https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83151
Bug ID: 83151
Summary: Explicit unsigned bitfields are treated as signed ones
Product: gcc
Version: 7.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: lh_mouse at 126 dot com
Target Milestone: ---
Minimal testcase:
```c
struct foo {
unsigned bf : 6;
};
unsigned get(const struct foo *ptr){
return ~ptr->bf;
}
```
```
E:\Desktop>gcc -c test.c -Wall -Wextra -Wsign-conversion -Werror
test.c: In function 'get':
test.c:6:10: error: conversion to 'unsigned int' from 'int' may change the sign
of the result [-Werror=sign-conversion]
return ~ptr->bf;
^~~~~~~~
cc1.exe: all warnings being treated as errors
```
GCC manual says
> -fsigned-bitfields
> -funsigned-bitfields
> -fno-signed-bitfields
> -fno-unsigned-bitfields
> These options control whether a bit-feld is signed or unsigned, when the
> declaration does not use either signed or unsigned. By default, such a
> bit-feld is
> signed, because this is consistent: the basic integer types such as int are
> signed
> types.
but it looks certainly incorrect if an explicit `unsigned` is specified.
