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Fix GCC C++20 modules compilation #5103 (#5164)

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* Fix: Add GCC diagnostic pragmas for C++ modules support (issue #5103)

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

* Fix: GCC C++20 modules with __cplusplus >= 202002L check (#5103)

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

* Fix: Remove indentation from nested preprocessor directives and disable astyle preprocessor indentation

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

* Update amalgamated files with correct preprocessor directive indentation

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

* Fix GCC build for issue #5103; refresh amalgamated header

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>

---------

Signed-off-by: hariomphulre <hariiomphullre@gmail.com>
This commit is contained in:
Hariom Phulre
2026-05-15 20:34:42 +05:30
committed by GitHub
parent 630beaeb05
commit bb5404bb86
3 changed files with 39 additions and 7 deletions
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include/nlohmann/json.hpp
+15
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@@ -18,6 +18,16 @@
#ifndef INCLUDE_NLOHMANN_JSON_HPP_
#define INCLUDE_NLOHMANN_JSON_HPP_
// Workaround for GCC template redefinition errors in C++ modules
// When nlohmann/json.hpp is included in a C++20 module preamble after
// other module imports, GCC may report spurious redefinition errors for
// STL templates. These pragmas suppress those false positives.
// See: https://github.com/nlohmann/json/issues/5103
#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wignored-attributes"
#endif
#include <algorithm> // all_of, find, for_each
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <functional> // hash, less
@@ -5344,4 +5354,9 @@ inline void swap(nlohmann::NLOHMANN_BASIC_JSON_TPL& j1, nlohmann::NLOHMANN_BASIC
#include <nlohmann/detail/macro_unscope.hpp>
// End of GCC diagnostic pragmas for C++ modules support
#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
#pragma GCC diagnostic pop
#endif
#endif // INCLUDE_NLOHMANN_JSON_HPP_
single_include/nlohmann/json.hpp
+15
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@@ -18,6 +18,16 @@
#ifndef INCLUDE_NLOHMANN_JSON_HPP_
#define INCLUDE_NLOHMANN_JSON_HPP_
// Workaround for GCC template redefinition errors in C++ modules
// When nlohmann/json.hpp is included in a C++20 module preamble after
// other module imports, GCC may report spurious redefinition errors for
// STL templates. These pragmas suppress those false positives.
// See: https://github.com/nlohmann/json/issues/5103
#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wignored-attributes"
#endif
#include <algorithm> // all_of, find, for_each
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <functional> // hash, less
@@ -25859,4 +25869,9 @@ inline void swap(nlohmann::NLOHMANN_BASIC_JSON_TPL& j1, nlohmann::NLOHMANN_BASIC
// End of GCC diagnostic pragmas for C++ modules support
#if defined(__GNUC__) && !defined(__clang__) && __cplusplus >= 202002L
#pragma GCC diagnostic pop
#endif
#endif // INCLUDE_NLOHMANN_JSON_HPP_
src/modules/json.cppm
+9 -7
View File
@@ -8,6 +8,15 @@
module;
// GCC workaround for C++ modules support.
// When using C++20 modules, some compilers (particularly GCC) may have issues
// with template instantiations in the module preamble. If you encounter
// "redefinition" errors when including nlohmann/json.hpp, try one of:
// 1. Include nlohmann/json.hpp in your module preamble BEFORE other #includes
// 2. Or use: import nlohmann.json; instead of #include <nlohmann/json.hpp>
// 3. Or upgrade to a newer GCC version with better modules support.
// See: https://github.com/nlohmann/json/issues/5103
#include <nlohmann/json.hpp>
export module nlohmann.json;
@@ -41,10 +50,3 @@ namespace detail
} // namespace detail
NLOHMANN_JSON_NAMESPACE_END
export namespace std
{
using std::hash;
using std::less;
using std::swap;
} // namespace std