Re: [patch][c++] fix "invalid conversion from ‘void*’ to ‘char*’"

[Lorenzo Donati <lorenzodonatibz@...>]

On 27/06/2016 15:12, Roberto Ierusalimschy wrote:
> > It was thus said that the Great Irfan Adilovic once stated:
> > > In the 5.3.3 release, lua/lstrlib.cc:936:
> > >
> > >      char *ppoint = memchr(buff, point, nb);
> > >
> > > is not valid c++ code. This should be fixed with a c-style cast:
> >
> >    But it *is* valid C code.  In C, it's recommended *not* to cast the result
> > of malloc() as it can hide errors (mainly missing declarations---in C,
> > without a prototype, the compiler will assume a function returns an int).
>
> We always use -Wmissing-prototypes, so this does not seem to be an
> issue. Note that Lua already casts all the result of malloc (see macros
> in 'lmem.h')---otherwise there would be lots of errors like this one.

Wouldn't it be useful to use some macro magic to remove the cast when 
the code is built as plain C, so that the code the compiler sees is 
conforming both as C and as C++?

For example define a function-like macro like

MALLOC_CAST(typename, expr)

that expands to nothing when compiled as C?

> -- Roberto

Cheers!

-- Lorenzo