False positive [constVariable] when a two-dimensional array is written to through an array of pointers

[Siim Ainsaar]

I analyzed the following file.

void f(void)
{
    char a[1][1];
    char *b[1];
    b[0] = a[0];
    **b = 0;
}

cppcheck 2.8 and also the current tip of the main branch give the following false error:

$ cppcheck --enable=style --debug t.c 
Checking t.c ...


##file t.c
1: void f ( )
2: {
3: char a@var1 [@expr3 1 ] [@expr4 1 ] ;
4: char * b@var2 [@expr5 1 ] ;
5: b@var2 [@expr6 0 ] =@expr7 a@var1 [@expr8 0 ] ;
6: *@expr9 *@expr10 b@var2 =@expr11 0 ;
7: }



##Value flow
Line 3
  1 always 1
  1 always 1
Line 4
  1 always 1
Line 5
  b {lifetime[Object]=(b),Uninit*}
  0 always 0
  a {lifetime[Object]=(a),Uninit**}
  0 always 0
Line 6
  b possible lifetime[Object]=(b)
  = always 0
  0 always 0
t.c:3:10: style: Variable 'a' can be declared as const array [constVariable]
    char a[1][1];
         ^

As **b points at the first element of a, we're obviously writing there, therefore it would be incorrect to put a into read-only memory. If I try to mark a as const char a[1][1], then cppcheck doesn't warn, but gcc rightfully does.

Interestingly the false warning disappears if I initialize b on the same line as char *b[1] = {a[0]};

[CHR]

Thanks for reporting, this PR fixes the issue: https://github.com/danmar/cppcheck/pull/4228