#872 broken boolean bitfield runtime assignments from unsigned values

[dkl]

It looks like saving a non-zero value from an unsigned variable/expression into a boolean bitfield will result in 0/false, while it should be -1/true.

type UDT
    a : 1 as boolean
    b : 1 as boolean
    c : 1 as boolean
end type

#macro test(assignment)
    scope
        dim x as UDT
        assignment
        print x.a, x.b, x.c
    end scope
#endmacro

scope
    test(x.a = 1u)
    test(x.b = 1u)
    test(x.c = 1u)
end scope

print "---"
scope
    dim value as uinteger = 1
    test(x.a = value)
    test(x.b = value)
    test(x.c = value)
end scope

[munair]

In your example, a, b and c are not booleans. They are integers. The following code works as expected:

type UDT
  a as boolean = 1u
  b as boolean = 1
  c as boolean = -1
end type

dim x as UDT
dim as uinteger value = 1

print x.a, x.b, x.c
x.a = value
print x.a

[munair]

At best, one could say that the demonstrated code "a: 1 as boolean" (sort of an implicit bitfied) results in unpredictable behaviour. It shouldn't be allowed in my opinion. When inserting integers in-between, the results are "correct":

type UDT
  a: 1 as boolean
  aa as integer
  b: 1 as boolean
  bb as integer
  c: 1 as boolean
  cc as integer
end type

dim x as UDT
dim value as uinteger = 1
x.a = value
print x.a
x.b = value
print x.b
x.c = value
print x.c

Remark: tested with FBC 1.06

[Jeff Marshall]

Internally, fbc handles the bitfields as FB_DATATYPE_UINT and conversion to BOOLEAN is getting optimized out prematurely.

diff --git a/src/compiler/ast-node-misc.bas b/src/compiler/ast-node-misc.bas
index 04a9321fa..ce030c973 100644
--- a/src/compiler/ast-node-misc.bas
+++ b/src/compiler/ast-node-misc.bas
@@ -433,6 +433,10 @@ private function astSetBitfield _
    if( symbGetType( bitfield ) = FB_DATATYPE_BOOLEAN ) then
        if( r->class <> AST_NODECLASS_CONV ) then
            r = astNewCONV( FB_DATATYPE_BOOLEAN, NULL, r )

+       else
+           if( astGetFullType( r ) <> FB_DATATYPE_BOOLEAN ) then
+               r = astNewCONV( FB_DATATYPE_BOOLEAN, NULL, r )
+           end if
        end if
        r = astNewCONV( FB_DATATYPE_UINT, NULL, r )
        r = astNewBOP( AST_OP_AND, r, hMakeUintMask( bitfield->var_.bits, bitfield->var_.bitpos ) )

What is method to handle bugs? branch, fix, update changelog, pull request? Then if accepted, close this ticket?

[Jeff Marshall]

Fixed at
https://sourceforge.net/p/fbc/code/ci/c9bf95db7a87709e68597ae9bf5df287f4902fa6/tree/