| Issue |
87641
|
| Summary |
Incorrect behavior when promoting bit-field of bit-precise type
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Halalaluyafail3
|
Clang promotes to the incorrect type when applying integer promotions to bit-fields of bit-precise type, for example:
```c
#include<stdio.h>
int main(void){
puts(_Generic(
+(struct{unsigned _BitInt(7)x:2;}){}.x,
unsigned _BitInt(2):"A",unsigned _BitInt(7):"B",int:"C"
));
}
```
This program should output "B", but clang outputs "C".
> The value from a bit-field of a bit-precise integer type is converted to the corresponding bit-precise
integer type. If the original type is not a bit-precise integer type (6.2.5): if an int can represent all
values of the original type (as restricted by the width, for a bit-field), the value is converted to an
int; otherwise, it is converted to an unsigned int. These are called the integer promotions. All
other types are unchanged by the integer promotions
>
> (footnote) E.g. unsigned _BitInt(7): 2 is a bit-field that can hold the values 0, 1, 2, 3, and converts to unsigned _BitInt(7).
The promoted type of `unsigned _BitInt(7)x:2` isn't `int`, it should be `unsigned _BitInt(7)` as the footnote says.
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