[Bug c/101289] New: bogus -Wvla-paramater warning when using const for vla param

[ljrk at ljrk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101289

            Bug ID: 101289
           Summary: bogus -Wvla-paramater warning when using const for vla
                    param
           Product: gcc
           Version: 11.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ljrk at ljrk dot org
  Target Milestone: ---

Created attachment 51099
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51099&action=edit
minimum working/reproducing example

If the vla parameter has a const specifier, the compiler will warn about
mismatched bounds:

$ cat mwe.c && make CFLAGS=-Wvla-parameter mwe.o     
extern void mwe(const int len, char buf[len]);
void mwe(const int len, char buf[len]) {}
cc -Wvla-parameter   -c -o mwe.o mwe.c
mwe.c:2:30: warning: argument 2 of type ‘char[len]’ declared with mismatched
bound ‘len’ [-Wvla-parameter]
    2 | void mwe(const int len, char buf[len]) {}
      |                         ~~~~~^~~~~~~~
mwe.c:1:37: note: previously declared as ‘char[len]’ with bound ‘len’
    1 | extern void mwe(const int len, char buf[len]);
      |                                ~~~~~^~~~~~~~
$

If I remove the const specifier to len, the warning goes away:

$ sed 's/const //g' -i mwe.c && make CFLAGS=-Wvla-parameter mwe.o  
cc -Wvla-parameter   -c -o mwe.o mwe.c
$

Maybe this is related to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97548 ?