[Swig-cvs] [swig/swig] a28b8c: Redundant code removal in nested.cxx

[William S F. <no...@gi...>]

  Branch: refs/heads/master
  Home:   https://github.com/swig/swig
  Commit: a28b8cfed4ed09eee17ade562bd112cf02717673
      https://github.com/swig/swig/commit/a28b8cfed4ed09eee17ade562bd112cf02717673
  Author: William S Fulton <ws...@fu...>
  Date:   2023-09-10 (Sun, 10 Sep 2023)

  Changed paths:
    M Source/Modules/nested.cxx

  Log Message:
  -----------
  Redundant code removal in nested.cxx

c96c04c5aef0a3d2aa9c12da4bafff0053fca482
Replicate changes in this commit to add_symbols() for add_symbols_c().
Setting feature:immutable is now done in Allocate:cDeclaration.
Setting hasconsttype for static const variables (or constexpr) doesn't
look possible in this situation (C code for anonymous structs) - no
valid C syntax that I can figure out.

Anonymous nested structs are necessarily read-only (and set as
immutable in Swig_nested_name_unnamed_c_structs).

>From https://sourceforge.net/p/swig/bugs/793/ ...

The union variable intRep below has a named type IntRepType.

typedef struct Object {
  int objtype;
  union IntRepType {
    double dvalue;
  } intRep;
} Object;

void tester() {
  /* approach (1) */
  obj.intRep.dvalue = 1.23;

  /* approach (2) */
  union IntRepType irt;
  irt.dvalue = 2.34;
  obj.intRep = irt;
}

Using C code there are two approaches to setting a value in intRep. Equivalents in perl are:

my $obj = example::Object->new();

 # approach (1)
$obj->{intRep}->{dvalue} = 3.45;

 # approach (2)
my $irt = example::IntRepType->new();
$irt->{dvalue} = 4.56;
$obj->{intRep} = $irt;

An Object_intRep_set wrapper is generated which takes type IntRepType as desired.

However, with an anonymous union:

typedef struct Object {
  int objtype;
  union IntRepType {
    double dvalue;
  } intRep;
} Object;

intRep does not have any named type name and is anonymous. It is thus not possible to create a type outside of Object to assign to intRep.
Only approach (1) is available in C and so SWIG can only provide approach (1) via wrappers too.
There is no Object_intRep_set wrapper, intRep is immutable.