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Fix DLL visibility of explicit instantiation "declaration" of internal::basic_data<void> in header format.h and the explicit instantiation "definition" in format.cc (#1134)

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* Update format.cc

As the explicit instantiation *declaration* of `internal::basic_data<void>` in format.h, this explicit instantiation *definition* should mirror FMT_API also.

* Mirror visibility of explicit instantiation declaration 

explicit instantiation declaration of internal::basic_data<void> should mirror visibility of FMT_API

* Eliminate `__declspec(dllexport)` designation on extern template internal::basic_data<> when `extern` affected during exporting phase.

* Add `FMT_EXTERN_TEMPLATE_API` for designate DLL export `extern template`

When exporting DLL, do not designate `__declspec(dllexport)` any template that has any explicit class template declaration a.k.a. `extern template`. Instead, designate `__declspec(dllexport)` at single point where we have explicit class template definition a.k.a. normal instantiation without `extern`

Note: this is a c++11 feature.

* Delete whole `FMT_USE_EXTERN_TEMPLATES` block and its condition

1. Remove whole `FMT_USE_EXTERN_TEMPLATES` block
(trailing `FMT_UDL_TEMPLATE` block)
````
#ifndef FMT_USE_EXTERN_TEMPLATES
#  ifndef FMT_HEADER_ONLY
#    define FMT_USE_EXTERN_TEMPLATES                           \
      ((FMT_CLANG_VERSION >= 209 && __cplusplus >= 201103L) || \
       (FMT_GCC_VERSION >= 303 && FMT_HAS_GXX_CXX11))
#  else
#    define FMT_USE_EXTERN_TEMPLATES 0
#  endif
#endif
````

2. Delete `FMT_USE_EXTERN_TEMPLATES` condition, only condition, that trailing basic_data class template definition.
````
#if FMT_USE_EXTERN_TEMPLATES
extern template struct basic_data<void>;
#endif
````

3. Replace `FMT_API` with new `FMT_EXTERN_TEMPLATE_API` added in `core.h` for sake of extern template of `basic_data<void>`

* Add `#define FMT_EXTERN extern` only when not `FMT_HEADER_ONLY`

* Replace `extern` on basic_data<void> with the `FMT_EXTERN` condition in core.h

* replace misspelled if !define() with ifndef
This commit is contained in:
denchat
2019-05-02 21:49:01 +07:00
committed by Victor Zverovich
parent 4a4d72f917
commit 29c10fbf6e
3 changed files with 13 additions and 15 deletions
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10
include/fmt/core.h
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@@ -189,11 +189,21 @@
# define FMT_API __declspec(dllexport)
# elif defined(FMT_SHARED)
# define FMT_API __declspec(dllimport)
# define FMT_EXTERN_TEMPLATE_API FMT_API
# endif
#endif
#ifndef FMT_API
# define FMT_API
#endif
#ifndef FMT_EXTERN_TEMPLATE_API
# define FMT_EXTERN_TEMPLATE_API
#endif
#ifndef FMT_HEADER_ONLY
# define FMT_EXTERN extern
#else
# define FMT_EXTERN
#endif
#ifndef FMT_ASSERT
# define FMT_ASSERT(condition, message) assert((condition) && message)