Re: Wget2 cross-compile on iOS arm64

[Jeffrey Walton]

On Tue, Mar 23, 2021 at 6:16 AM Ryan Schmidt <wget@ryandesign.com> wrote:
>
>
>
> On Mar 23, 2021, at 04:01, Jeffrey Walton wrote:
>
> > On Tue, Mar 23, 2021 at 12:38 AM Ryan Schmidt wrote:
> >>
> >> On Mar 22, 2021, at 17:56, Jeffrey Walton wrote:
> >>
> >>> It looks like  this is an Autotools problem. Autotools should test if
> >>> ccp works as expected, and avoid cpp if it does not. Autotools should
> >>> not break the build.
> >>>
> >>> Perl works around Apple's cpp:
> >>> https://github.com/Perl/perl5/blob/blead/hints/darwin.sh#L131.
> >>
> >> You're referring to the part of their code that adds -no-cpp-precomp if 
> >> the compiler accepts it? The last version of Apple gcc that did anything 
> >> in response to -no-cpp-precomp was Apple gcc 3.1. Apple gcc 3.3 and later 
> >> do nothing in response to -no-cpp-precomp. That flag is ancient history.
> >>
> > Actually I was talking about the comment that says, " Avoid Apple's
> > cpp precompiler".
>
>
> .....this is the block of code including that comment:
>
>
>
> # Avoid Apple's cpp precompiler, better for extensions
> if [ "X`echo | ${cc} -no-cpp-precomp -E - 2>&1 >/dev/null`" = "X" ]; then
>     cppflags="${cppflags} -no-cpp-precomp"
>
>     # This is necessary because perl's build system doesn't
>     # apply cppflags to cc compile lines as it should.
>     ccflags="${ccflags} ${cppflags}"
> fi
>
>
>
> So they wish to avoid Apple's cpp precompiler ("cpp-precomp"), and the way 
> that they do that is that they test whether the compiler supports the flag 
> "-no-cpp-precomp" and if so they add that flag which instructs Apple gcc to 
> use gcc's standard preprocessor instead.
>
> cpp-precomp existed in Apple gcc 3.1 and earlier. Apple removed it in Apple 
> gcc 3.3 and later. In Apple gcc 3.3 and later the flag "-no-cpp-precomp", 
> while still accepted, is ignored and does nothing. gcc's standard 
> preprocessor is used in all cases in Apple gcc 3.3 and later. See the release 
> notes:
>
> https://opensource.apple.com/source/gccfast/gccfast-1626/AppleReleaseNotes.html?f=text
>
> Apple gcc as a whole has been dead for a decade already. We use clang now.
>
> So again, what you're talking about is ancient history and is not the cause 
> of the build failure you saw. I believe the cause of the build failure you 
> saw is that you weren't providing the right flags to accomplish 
> cross-compilation. I showed a set of flags that worked for me and I suggest 
> you work from there.

Perl does not perform any tests with cpp. That's consistent with the comment.

Jeff