https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92158
--- Comment #4 from Jonny Grant <jg at jguk dot org> ---
Hello
Implicit conversion can introduce bugs. I would like to detect implicit enum
conversions to other types in C and C++. How about just adding the C++ warnings
first to match clang in example below?
The following example does produce warnings in C++ with Clang trunk, but not C.
Likewise with MSVC, C++ warning, but no C warning.
G++ only warns on line (19), clang has the additional line (15) and line (17)
warnings.
Could G++ also add the additions warnings?
-O2 -Wall -Wextra -Wconversion -Werror
#include <stdio.h>
typedef enum
{
a = -1
} a_t;
a_t f()
{
return a;
}
int main()
{
unsigned int b = f();
a_t test = b;
printf("%u %u", test, b);
return b;
}
#1 with x86-64 clang (trunk)
<source>:15:22: error: implicit conversion changes signedness: 'a_t' to
'unsigned int' [-Werror,-Wsign-conversion]
unsigned int b = f();
~ ^~~
<source>:17:9: error: cannot initialize a variable of type 'a_t' with an lvalue
of type 'unsigned int'
a_t test = b;
^ ~
<source>:19:12: error: implicit conversion changes signedness: 'unsigned int'
to 'int' [-Werror,-Wsign-conversion]
return b;
~~~~~~ ^
3 errors generated.
Compiler returned: 1
#1 with x64 msvc v19.22
example.cpp
<source>(18): error C2440: 'initializing': cannot convert from 'unsigned int'
to 'a_t'
<source>(18): note: Conversion to enumeration type requires an explicit cast
(static_cast, C-style cast or function-style cast)
Compiler returned: 2
x86-64 gcc (trunk) - 484ms
#1 with x86-64 gcc (trunk)
<source>: In function 'int main()':
<source>:17:16: error: invalid conversion from 'unsigned int' to 'a_t'
[-fpermissive]
17 | a_t test = b;
| ^
| |
| unsigned int
Compiler returned: 1
