[Bug c++/111174] New: G++ allows re-declaring function parameters as functions

[janschultke at googlemail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111174

            Bug ID: 111174
           Summary: G++ allows re-declaring function parameters as
                    functions
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: janschultke at googlemail dot com
  Target Milestone: ---

## Code to Reproduce

void foo(int x) {
    void x(int);
}


## Expected Output

The expected output is emitted in C mode, and also by clang in C/C++ mode
(https://godbolt.org/z/b8Gbj69Kn)

<source>: In function 'foo':
<source>:2:10: error: 'x' redeclared as different kind of symbol
    2 |     void x(int);
      |          ^
<source>:1:14: note: previous definition of 'x' with type 'int'
    1 | void foo(int x) {
      |          ~~~~^

## Actual Output (only in C++ mode)

Compiles.


## Explanation

There is no wording in the standard that allows function declarations to
redeclare function parameters. This erroneous behavior only occurs for
redeclaring function parameters; local/global variables seem unaffected.