Bug 742755 – x11-misc/rss-glx-0.9.1-r1 fails to compile with clang

• Status: RESOLVED FIXED
• Product: Gentoo Linux

[Description Agostino Sarubbo 2020-09-16 06:41:20 UTC]

https://blogs.gentoo.org/ago/2020/07/04/gentoo-tinderbox/

Issue: x11-misc/rss-glx-0.9.1-r1 fails to compile.
Discovered on: amd64 (internal ref: tinderbox)

NOTE:
This machine uses a clang/LLVM toolchain.
If you think that this issue is strictly related to clang/LLVM please block bug 408963. If you think that this issue is strictly related to the LLD linker, please block bug 731004.
This machine uses also GLIBC-2.32. If you think that this issue is strictly related to GLIBC please block bug 736174.

[Comment 1 Agostino Sarubbo 2020-09-16 06:41:22 UTC]

Created attachment 660498 [details]
build.log

build log and emerge --info

[Comment 2 Agostino Sarubbo 2020-09-16 06:41:23 UTC]

Possible context of error(s):

flare.cpp:196:19: error: non-constant-expression cannot be narrowed from type

[Comment 3 bob5972 2021-01-17 16:12:09 UTC]

This compiles for me on GCC?

[Comment 4 Oliver Freyermuth 2021-01-20 18:16:27 UTC]

This seems to be strictly related to clang/LLVM, since clang seems to treat ""c++11-narrowing" as an error by default (unlike gcc). 
Full gcc behaviour is documented and reasoned here:
https://gcc.gnu.org/wiki/FAQ#Wnarrowing

As mentioned in that explanation, the standard does not oblige the compiler to issue an error (a "diagnostic message" is required). so neither compiler is "wrong", clang/LLVM is just more harsh here.

[Comment 5 Malcolm Lashley 2021-01-22 23:08:32 UTC]

Created attachment 684166 [details, diff]
rss-clang.patch

The attached (entirely trivial) patch fixes the Narrowing warnings for clang.
(Tested with clang-11)

Please keep this eye-candy :)

[Comment 6 Jonas Stein 2021-01-25 01:19:22 UTC]

ago, could you please test the patch on the tinderbox and report or merge?
It would be great to get the pkg patched and we should keep it in the tree. 
It seems to have several users.

[Comment 7 Larry the Git Cow 2021-02-21 16:32:22 UTC]

The bug has been closed via the following commit(s):

https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=0ea1c6d466de8412a60fc576c6f3140104367323

commit 0ea1c6d466de8412a60fc576c6f3140104367323
Author:     Alexander Miller <[e-mail]>
AuthorDate: 2021-02-21 16:31:54 +0000
Commit:     David Seifert <[e-mail]>
CommitDate: 2021-02-21 16:31:54 +0000

    x11-misc/rss-glx: Fix C++11 narrowing issues
    
    This fixes building with clang. Thanks to Malcolm Lashley
    for the patch.
    
    Closes: https://bugs.gentoo.org/742755
    Signed-off-by: Alexander Miller <[e-mail]>
    Package-Manager: Portage-3.0.13, Repoman-3.0.2
    Signed-off-by: David Seifert <[e-mail]>

 .../files/rss-glx-0.9.1-c++11-narrowing.patch      |  22 ++++
 x11-misc/rss-glx/rss-glx-0.9.1-r2.ebuild           | 129 +++++++++++++++++++++
 2 files changed, 151 insertions(+)