Re: [PATCH 3/4] scripts: unify libusb.h inclusion

From: Ahmad Fatoum <a.fatoum@pengutronix.de>
To: Trent Piepho <trent.piepho@igorinstitute.com>
Cc: Barebox List <barebox@lists.infradead.org>,
	ejo@pengutronix.de, rhi@pengutronix.de, uol@pengutronix.de,
	renaud.barbier@abaco.com
Subject: Re: [PATCH 3/4] scripts: unify libusb.h inclusion
Date: Wed, 15 Sep 2021 10:55:58 +0200	[thread overview]
Message-ID: <fda4d46a-1025-4bde-4ee0-bebbe20932ab@pengutronix.de> (raw)
In-Reply-To: <CAMHeXxMyGYAM=TSE=V9h8jnkO8rmDE-e5axKeCwURvqcYoG63A@mail.gmail.com>

On 14.09.21 21:22, Trent Piepho wrote:
> On Tue, Sep 14, 2021 at 6:21 AM Ahmad Fatoum <a.fatoum@pengutronix.de> wrote:
>>
>> I've also run into downstream patches around broken toolchains that
>> change <libusb.h> to <libusb-1.0/libusb.h>, so the header is found.
> 
> How does this become a problem exactly?  If the toolchain has the file
> in the location <includedir>/ibusb-1.0/libusb.h, then shouldn't
> pkg-config --cflags have returned -I<includedir>/libusb-1.0 and it
> would then find the file just fine?
>
> Or is the problem really that the cross building setup does not have
> correct .pc files?

I ran twice into downstream patches patching imx-usb-loader. So apparently

-lusb1.0 was returned but the CFLAGS were correctl set.

> If it's the latter, then I'll point out that my previous email would
> let someone put CROSS_LIBUSB_CFLAGS=-I<cross-include-dir>/libusb-1.0
> on the make command line and get a build without having .pc files.
> This is pretty much what you get with autoconf configure scripts when
> you put headers in a non-standard place and don't have .pc files setup
> to find them.  You need to supply CFLAGS, LDFLAGS, etc. variables with
> the proper -L and -I options to find them.

I wrote this patch initially to support a pkg-config less build:
If CROSS_PKG_CONFIG wasn't set (no default), we would just use -lusb-1.0
and hope it works. For the header __has_include would try the two paths
that most probably would work.

Now that I dropped that fallback, I should probably drop this patch
as well and let people with broken pkg-config files just fix their
brokenness.

>> +++ b/scripts/libusb.h
> 
> By naming this libusb.h, it requires that "libusb.h" find this file
> and <libusb.h> find a different header of the same name.  That's
> certainly possible by being careful with the "" and <> search paths.
> But it seems unnecessarily fragile.  I suggest using libusb-wrapper.h
> for this file so you avoid name collisions with the real header file.

That's a good point. I'll drop this patch though for v2.

Thanks for your feedback,
Ahmad

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