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Fix -Wignored-reference-qualifiers #3677

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georgthegreat
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In certain STLs, std::vector<bool>::reference is just bool&.
Prepending const causes the following warning:

include/nlohmann/detail/conversions/to_json.hpp:271:42: error: 'const' qualifier on reference type 'std::vector<bool>::reference' (aka 'bool &') has no effect [-Werror,-Wignored-reference-qualifiers]

This PR fixes the problem.

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  • The C++11 support varies between different compilers and versions. Please note the list of supported compilers. Some compilers like GCC 4.7 (and earlier), Clang 3.3 (and earlier), or Microsoft Visual Studio 13.0 and earlier are known not to work due to missing or incomplete C++11 support. Please refrain from proposing changes that work around these compiler's limitations with #ifdefs or other means.
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In certain STLs, `std::vector<bool>::reference` is just `bool&`.
Prepending `const` causes the following warning:
```
include/nlohmann/detail/conversions/to_json.hpp:271:42: error: 'const' qualifier on reference type 'std::vector<bool>::reference' (aka 'bool &') has no effect [-Werror,-Wignored-reference-qualifiers]
```

This PR fixes the problem.
@falbrechtskirchinger
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Which STL would that be? ( So we can test.)

@georgthegreat
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We use custom STL with std::vector compation disabled.
This is the vector we use.

@falbrechtskirchinger
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I see.

I did fix it slightly differently (#3678). We can simply disable the to_json function in that case as we already have one for bool.
That should work for you, right?

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3 participants