Re: typedef function with void parameters

William Xu <william.xwl@xxxxxxxxx> writes:

Chris Dollin <chris.dollin@xxxxxx> writes:

So, which do you want -- a function taking a `void*` or a function taking
a `char*`? They're not compatible types. Pick one.

Oh, i thought that most pointer types could be converted/stored into
void pointer.

This is true of object pointers but not function pointers.

I'm trying to wrap different function pointers into FUNC,
like,

,----
| int foo(char *p){}
| int bar(int *p){}
|
| typedef int (*FUNC)(void *);
|
| FUNC f1 = foo, f2 = bar;
`----

So, this is not allowed?

Allowed is vague. It is a constraint violation and thus requires a
diagnostic (but that could be "I will convert these function pointers
for you" or it might be "Yuck! -- compilation halted").

If you convert (with a cast) it will work on some systems but it is
not guaranteed -- your code could break with a compiler update or even
a change in optimisation level. If you are prepared to take a chance,
always make sure that the call is though a pointer whose type matches
the type of function being called.

--
Ben.
.

Relevant Pages

  • Re: Memory Structure Pointer Problems
    ... typedef struct sta { ... char* name; ... int num_cmpnds; ... A pointer to a struct cmp is almost ...
    (comp.lang.c)
  • Re: C# - getting binary data from .lib
    ... Use Marshal.AllocHGlobal to allocate the memory and pass this IntPtr to the ... int retCode = create(id, scale, ptrImage); ... You now control the pointer returned. ...
    (microsoft.public.dotnet.framework.interop)
  • Re: Passing execution to a memory address
    ... forbidden initialization of function pointer with void pointer ... int add1 ...
    (comp.lang.c)
  • Re: Another spinoza challenge
    ... You should test against the int type's limits: ... typedef struct complex ... a pointer to an integer ... A macro is preferable because it is replaced by inline code, ...
    (comp.lang.c)
  • Re: C# - getting binary data from .lib
    ... int create(int id, int scale, unsigned char *image); ... unsigned char* ptrImage = NULL; ... // Read through entire pointer byte by byte and put into managed array ...
    (microsoft.public.dotnet.framework.interop)