese website!