read/write function_ptrs as just void*, and not as 'array of bytes'

read/write function_ptrs as just void*, and not as 'array of bytes'

BUG=skia:

Committed: http://code.google.com/p/skia/source/detail?r=14224

[mtklein, 2014-04-16 15:58:21]

lgtm

[reed1, 2014-04-16 15:59:36]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-04-16 15:59:52]

CQ is trying da patch. Follow status at
https://skia-tree-status.appspot.com/cq/reed@google.com/240013005/1

[commit-bot: I haz the power, 2014-04-16 16:24:11]

Change committed as 14224

[bungeman-skia, 2014-04-16 16:51:36]

https://codereview.chromium.org/240013005/diff/1/include/core/SkReadBuffer.h
File include/core/SkReadBuffer.h (right):

https://codereview.chromium.org/240013005/diff/1/include/core/SkReadBuffer.h#...
include/core/SkReadBuffer.h:76: void* readFunctionPtr() { return
fReader.readPtr(); }
So, I think this was 'incorrect' before, so this change makes no real
difference. However, it is technically undefined to cast a function pointer to a
void pointer. POSIX defines the way we do things in the call to dlsym in
SkFontHost_FreeType.cpp (because dlsym is defined to return a void*). Windows is
actually better here, as GetProcAddress returns FARPROC which is actually a
function pointer.

The spec does state that you can cast a function pointer to another one, so long
as it is cast back to the original before making a call through it. I would
propose a 'typedef void (*SkVoidProc)()' which would be what this and the
associated writer would deal in.

[mtklein, 2014-04-16 16:55:05]

On 2014/04/16 16:51:36, bungeman1 wrote:
> https://codereview.chromium.org/240013005/diff/1/include/core/SkReadBuffer.h
> File include/core/SkReadBuffer.h (right):
> 
>
https://codereview.chromium.org/240013005/diff/1/include/core/SkReadBuffer.h#...
> include/core/SkReadBuffer.h:76: void* readFunctionPtr() { return
> fReader.readPtr(); }
> So, I think this was 'incorrect' before, so this change makes no real
> difference. However, it is technically undefined to cast a function pointer to
a
> void pointer. POSIX defines the way we do things in the call to dlsym in
> SkFontHost_FreeType.cpp (because dlsym is defined to return a void*). Windows
is
> actually better here, as GetProcAddress returns FARPROC which is actually a
> function pointer.
> 
> The spec does state that you can cast a function pointer to another one, so
long
> as it is cast back to the original before making a call through it. I would
> propose a 'typedef void (*SkVoidProc)()' which would be what this and the
> associated writer would deal in.

Is there a way for us to write a generic "accepts any function pointer" and
we'll do the cast for the caller in writer?  The reader's going to have to do a
cast anyway, but it'd be sad to force all the calls to writer to make an extra
cast to SkVoidProc themselves.

I'm happy, very happy even, to make it inconvenient to do dumb things like pass
in a non-function pointer here.