Well sure, because you need one, and only one, file that actually
defines it.
Previously every file that included the header created a definition
which meant you could wind up with multiple definitions if more than
one file included it.
Now no file that includes the header will create a definition unless
the file contains a definition of the variable (ie without extern) so
if there isn't such a file already then you will need to choose an
appropriate file and add the definition to it.
Tom
On 23/01/2020 15:48, Robert-André Mauchin wrote:
On Tuesday, 21 January 2020 13:35:03 CET Miro Hrončok wrote:
Hello,
we try to rebuild all Python packages against Python 3.9 and report the
failures. I've seen several similar failures in a row now that can be
reproduced
in Fedora rawhide with the new gcc version.
ld errors on multiple definitions of ..., for example:
ld:
tests/bp_account.o:/builddir/build/BUILD/kernel-5.4.fc32/linux-5.4/tools/per
f/tests/bp_account.c:22:
multiple definition of `the_var';
tests/bp_signal.o:/builddir/build/BUILD/kernel-5.4.fc32/linux-5.4/tools/perf
/tests/bp_signal.c:38:
first defined here
This is a known thing in gcc 10:
https://gcc.gnu.org/gcc-10/porting_to.html#common
"Default to -fno-common
A common mistake in C is omitting extern when declaring a global variable in
a
header file. If the header is included by several files it results in
multiple definitions of the same variable. In previous GCC versions this
error is ignored. GCC 10 defaults to -fno-common, which means a linker
error will now be reported. To fix this, use extern in header files when
declaring global variables, and ensure each global is defined in exactly
one C file. As a workaround, legacy C code can be compiled with -fcommon.
int x; // tentative definition - avoid in header files
extern int y; // correct declaration in a header file"
Here are some packages affected:
nemo-extensions
https://bugzilla.redhat.com/show_bug.cgi?id=1793470
thunarx-python
https://src.fedoraproject.org/rpms/thunarx-python/pull-request/1
kernel-tools
https://bugzilla.redhat.com/show_bug.cgi?id=1793473
https://bugzilla.redhat.com/show_bug.cgi?id=1793424
gnome-abrt, glusterfs...
Before I go and file dozens of bugzillas, do we want to handle this somehow
better?
--
Miro Hrončok
--
Phone: +420777974800
IRC: mhroncok
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How to fix the affected packages? For some I ised extern and it worked but for
other using extern resulted in error like:
/usr/bin/ld: /builddir/build/BUILD/uTox-0.17.1/src/xlib/main.c:590: undefined
reference to `font_small_lineheight'
Lots of undefined reference despite the var being marked as global. All the
packages I have to fix have deadish upstream.
Any help appreciated.
Best regards,
Robert-André
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--
Tom Hughes (tom@xxxxxxxxxx)
http://compton.nu/
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