Run host-toolchain CI jobs on ubuntu-26.04

GitHub moves ubuntu-latest to Ubuntu 26.04 between 2026-10-19 and
2026-11-19 (actions/runner-images#14748). Run the jobs that use the
runner's own compilers and tools on ubuntu-26.04 now to find breakage
before the rollout. Container jobs are unaffected.

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

.github/workflows/check_amalgamation.yml

@@ -37,7 +37,7 @@ jobs:
           path: pr/
 
   check:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     env:
       MAIN_DIR: ${{ github.workspace }}/main
       INCLUDE_DIR: ${{ github.workspace }}/main/single_include/nlohmann

.github/workflows/codeql-analysis.yml

@@ -21,7 +21,7 @@ permissions:
 jobs:
   CodeQL-Build:
 
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     permissions:
       security-events: write
 

.github/workflows/semgrep.yml

@@ -33,7 +33,7 @@ jobs:
       security-events: write # for github/codeql-action/upload-sarif to upload SARIF results
       actions: read # only required for a private repository by github/codeql-action/upload-sarif to get the Action run status
     name: Scan
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1

.github/workflows/ubuntu.yml

@@ -32,7 +32,7 @@ jobs:
         run: cmake --build build --target ci_test_gcc
 
   ci_meson_install:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
@@ -77,7 +77,7 @@ jobs:
           cmake --build build-import-split
 
   ci_infer:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
@@ -106,7 +106,7 @@ jobs:
           if-no-files-found: ignore
 
   ci_static_analysis_ubuntu:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     strategy:
       matrix:
         target: [ci_test_single_header, ci_cppcheck, ci_cpplint, ci_reproducible_tests, ci_non_git_tests, ci_offline_testdata, ci_reuse_compliance, ci_test_valgrind]
@@ -175,7 +175,7 @@ jobs:
         run: cmake --build build --target ${{ matrix.target }}
 
   ci_test_coverage:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
@@ -430,7 +430,7 @@ jobs:
         run: cmake --build build --target ci_nvhpc
 
   ci_emscripten:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     steps:
       - name: Harden Runner
         uses: step-security/harden-runner@ccd8616d44fd3846e67624a50d5aad6d37bf2d25 # v2.22.1
@@ -450,7 +450,7 @@ jobs:
         run: cmake --build build
 
   ci_test_documentation:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-26.04
     strategy:
       matrix:
         target: [ci_test_examples, ci_test_build_documentation, ci_test_documentation_mermaid]

docs/mkdocs/docs/community/quality_assurance.md

@@ -135,9 +135,6 @@ Note: Some modern features (like C++20 ranges or filesystem support) may be disa
   headers are included.
 - [x] On Windows, the library is compiled with `<Windows.h>` being included to detect and avoid common bugs (see
   [`unit-windows_h.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-windows_h.cpp)).
-- [x] The library is compiled with Qt's keyword macros (`slots`, `signals`, `emit`, `foreach`, `forever`) being defined
-  to make sure it does not use them as identifiers (see
-  [`unit-qt_keywords.cpp`](https://github.com/nlohmann/json/blob/develop/tests/src/unit-qt_keywords.cpp)).
 - [x] The library is compiled with exceptions disabled to support alternative means of error handling.
 
 ## Stable public API

include/nlohmann/detail/json_pointer.hpp

@@ -525,7 +525,7 @@ class json_pointer
             {}
         };
 
-        std::vector<slot> table;
+        std::vector<slot> slots;
         std::size_t used = 0;
 
         static std::size_t hash_of(std::size_t parent, const string_t& token) noexcept
@@ -540,19 +540,19 @@ class json_pointer
 
         void grow()
         {
-            std::vector<slot> old(table.size() * 2);
-            old.swap(table);
-            const std::size_t mask = table.size() - 1;
+            std::vector<slot> old(slots.size() * 2);
+            old.swap(slots);
+            const std::size_t mask = slots.size() - 1;
             for (const auto& s : old)
             {
                 if (s.token != nullptr)
                 {
                     std::size_t i = s.hash & mask;
-                    while (table[i].token != nullptr)
+                    while (slots[i].token != nullptr)
                     {
                         i = (i + 1) & mask;
                     }
-                    table[i] = s;
+                    slots[i] = s;
                 }
             }
         }
@@ -565,7 +565,7 @@ class json_pointer
 
         // start with the empty prefix only
         prefix_tree()
-            : table(16)
+            : slots(16)
             , parent(1, 0)
             , is_array(1, false)
         {}
@@ -575,20 +575,20 @@ class json_pointer
         std::size_t add_child(std::size_t id, const string_t& reference_token)
         {
             const std::size_t hash = hash_of(id, reference_token);
-            const std::size_t mask = table.size() - 1;
+            const std::size_t mask = slots.size() - 1;
             std::size_t i = hash & mask;
-            while (table[i].token != nullptr)
+            while (slots[i].token != nullptr)
             {
-                if (table[i].hash == hash && table[i].parent == id && *table[i].token == reference_token)
+                if (slots[i].hash == hash && slots[i].parent == id && *slots[i].token == reference_token)
                 {
-                    return table[i].id;
+                    return slots[i].id;
                 }
                 i = (i + 1) & mask;
             }
 
             // new prefix
             const std::size_t child = parent.size();
-            table[i] = slot(hash, id, &reference_token, child);
+            slots[i] = slot(hash, id, &reference_token, child);
             if (reference_token == "0")
             {
                 is_array[id] = true;
@@ -597,7 +597,7 @@ class json_pointer
             is_array.push_back(false);
 
             // keep the load factor below 1/2
-            if (++used * 2 > table.size())
+            if (++used * 2 > slots.size())
             {
                 grow();
             }

single_include/nlohmann/json.hpp

@@ -21497,7 +21497,7 @@ class json_pointer
             {}
         };
 
-        std::vector<slot> table;
+        std::vector<slot> slots;
         std::size_t used = 0;
 
         static std::size_t hash_of(std::size_t parent, const string_t& token) noexcept
@@ -21512,19 +21512,19 @@ class json_pointer
 
         void grow()
         {
-            std::vector<slot> old(table.size() * 2);
-            old.swap(table);
-            const std::size_t mask = table.size() - 1;
+            std::vector<slot> old(slots.size() * 2);
+            old.swap(slots);
+            const std::size_t mask = slots.size() - 1;
             for (const auto& s : old)
             {
                 if (s.token != nullptr)
                 {
                     std::size_t i = s.hash & mask;
-                    while (table[i].token != nullptr)
+                    while (slots[i].token != nullptr)
                     {
                         i = (i + 1) & mask;
                     }
-                    table[i] = s;
+                    slots[i] = s;
                 }
             }
         }
@@ -21537,7 +21537,7 @@ class json_pointer
 
         // start with the empty prefix only
         prefix_tree()
-            : table(16)
+            : slots(16)
             , parent(1, 0)
             , is_array(1, false)
         {}
@@ -21547,20 +21547,20 @@ class json_pointer
         std::size_t add_child(std::size_t id, const string_t& reference_token)
         {
             const std::size_t hash = hash_of(id, reference_token);
-            const std::size_t mask = table.size() - 1;
+            const std::size_t mask = slots.size() - 1;
             std::size_t i = hash & mask;
-            while (table[i].token != nullptr)
+            while (slots[i].token != nullptr)
             {
-                if (table[i].hash == hash && table[i].parent == id && *table[i].token == reference_token)
+                if (slots[i].hash == hash && slots[i].parent == id && *slots[i].token == reference_token)
                 {
-                    return table[i].id;
+                    return slots[i].id;
                 }
                 i = (i + 1) & mask;
             }
 
             // new prefix
             const std::size_t child = parent.size();
-            table[i] = slot(hash, id, &reference_token, child);
+            slots[i] = slot(hash, id, &reference_token, child);
             if (reference_token == "0")
             {
                 is_array[id] = true;
@@ -21569,7 +21569,7 @@ class json_pointer
             is_array.push_back(false);
 
             // keep the load factor below 1/2
-            if (++used * 2 > table.size())
+            if (++used * 2 > slots.size())
             {
                 grow();
             }

tests/src/unit-qt_keywords.cpp

@@ -1,67 +0,0 @@
-//     __ _____ _____ _____
-//  __|  |   __|     |   | |  JSON for Modern C++ (supporting code)
-// |  |  |__   |  |  | | | |  version 3.12.0
-// |_____|_____|_____|_|___|  https://github.com/nlohmann/json
-//
-// SPDX-FileCopyrightText: 2013-2026 Niels Lohmann <https://nlohmann.me>
-// SPDX-License-Identifier: MIT
-
-#include "doctest_compatibility.h"
-
-// Qt defines its keywords as macros (see qtmetamacros.h and qforeach.h) unless
-// QT_NO_KEYWORDS is defined, and it is common to include Qt headers before this
-// library; it must therefore not use these words as identifiers (see #5865)
-#define slots
-#define signals public
-#define emit
-#define Q_FOREACH(variable, container) for (variable : container) // NOLINT(bugprone-macro-parentheses): variable is a declaration, as in Qt
-#define foreach Q_FOREACH
-#define forever for (;;)
-
-#include <nlohmann/json.hpp>
-using nlohmann::json;
-
-TEST_CASE("Qt keyword macros")
-{
-    SECTION("parse and dump")
-    {
-        const json j = json::parse(R"({"a": [1, 2.5, "x", null, true]})");
-        CHECK(j.dump() == R"({"a":[1,2.5,"x",null,true]})");
-    }
-
-    SECTION("flatten and unflatten")
-    {
-        const json j = {{"a", {{"b", {1, 2}}, {"c", "d"}}}, {"e", nullptr}};
-        CHECK(j.flatten().unflatten() == j);
-    }
-
-    SECTION("JSON pointer")
-    {
-        json j = {{"a", {{"b", {1, 2}}}}};
-        CHECK(j.at(json::json_pointer("/a/b/1")) == 2);
-        j[json::json_pointer("/a/c")] = 3;
-        CHECK(j.contains(json::json_pointer("/a/c")));
-    }
-
-    SECTION("binary formats")
-    {
-        const json j = {{"a", {1, 2, 3}}, {"b", "c"}};
-        CHECK(json::from_cbor(json::to_cbor(j)) == j);
-        CHECK(json::from_msgpack(json::to_msgpack(j)) == j);
-        CHECK(json::from_ubjson(json::to_ubjson(j)) == j);
-        CHECK(json::from_bjdata(json::to_bjdata(j)) == j);
-        CHECK(json::from_bson(json::to_bson(j)) == j);
-    }
-
-    SECTION("patch and diff")
-    {
-        const json source = {{"a", 1}, {"b", {1, 2}}};
-        const json target = {{"a", 2}, {"c", "d"}};
-        CHECK(source.patch(json::diff(source, target)) == target);
-    }
-}
-
-// testing for the macros also keeps -Wunused-macros from rejecting them
-#if !defined(slots) || !defined(signals) || !defined(emit) || !defined(Q_FOREACH) || !defined(foreach) || !defined(forever)
-    #error "the Qt keyword macros must stay defined for the tests above"
-#endif