Make the compare headers self-contained (move comparison_error to its own header)

.github/workflows/ci.yml

@@ -92,7 +92,7 @@ jobs:
           - { compiler: clang-19,  cxxstd: "11,14,17,20,23,2c", os: ubuntu-24.04 }
           - { compiler: clang-20,  cxxstd: "11,14,17,20,23,2c", os: ubuntu-latest, container: "ubuntu:25.04" }
           - { compiler: clang-21,  cxxstd: "11,14,17,20,23,2c", os: ubuntu-latest, container: "ubuntu:26.04" }
-          - { compiler: clang-22,  cxxstd: "11,14,17,20,23,2c", os: ubuntu-latest, container: "ubuntu:26.04" }
+          - { compiler: clang-22,  cxxstd: "11,14,17,20,23,2c", os: ubuntu-latest, container: "ubuntu:26.04", self_contained_headers: "yes" }
           - { compiler: icpx-2025, cxxstd: "11,14,17,20,23,2c", os: ubuntu-latest, container: "intel/oneapi-hpckit:2025.2.2-0-devel-ubuntu24.04" }
           # libc++
           - { name: "Clang w/ sanitizers", sanitize: "yes", stdlib: "libc++",
@@ -283,6 +283,7 @@ jobs:
             ${B2_WRAPPER:-} ./b2 libs/$SELF/test "${ARGS[@]}"
         env:
           UBSAN_OPTIONS: print_stacktrace=1,report_error_type=1
+          BOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS: ${{ matrix.self_contained_headers }}
           BDDE_DISTRO: ${{ matrix.distro }}
           BDDE_EDITION: ${{ matrix.edition }}
           BDDE_ARCH: ${{ matrix.arch }}
@@ -506,7 +507,7 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { os: ubuntu-latest,       build_shared: "ON",  build_type: Debug, generator: "Unix Makefiles" }
+          - { os: ubuntu-latest,       build_shared: "ON",  build_type: Debug, generator: "Unix Makefiles", self_contained_headers: "yes" }
           - { os: ubuntu-latest,       build_shared: "OFF", build_type: Debug, generator: "Unix Makefiles" }
           - { os: windows-2022,        build_shared: "ON",  build_type: Debug, generator: "Visual Studio 17 2022" }
           - { os: windows-2022,        build_shared: "OFF", build_type: Debug, generator: "Visual Studio 17 2022" }
@@ -574,7 +575,7 @@ jobs:
         run: |
             cd "$BOOST_ROOT"
             mkdir __build_cmake_test__ && cd __build_cmake_test__
-            cmake -G "${{ matrix.generator }}" -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=${{ matrix.build_shared }} -DBUILD_TESTING=ON -DBoost_VERBOSE=ON ..
+            cmake -G "${{ matrix.generator }}" -DCMAKE_BUILD_TYPE=${{ matrix.build_type }} -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=${{ matrix.build_shared }} -DBUILD_TESTING=ON -DBoost_VERBOSE=ON ${{ matrix.self_contained_headers && '-DBOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS=ON' || '' }} ..
             cmake --build . --target tests --config ${{ matrix.build_type }} -j3
             ctest --output-on-failure --no-tests=error --build-config ${{ matrix.build_type }}
 

include/boost/numeric/interval/compare/certain.hpp

@@ -11,6 +11,7 @@
 #define BOOST_NUMERIC_INTERVAL_COMPARE_CERTAIN_HPP
 
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 #include <boost/numeric/interval/detail/test_input.hpp>
 
 namespace boost {

include/boost/numeric/interval/compare/lexicographic.hpp

@@ -11,6 +11,7 @@
 #define BOOST_NUMERIC_INTERVAL_COMPARE_LEXICOGRAPHIC_HPP
 
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 #include <boost/numeric/interval/detail/test_input.hpp>
 
 namespace boost {

include/boost/numeric/interval/compare/possible.hpp

@@ -11,6 +11,7 @@
 #define BOOST_NUMERIC_INTERVAL_COMPARE_POSSIBLE_HPP
 
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 #include <boost/numeric/interval/detail/test_input.hpp>
 
 namespace boost {

include/boost/numeric/interval/compare/set.hpp

@@ -11,6 +11,7 @@
 #define BOOST_NUMERIC_INTERVAL_COMPARE_SET_HPP
 
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 #include <boost/numeric/interval/detail/test_input.hpp>
 #include <boost/numeric/interval/utility.hpp>
 

include/boost/numeric/interval/compare/tribool.hpp

@@ -11,6 +11,7 @@
 #define BOOST_NUMERIC_INTERVAL_COMPARE_TRIBOOL_HPP
 
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 #include <boost/numeric/interval/detail/test_input.hpp>
 #include <boost/logic/tribool.hpp>
 

include/boost/numeric/interval/detail/comparison_error.hpp

@@ -0,0 +1,34 @@
+/* Boost interval/detail/comparison_error.hpp file
+ *
+ * Copyright 2002-2003 Hervé Brönnimann, Guillaume Melquiond, Sylvain Pion
+ * Copyright 2026 Sayan Samanta
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or
+ * copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_NUMERIC_INTERVAL_DETAIL_COMPARISON_ERROR_HPP
+#define BOOST_NUMERIC_INTERVAL_DETAIL_COMPARISON_ERROR_HPP
+
+#include <boost/config.hpp>
+#include <stdexcept>
+
+namespace boost {
+namespace numeric {
+namespace interval_lib {
+
+class BOOST_SYMBOL_VISIBLE comparison_error
+  : public std::runtime_error
+{
+public:
+  comparison_error()
+    : std::runtime_error("boost::interval: uncertain comparison")
+  { }
+};
+
+} // namespace interval_lib
+} // namespace numeric
+} // namespace boost
+
+#endif // BOOST_NUMERIC_INTERVAL_DETAIL_COMPARISON_ERROR_HPP

include/boost/numeric/interval/ext/x86_fast_rounding_control.hpp

@@ -17,6 +17,9 @@
 #ifndef BOOST_NUMERIC_INTERVAL_EXT_X86_FAST_ROUNDING_CONTROL_HPP
 #define BOOST_NUMERIC_INTERVAL_EXT_X86_FAST_ROUNDING_CONTROL_HPP
 
+#include <boost/numeric/interval/rounding.hpp>
+#include <boost/numeric/interval/detail/x86_rounding_control.hpp>
+
 namespace boost {
 namespace numeric {
 namespace interval_lib {

include/boost/numeric/interval/interval.hpp

@@ -13,23 +13,11 @@
 #include <stdexcept>
 #include <string>
 #include <boost/numeric/interval/detail/interval_prototype.hpp>
+#include <boost/numeric/interval/detail/comparison_error.hpp>
 
 namespace boost {
 namespace numeric {
 
-namespace interval_lib {
-
-class comparison_error
-  : public std::runtime_error 
-{
-public:
-  comparison_error()
-    : std::runtime_error("boost::interval: uncertain comparison")
-  { }
-};
-
-} // namespace interval_lib
-
 /*
  * interval class
  */

test/CMakeLists.txt

@@ -26,6 +26,27 @@ set(BOOST_TEST_LINK_LIBRARIES Boost::numeric_interval Boost::core)
 
 boost_test(TYPE compile SOURCES integer.cpp)
 
+# Each public header must compile on its own.  These compile-only tests are
+# slow and add little per configuration, so they are off by default and CI
+# turns them on in one job.
+option(BOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS "Test that each public header compiles on its own" OFF)
+
+if(BOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS)
+  set(headers_path ${CMAKE_CURRENT_SOURCE_DIR}/../include/boost/numeric)
+  file(GLOB_RECURSE headers RELATIVE ${headers_path} CONFIGURE_DEPENDS ${headers_path}/*.hpp)
+  list(FILTER headers EXCLUDE REGEX "/detail/")
+  # x86 only by design.
+  if(NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^(x86_64|AMD64|amd64|x86|i[3-6]86)$")
+    list(REMOVE_ITEM headers interval/ext/x86_fast_rounding_control.hpp)
+  endif()
+
+  foreach(h IN LISTS headers)
+    string(MAKE_C_IDENTIFIER "${h}" name)
+    boost_test(TYPE compile NAME self_contained-${name} SOURCES self_contained_header.cpp
+      COMPILE_DEFINITIONS BOOST_NUMERIC_INTERVAL_TEST_HEADER=${h})
+  endforeach()
+endif()
+
 foreach(t add det fmod mul overflow pi pow cmp cmp_exp cmp_lex cmp_set test_float)
   boost_test(TYPE run SOURCES ${t}.cpp)
 endforeach()

test/Jamfile.v2

@@ -22,10 +22,39 @@ project
 
 # bring in rules for testing
 import testing ;
+import os ;
+import path ;
+import regex ;
+
+# Each public header must compile on its own.  These compile-only tests are
+# slow and add little per configuration, so they are off by default; set the
+# BOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS environment variable to
+# run them.
+path-constant INTERVAL_INCLUDE_DIR : ../include ;
+
+local self_contained_tests ;
+if [ os.environ BOOST_NUMERIC_INTERVAL_TEST_SELF_CONTAINED_HEADERS ]
+{
+  local headers_path = [ path.make $(INTERVAL_INCLUDE_DIR)/boost/numeric ] ;
+  for local file in [ path.glob-tree $(headers_path) : *.hpp : detail ]
+  {
+    local h = [ path.relative-to $(headers_path) $(file) ] ;
+    local requirements = <define>BOOST_NUMERIC_INTERVAL_TEST_HEADER=$(h) <dependency>$(file) ;
+    if $(h) = interval/ext/x86_fast_rounding_control.hpp
+    {
+      # x86 only by design.
+      requirements += [ check-target-builds /boost/architecture//x86 : : <build>no ] ;
+    }
+    self_contained_tests += [ compile self_contained_header.cpp
+      : $(requirements)
+      : [ regex.replace self_contained-$(h) "[/.]" "-" ] ] ;
+  }
+}
 
 {
   test-suite numeric/interval :
     [ compile integer.cpp ]
+    $(self_contained_tests)
 
     [ run add.cpp      ]
     [ run det.cpp      ]

test/self_contained_header.cpp

@@ -0,0 +1,20 @@
+/* Boost test/self_contained_header.cpp
+ * test that a public header compiles when included on its own
+ *
+ * The header is given relative to boost/numeric by the build system in
+ * BOOST_NUMERIC_INTERVAL_TEST_HEADER, e.g. interval/compare/certain.hpp.
+ *
+ * Copyright 2026 Sayan Samanta
+ *
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or
+ * copy at http://www.boost.org/LICENSE_1_0.txt)
+ */
+
+#define BOOST_NUMERIC_INTERVAL_TEST_INCLUDE_HEADER() <boost/numeric/BOOST_NUMERIC_INTERVAL_TEST_HEADER>
+
+#include BOOST_NUMERIC_INTERVAL_TEST_INCLUDE_HEADER()
+
+int main() {
+  return 0;
+}