Re: error with d28016d16e9a (change to jsonencode.cc)

On 10/01/2020 08:26 AM, Benjamin Abbott wrote:
> Rik
>
> I’m seeing a build problem on the default branch when building on macOS (10.15.6) using Homebrew for dependencies and Apple’s clang version 12.0.0 (clang-1200.0.32.2).
>
> If I revert the change below, I’m able to build.
>
> http://hg.savannah.gnu.org/hgweb/octave/rev/d28016d16e9a
>
> libtool: compile:  g++ -std=gnu++11 -DHAVE_CONFIG_H -I. -Iliboctave -I./liboctave -I./liboctave/array -Iliboctave/numeric -I./liboctave/numeric -Iliboctave/operators -I./liboctave/operators -I./liboctave/system -I./liboctave/util -I./libinterp/octave-value -Ilibinterp -I./libinterp -I./libinterp/operators -Ilibinterp/parse-tree -I./libinterp/parse-tree -Ilibinterp/corefcn -I./libinterp/corefcn -I./liboctave/wrappers -I/usr/local/opt/hdf5/include -I/usr/local/Cellar/graphicsmagick/1.3.35/include/GraphicsMagick -I/usr/local/Cellar/fftw/3.3.8_2/include -I/usr/local/Cellar/fftw/3.3.8_2/include -I/usr/local/Cellar/fontconfig/2.13.1/include -I/usr/local/opt/freetype/include/freetype2 -I/usr/local/opt/freetype/include/freetype2 -I/usr/local/opt/hdf5/include -I/usr/local/opt/readline/include -I/usr/local/opt/sqlite/include -I/usr/local/opt/openssl/include -I/usr/local/opt/gettext/include -I/usr/local/opt/icu4c/include -I/usr/local/opt/qt5/include -I/usr/local/opt/sundials27/include -I/usr/local/opt/zlib/include -fPIC -D_THREAD_SAFE -pthread -Wall -W -Wshadow -Woverloaded-virtual -Wold-style-cast -Wformat -Wpointer-arith -Wwrite-strings -Wcast-align -Wcast-qual -g -O2 -MT libinterp/corefcn/libcorefcn_la-jsonencode.lo -MD -MP -MF libinterp/corefcn/.deps/libcorefcn_la-jsonencode.Tpo -c libinterp/corefcn/jsonencode.cc  -fno-common -DPIC -o libinterp/corefcn/.libs/libcorefcn_la-jsonencode.o
> libinterp/corefcn/jsonencode.cc:414:20: error: 'auto' not allowed in lambda parameter
>         ([] (const auto& old_warning_state)
>                    ^~~~
> libinterp/corefcn/jsonencode.cc:414:26: warning: unused parameter 'old_warning_state' [-Wunused-parameter]
>         ([] (const auto& old_warning_state)
>                          ^
> libinterp/corefcn/jsonencode.cc:425:20: error: 'auto' not allowed in lambda parameter
>         ([] (const auto& old_warning_state)
>                    ^~~~
> libinterp/corefcn/jsonencode.cc:425:26: warning: unused parameter 'old_warning_state' [-Wunused-parameter]
>         ([] (const auto& old_warning_state)
>                          ^
> In file included from libinterp/corefcn/jsonencode.cc:32:
> In file included from libinterp/corefcn/error.h:35:
> ./liboctave/util/unwind-prot.h:171:9: error: no matching constructor for initialization of 'std::function<void ()>'
>       : m_fcn (std::bind (fcn, args...))
>         ^      ~~~~~~~~~~~~~~~~~~~~~~~~
>
> Ben

In one sense, this is easy to resolve.  Instead of using the keyword "auto"
just specify the exact type of the underlying variable.  However, the
compiler really should be able to handle this construct.  Could you try
'g++ --version'?  And is it really GNU g++ or is this a soft link to clang?

--Rik