22 Apr
2017
22 Apr
'17
1:39 a.m.
On 04/21/2017 03:42 PM, Sylvain Munaut wrote:
I see your point and agree that QMake's behavior is undesirable. I also
agree that removing includedir will break compiling with --prefix
without --sysroot; from a quick survey of a bunch of .pc files, they all
include either -I${includedir} or -I${includedir}/project. The second
category will not hit these issues while the first will.
Bugs have been filed on QMake regarding this in the past:
https://bugreports.qt.io/browse/QTBUG-53375
https://bugreports.qt.io/browse/QTBUG-53367
A patch was even drafted to fix it:
https://codereview.qt-project.org/#/c/159215
The patch was abandoned with this reasoning:
"The idea is that -isystem also suppresses warnings from files found in
those paths. We'd like to keep that functionality.
The problem is that -isystem /usr/include, specifically, reorders that
path."
The workaround in qtBittorrent was to explicitly remove the include/libs
that QMake had added:
https://github.com/qbittorrent/qBittorrent/commit/d9d49b6d0bb71ccc086968f26…
Certainly not ideal, but it may be the only solution.
This could work, but it still would break some machine that uses
somewhere else for system compiler path. Perhaps doing what qtbittorrent
did and just removing what QMake adds is the best solution, absent QMake
fixing it.
In both cases,
the maintainers state that the right solution is to not do -I
/usr/include. AFAICT, this means there are two options:
Not really no ...
They say to not use the -isystem /usr/include
My opinion there is that qmake is broken doing the translation from
-Ixxx to -isystem xxx blindly when both don't have _exactly_ the same
semantic. QMake should check the system include list when doing the
translation and omit the system ones to compensate for the difference
of behavior of -I vs -isystem.
(a) Don't export -I /usr/include in the .pc
file.
(b) Manually remove -I /usr/include for anyone who compiles with GCC 6 and
needs to use rtl-sdr.
Solution (a) seems cleaner to me. If you have another way that avoids
breaking packages that include rtl-sdr and use GCC 6, I'm happy to hear it.
Well (a) is fine ... but you can only remove /usr/include ... not ${includedir}
So you need to test is includedir is indeed /usr/include and then you
can omit it but if not, then you need to leave it.