Fix compilation with -fno-common (new GCC 10 default)#818
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natoscott merged 2 commits intoperformancecopilot:masterfrom Jan 13, 2020
Merged
Fix compilation with -fno-common (new GCC 10 default)#818natoscott merged 2 commits intoperformancecopilot:masterfrom
natoscott merged 2 commits intoperformancecopilot:masterfrom
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SDS_NOINIT is currently declared in sds.h without extern, resulting in multiple definitions across sds.h consumers. With GCC 10, the default of -fcommon option will change to -fno-common, resulting in an error: Signed-off-by: David Disseldorp <ddiss@suse.de>
The global_version_major and global_version_minor variables are declared in pmdacifs.h. Currently both cifs/pmda.c and cifs/stats.c carry definitions, resulting in an error when compiling with -fno-common (a new GCC 10 default). Signed-off-by: David Disseldorp <ddiss@suse.de>
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FWIW, I've also submitted the sds fix upstream via antirez/sds#120 , but given the backlog of PRs and lack of activity, I doubt it'll be merged there any time soon. |
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As described in https://bugzilla.opensuse.org/show_bug.cgi?id=1160244
Starting from the upcoming GCC release 10, the default of -fcommon option will change to -fno-common:
In C, global variables with multiple tentative definitions will result in linker errors. Global variable accesses are also more efficient on various targets.
Porting advice:
A common mistake in C is omitting
externwhen declaring a global variable in a header file. If the header is included by several files itresults 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
externin 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.Recommendations for package maintainers: