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From: "gcc at emil dot codes" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/105180] New: K&R style definition does not evaluate array size
Date: Wed, 06 Apr 2022 14:33:51 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105180

            Bug ID: 105180
           Summary: K&R style definition does not evaluate array size
           Product: gcc
           Version: 11.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc at emil dot codes
  Target Milestone: ---

GCC doesn't evaluates the size of an array when declared as a parameter in =
K&R
style declaration.


Example program:

    #include <stdio.h>

    int crime(s, c)
        char *s;
        char c[static printf("%s\n", s)];
    {
        return 0;
    }

    int accomplice(s) char *s;
    {
        return crime(s, s);
    }

    int main(void)
    {
        return accomplice("Hello");
    }

This should print "Hello\n". When using an ANSI definition, it does, but in
K&R-style, nothing is printed, `printf` isn't evaluated at all.

According to godbolt's compiler explorer, it is a regression which appeared
after GCC 4.6.4 and before or in GCC 4.7.1
It works correctly in clang but not in modern GCC.=