macOS 11.7.10: ISO C++17 error under Big Sur

[steamfan]

Hello,
I donwloaded conky sources from GitHub and followed the instructions under MacOS Build.
At the last stepcmake --build .I get these error messages:

[ 17%] Building CXX object src/CMakeFiles/conky.dir/colours.cc.o
In file included from /System/Volumes/Data/NAS/Applications/conky/conky/src/colours.cc:45:
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:63:20: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
gperf_case_strcmp (register const char *s1, register const char *s2)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:63:45: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
gperf_case_strcmp (register const char *s1, register const char *s2)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:85:24: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
color_name_hash::hash (register const char *str, register unsigned int len)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:85:50: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
color_name_hash::hash (register const char *str, register unsigned int len)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:103:3: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register unsigned int hval = len;
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:149:31: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
color_name_hash::in_word_set (register const char *str, register unsigned int len)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:149:57: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
color_name_hash::in_word_set (register const char *str, register unsigned int len)
^~~~~~~~~
/System/Volumes/Data/NAS/Applications/conky/conky/build/colour-names.cc:1556:11: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
register const char *s = wordlist[key].name;

How can I solve those errors?

[brndnmtthws]

Try installing gperf from homebrew with brew install gperf, then recompile Conky, and you should be good to go.

It looks like you hit an issue with older versions of gperf: https://savannah.gnu.org/bugs/?53028.

Most likely it's because macOS include gperf, and your version is unpatched. It's fixed in gperf 3.1 (https://git.savannah.gnu.org/gitweb/?p=gperf.git;a=commit;h=baf89d87f0d94b83e7764569da9d84dd36f82ba9), which is available from Homebrew: https://formulae.brew.sh/formula/gperf.

We can perhaps disable the warning when building that particular file, however, to make it compile with older versions.

[brndnmtthws]

I updated the Wiki to include gperf in the dependency list.

[steamfan]

Thanks for your support. This solved the issue.