Am Fri, 14 Mar 2014 10:53:59 -0700
schrieb Walter Bright <newshou...@digitalmars.com>:
> On 3/14/2014 10:26 AM, Johannes Pfau wrote:
> > I use manifest constants instead of version identifiers as well. If
> > a version identifier affects the public API/ABI of a library, then
> > the library and all code using the library always have to be
> > compiled with the same version switches(inlining and templates make
> > this an even bigger problem). This is not only inconvenient, it's
> > also easy to think of examples where the problem will only show up
> > as crashes at runtime. The only reason why that's not an issue in
> > phobos/druntime is that we only use compiler defined versions
> > there, but user defined versions are almost unusable.
>
> Use this method:
>
>
> --------
> import wackyfunctionality;
> ...
> WackyFunction();
> --------
> module wackyfunctionality;
>
> void WackyFunction() {
> version (Linux)
> SomeWackyFunction();
> else version (OSX)
> SomeWackyFunction();
> else
> ... workaround ...
> }
> --------
I meant really 'custom versions', not OS-related. For example cairoD
wraps the cairo C library. cairo can be compiled without or with PNG
support. Historically cairoD used version(CAIRO_HAS_PNG_SUPPORT) for
this.
Then in cairo.d
version(CAIRO_HAS_PNG_SUPPORT)
{
extern(C) int cairo_save_png(char* x);
void savePNG(string x){cairo_save_png(toStringz(x))};
}
now I have to use version=CAIRO_HAS_PNG_SUPPORT when compiling cairoD,
but every user of cairoD also has to use version=CAIRO_HAS_PNG_SUPPORT
or the compiler will hide the savePNG functions. There are also
examples where not using the same version= switches causes runtime
crashes.
Compiler defined version(linux, OSX) are explicitly not affected by
this issue as they are always defined by the compiler for all modules.
