[Bug c++/114006] New: False positive diagnostic -Wpedantic for zero-size arrays, most vexing parse

["janschultke at googlemail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114006

            Bug ID: 114006
           Summary: False positive diagnostic -Wpedantic for zero-size
                    arrays, most vexing parse
           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: ---

I got a false positive warning when compiling LLVM with g++. Here is a minimal
repro:

struct string {
    const char* data;
    string operator+(const char*);
};

int LLVMFuzzerInitialize(int*, char***argv) {
    string ExitOnErr(string(*argv[0]) + ": error:");
    return 0;
}



<source>: In function 'int LLVMFuzzerInitialize(int*, char***)':
<source>:7:35: warning: ISO C++ forbids zero-size array 'argv' [-Wpedantic]
    7 |     string ExitOnErr(string(*argv[0]) + ": error:");
      |



It looks like GCC thinks that this is a most vexing parse; i.e. it thinks that
argv[0] is a declarator, not a subscript operator. This cannot be correct
because the next expression is + ": error" so this cannot be parsed as a
function declaration.

I suspect that the diagnostic for zero-size arrays is prematurely emitted,
before it's actually known whether this is a function declaration or not.