"src/util.hh:191:24: error: moving a local object in a return statement prevents copy elision"

[tommythorn]

I'm building and testing as many things as I can in the 2019-02-21 Fedora/RISC-V build and hit a build error in arachne-pnr. I haven't yet tried to fix it myself, but a quick look suggests it hasn't been reported before:

g++ -Isrc -std=c++11 -MD -O2 -Wall -Wshadow -Wsign-compare -Werror   -c -o src/line_parser.o src/line_parser.cc
In file included from src/bstream.hh:19,
                 from src/location.hh:19,
                 from src/chipdb.hh:19,
                 from src/chipdb.cc:16:
src/util.hh: In instantiation of ‘std::set<typename M::key_type> keys(const M&) [with M = std::map<CBit, bool>; typename M::key_type = CBit]’:
src/chipdb.cc:73:23:   required from here
src/util.hh:191:24: error: moving a local object in a return statement prevents copy elision [-Werror=pessimizing-move]
  191 |   return std::move(keys);
      |                        ^
src/util.hh:191:24: note: remove ‘std::move’ call
g++ -Isrc -std=c++11 -MD -O2 -Wall -Wshadow -Wsign-compare -Werror   -c -o src/pcf.o src/pcf.cc

g++: gcc version 9.0.1 20190219 (Red Hat 9.0.1-0.6) (GCC) arache-pnr: 840bdfdeb38809f9f6af4d89dd7b22959b176fdd build command: make -C arachne-pnr -j8

[tommythorn]

This is a temporary workaround:

make OPTDEBUGFLAGS='-MD -O2 -Wno-error=pessimizing-move'

[kpfromer]

Yeah I am also getting this error trying to install arachne-pnr via the arachne-pnr-git arch AUR package.

[JordiVM]

Same here, just tried to install arachne-pnr both through command line and arch AUR in Manjaro and had the same error on both.

[daveshah1]

Have disabled -Werror, arachne-pnr is now essentially unmaintained so this seems like a reasonable enough solution.