Build fails from AUR "wlroots-git"

[joachimneu]

When trying to install "wlroots-git" from AUR, the build fails with:

Build targets in project: 116

wlroots 0.10.0

        systemd: 1
        elogind: 0
       xwayland: 1
    x11_backend: 1
      xcb-icccm: 1
     xcb-errors: 1

Found ninja-1.10.0 at /usr/bin/ninja
ninja: Entering directory `build'
[296/326] Compiling C object 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o'
FAILED: examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o 
cc -Iexamples/c590b3c@@screencopy-dmabuf@exe -Iexamples -I../examples -Iprotocol -I/usr/lib/libffi-3.2.1/include -I/usr/include/libpng16 -I/usr/include/libdrm -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Werror -std=c11 -g -DWLR_USE_UNSTABLE -Wundef -Wlogical-op -Wmissing-include-dirs -Wold-style-definition -Wpointer-arith -Winit-self -Wstrict-prototypes -Wimplicit-fallthrough=2 -Wendif-labels -Wstrict-aliasing=2 -Woverflow -Wmissing-prototypes -Wno-missing-braces -Wno-missing-field-initializers -Wno-unused-parameter -fmacro-prefix-map=../= -DLIBINPUT_MAJOR=1 -DLIBINPUT_MINOR=15 -DLIBINPUT_PATCH=4 '-DICONDIR="/usr/share/icons"' -march=x86-64 -mtune=generic -O2 -fno-plt -g -fvar-tracking-assignments -fdebug-prefix-map=/home/joachim/.cache/yay/wlroots-git/src=/usr/src/debug -D_FORTIFY_SOURCE=2 -MD -MQ 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o' -MF 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o.d' -o 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o' -c ../examples/screencopy-dmabuf.c
In file included from /usr/include/string.h:495,
                 from ../examples/screencopy-dmabuf.c:33:
In function ‘strncpy’,
    inlined from ‘find_render_node’ at ../examples/screencopy-dmabuf.c:90:3,
    inlined from ‘main’ at ../examples/screencopy-dmabuf.c:291:7:
/usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 256 equals destination size [-Werror=stringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
[304/326] Generating symbol file 'wlroots@sha/libwlroots.so.5.symbols'
ninja: build stopped: subcommand failed.
==> ERROR: A failure occurred in build().
    Aborting...
Error making: wlroots-git

[jtheoof]

Hi @emersion @any1 it looks like commit: e0d4f7517: examples: Add screencopy-dmabuf example is now causing compiling errors on Arch systems.

ninja: Entering directory `build'
[20/21] Compiling C object 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o'
FAILED: examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o
ccache cc -Iexamples/c590b3c@@screencopy-dmabuf@exe -Iexamples -I../examples -Iprotocol -I/usr/include/libpng16 -I/usr/include/libdrm -fdiagnostics-color=always -pipe -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -Werror -std=c11 -g -DWLR_USE_UNSTABLE -Wundef -Wlogical-op -Wmissing-include-dirs -Wold-style-definition -Wpointer-arith -Winit-self -Wstrict-prototypes -Wimplicit-fallthrough=2 -Wendif-labels -Wstrict-aliasing=2 -Woverflow -Wmissing-prototypes -Wno-missing-braces -Wno-missing-field-initializers -Wno-unused-parameter -fmacro-prefix-map=../= -DLIBINPUT_MAJOR=1 -DLIBINPUT_MINOR=15 -DLIBINPUT_PATCH=5 '-DICONDIR="/usr/share/icons"' -march=x86-64 -mtune=generic -O2 -fno-plt -g -fvar-tracking-assignments -fdebug-prefix-map=/home/jattali/.cache/yay/wlroots-git/src=/usr/src/debug -D_FORTIFY_SOURCE=2 -MD -MQ 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o' -MF 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o.d' -o 'examples/c590b3c@@screencopy-dmabuf@exe/screencopy-dmabuf.c.o' -c ../examples/screencopy-dmabuf.c
In file included from /usr/include/string.h:495,
                 from ../examples/screencopy-dmabuf.c:33:
In function ‘strncpy’,
    inlined from ‘find_render_node’ at ../examples/screencopy-dmabuf.c:90:3,
    inlined from ‘main’ at ../examples/screencopy-dmabuf.c:291:7:
/usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 256 equals destination size [-Werror=stringop-truncation]
  106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
ninja: build stopped: subcommand failed.

However it's only happening when building straight for AUR. If I try the same build parameters as the PKGBUILD suggests, I cannot reproduce this issue. I am a bit puzzled.

See #2133

[emersion]

Does this patch fix the issue?

diff --git a/examples/screencopy-dmabuf.c b/examples/screencopy-dmabuf.c
index ea6b9f50a73f..ebc6ea759bae 100644
--- a/examples/screencopy-dmabuf.c
+++ b/examples/screencopy-dmabuf.c
@@ -87,7 +87,7 @@ static bool find_render_node(char *node, size_t maxlen) {
                        continue;
                }
 
-               strncpy(node, dev->nodes[DRM_NODE_RENDER], maxlen);
+               strncpy(node, dev->nodes[DRM_NODE_RENDER], maxlen - 1);
                node[maxlen - 1] = '\0';
                r = true;
                break;

[any1]

Yeah, that warning is rather annoying, and quite pointless in this case. Would people be opposed to adding strlcpy to the project?
cc @ddevault

[emersion]

We can't use strlcpy because it's non-standard.

[any1]

Many projects include an implementation of strlcpy for compatibility.

[ddevault]

Meh. Looks like gcc covers our ass anyway.

[jtheoof]

@emersion your patch fixes the issue. Thanks.

[joachimneu]

Great, thanks! :)