#2660 pointer type incompatible with itself

[Philipp Klaus Krause]

In current SDCC, this code:

static int cmp_eq (long arg1, long arg2)
{
    return arg1 != arg2;
}

struct op {
    const char *op_name;
    void *op_func;
};

const struct op string_binop[] = {
    {"=", (void *)cmp_eq},
};

fails to compiler for z80 (and most likely theother backends, too):

test.c:12: error 129: pointer types incompatible 
from type 'void generic* fixed'
  to type 'void generic* fixed'

This pointer type incompatibility stuff has become a major issue. It prevents building of at least two OSes with SDCC: FUZIC and NuttX.

Philipp

[Philipp Klaus Krause]

Apparently, initValPointer() in SDCCglue.c returns 0, resulting in the error.

Philipp

P.S.: Or rather, the bug is that constExprValue() returns 0, even though is it supposed to return nonzero values for constant expressions (Iguess as identified by constExprTree() above).

[Philipp Klaus Krause]

By the C standard, we don't have to allow casts from pointers to functions to pointers to objects, so this bug seems to be not that big of an issue.

Philipp

[Philipp Klaus Krause]

However, one of the types reported in the error message is wrong, so even if we want to disallow such casts, there is still a bug here.

Philipp

[Philipp Klaus Krause]

As of revision [r10036], the fix for bug #2641 changed the error message. SDCC no longer claims that the pointer type is incompatible with itself, instead stating that the initializer is not a constant expression.
Ideally, if SDCC rejects the code it should complain about a pointer to a function type being cast to a pointer to an object type.

Philipp