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-Wundef when building with g++ -std=c++20 #84

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simark opened this issue Apr 29, 2024 · 0 comments
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-Wundef when building with g++ -std=c++20 #84

simark opened this issue Apr 29, 2024 · 0 comments

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@simark
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simark commented Apr 29, 2024 •
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Using master as of today, I get:

$ g++ -x c++-header span.hpp -Wundef -Werror -std=c++20 
span.hpp:43:33: error: "span_HAVE_STRUCT_BINDING" is not defined, evaluates to 0 [-Werror=undef]
   43 | #define span_HAVE( feature )  ( span_HAVE_##feature )
      |                                 ^~~~~~~~~~
span.hpp:1873:5: note: in expansion of macro ‘span_HAVE’
 1873 | #if span_HAVE( STRUCT_BINDING )
      |     ^~~~~~~~~
cc1plus: all warnings being treated as errors
simark added a commit to simark/span-lite that referenced this issue May 6, 2024
@simark
Fix "-Wundef" warning when building as C++20
e64ea09 
When including `span.hpp` in a source file compiled as C++20, I get an
error similar to this:

    $ g++ -x c++-header span.hpp -Wundef -Werror -std=c++20
    span.hpp:43:33: error: "span_HAVE_STRUCT_BINDING" is not defined, evaluates to 0 [-Werror=undef]
       43 | #define span_HAVE( feature )  ( span_HAVE_##feature )
          |                                 ^~~~~~~~~~
    span.hpp:1873:5: note: in expansion of macro ‘span_HAVE’
     1873 | #if span_HAVE( STRUCT_BINDING )
          |     ^~~~~~~~~

Fix it by checking if `span_HAVE_STRUCT_BINDING` is defined.  This
Unfortunately, I couldn't find a way to make `defined()` work with
`span_HAVE( STRUCT_BINDING )`.

An alternative would be to move the definition of
`span_HAVE_STRUCT_BINDING` outside of the `span_USES_STD_SPAN` ifdef.

Fixes martinmoene#84.

Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
@simark simark mentioned this issue May 6, 2024
Closed
simark added a commit to simark/span-lite that referenced this issue May 6, 2024
@simark
Fix "-Wundef" warning when building as C++20
6a5024b 
When including `span.hpp` in a source file compiled as C++20, I get an
error similar to this:

    $ g++ -x c++-header span.hpp -Wundef -Werror -std=c++20
    span.hpp:43:33: error: "span_HAVE_STRUCT_BINDING" is not defined, evaluates to 0 [-Werror=undef]
       43 | #define span_HAVE( feature )  ( span_HAVE_##feature )
          |                                 ^~~~~~~~~~
    span.hpp:1873:5: note: in expansion of macro ‘span_HAVE’
     1873 | #if span_HAVE( STRUCT_BINDING )
          |     ^~~~~~~~~

Fix it by checking if `span_HAVE_STRUCT_BINDING` is defined.
Unfortunately, I couldn't find a way to make `defined()` work with
`span_HAVE( STRUCT_BINDING )`.

An alternative would be to move the definition of
`span_HAVE_STRUCT_BINDING` outside of the `span_USES_STD_SPAN` ifdef.

Fixes martinmoene#84.

Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
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Fix "-Wundef" warning when building as C++20 simark/span-lite
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@simark