#1276 %new_copy may generate invalid C++

[Anonymous]

Generated code
static uint8* *copy_uint8pp(uint8* value) {
return (new uint8*(static_cast< const uint8*& >(value)));
}
is invalid (clang error):
error: non-const lvalue reference to type 'const uint8 *' (aka 'const unsigned char *') cannot bind to a value of unrelated type 'uint8 *' (aka 'unsigned char *')
return (new uint8*(static_cast< const uint8*& >(value)));
^ ~~~~~
error: cannot initialize a new value of type 'uint8 *' (aka 'unsigned char *') with an lvalue of type 'const uint8 *' (aka 'const unsigned char *')
return (new uint8*(static_cast< const uint8*& >(value)));
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2 errors generated.

called from cpointer.i:
%define %pointer_functions(TYPE,NAME)
...
static TYPE *copy_##NAME(TYPE value) { return %new_copy(value, TYPE); }

when wrapping
f(uint8* source, int file_size, int* width, int* height, uint8** dest)

Fix by
==== Lib/typemaps/swigmacros.swg - my/Lib/typemaps/swigmacros.swg ====
161c161
< # define %new_copy(val,Type...) (new Type(%static_cast(val, const Type&)))
---
> # define %new_copy(val,Type...) (new Type(%static_cast(val, Type const&)))

[Olly Betts]

I've managed to piece together a complete testcase which reproduces the issue here with current git master:

$ cat test.i
%module test
%inline {
typedef unsigned char uint8;
}

%include cpointer.i
%pointer_functions(uint8*, uint8pp);

%inline {
void f(uint8* source, int file_size, int* width, int* height, uint8** dest) {}
}
$ ../preinst-swig -python -c++ test.i
$ g++ `python3-config --cflags` -fPIC -shared test_wrap.cxx -o _test.so
test_wrap.cxx: In function ‘uint8** copy_uint8pp(uint8*)’:
test_wrap.cxx:3094:24: error: invalid ‘static_cast’ from type ‘uint8*’ {aka ‘unsigned char*’} to type ‘const uint8*&’ {aka ‘const unsigned char*&’}
 3094 |     return (new uint8*(static_cast< const uint8*& >(value)));
      |                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The documentation in Library.html for %pointer_functions says: "When using this macro, type may be any type", so type being a pointer type should be supported.