[Bug c++/105020] New: #pragma GCC diagnostic ignored "-Wmultichar" doesn't work

[Bug c++/105020] New: #pragma GCC diagnostic ignored "-Wmultichar" doesn't work

[andre.schackier at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105020

            Bug ID: 105020
           Summary: #pragma GCC diagnostic ignored "-Wmultichar" doesn't
                    work
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: andre.schackier at gmail dot com
  Target Milestone: ---

Created attachment 52664
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52664&action=edit
The used source code

Give the following source code:

```cpp
#pragma GCC diagnostic ignored "-Wmultichar"
#pragma GCC diagnostic ignored "-Woverflow"

void EnterCharacter(unsigned short);

int main() { EnterCharacter('\0xFF'); }
```

Produces the following output:
```
source>:6:29: warning: multi-character character constant [-Wmultichar]
    6 | int main() { EnterCharacter('\0xFF'); }
      |                             ^~~~~~~
```

It seems all version from gcc-4.6.4 to gcc-11.2 are affected including trunk.

[godbolt link](https://godbolt.org/z/PTWPModPT)

[Bug c++/105020] #pragma GCC diagnostic ignored "-Wmultichar" doesn't work

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105020

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
There might be a dup of this bug but basically the issue is the c++ does lexing
up front and the pragma is handled in frontend after lexing.

[Bug c++/105020] #pragma GCC diagnostic ignored "-Wmultichar" doesn't work

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105020

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 53431 (well it is a dup of bug 100891 which was marked as a dup of
that other bug).

*** This bug has been marked as a duplicate of bug 53431 ***