| Issue |
63315
|
| Summary |
clang re-enables explicitly disabled diagnostics which are more specific members of a group when that group's diagnostics are enabled
|
| Labels |
clang:driver
|
| Assignees |
|
| Reporter |
nickdesaulniers
|
Consider `-Wunused`, which itself is a group containing many sub-warnings, such as `-Wunused-but-set-variable`, and the following example code:
```c++
void foo (void) {
int y;
y = 0;
}
```
If you compile this with ` -Wno-unused-but-set-variable -Wunused` GCC does not warn, but clang does. In fact, [GCC documents this behavior](https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html):
> Some options, such as -Wall and -Wextra, turn on other options, such as -Wunused, which may turn on further options, such as -Wunused-value. The combined effect of positive and negative forms is that more specific options have priority over less specific ones, independently of their position in the command-line.
The end effect of this difference is that [it makes disabling warnings portably across toolchains more difficult](https://lore.kernel.org/llvm/[email protected]/).
IIRC, clang re-enables all of the subgroups of `-Wunused`, without first checking whether any of the subgroups were previously explicitly disabled. Is this a known issue (I wasn't able to find a pre-existing bug report)?
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