Fix "-Wundef" warning when building as C++20 #85
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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>
martinmoene
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May 7, 2024
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When including
span.hppin a source file compiled as C++20, I get an error similar to this:Fix it by checking if
span_HAVE_STRUCT_BINDINGis defined. Unfortunately, I couldn't find a way to makedefined()work withspan_HAVE( STRUCT_BINDING ).An alternative would be to move the definition of
span_HAVE_STRUCT_BINDINGoutside of thespan_USES_STD_SPANifdef.Fixes #84.