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Remove the GCC C++20 -Wignored-attributes pragma in json.hpp

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The pragma (added in #5164) claimed to work around the C++ modules
redefinition errors of #5103, but #5103 is about hard errors (e.g.
"redefinition of std::__is_constant_evaluated()", conflicting
std::integral_constant) that ignoring a warning cannot suppress; they
are traced to GCC PR 124430 and reproduce with <map> or <string>
instead of json.hpp too. A GCC 16.2 -std=gnu++20 -fmodules build
following #5103's repro steps still fails with the pragma in place,
and a build of all test TUs with GCC_CXXFLAGS (which enable
-Wignored-attributes) and the pragma removed produces no such
warning. The block only hid a warning class from GCC C++20 users
while suggesting #5103 was handled.

Overlaps #5610, whose hunks touch the closing half of this pragma to
insert the json_literals.hpp include.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

#5725 item 9
This commit is contained in:
Niels Lohmann
2026-09-30 17:58:51 +02:00
parent 6f3b7c05c2
commit f257ac3373
2 changed files with 0 additions and 30 deletions
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include/nlohmann/json.hpp
-15
View File
@@ -18,16 +18,6 @@
#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, none_of
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <functional> // hash, less
@@ -6619,9 +6609,4 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
#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
View File
@@ -18,16 +18,6 @@
#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, none_of
#include <cstddef> // nullptr_t, ptrdiff_t, size_t
#include <functional> // hash, less
@@ -32919,9 +32909,4 @@ struct formatter<nlohmann::NLOHMANN_BASIC_JSON_TPL, char> // NOLINT(cert-dcl58-c
// 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_