Add CLIPPER2_NO_IOSTREAM build-time option

CPP/CMakeLists.txt

@@ -17,6 +17,7 @@ option(CLIPPER2_HI_PRECISION "Caution: enabling this will compromise performance
 option(CLIPPER2_UTILS "Build utilities" ON)
 option(CLIPPER2_EXAMPLES "Build examples" ON)
 option(CLIPPER2_TESTS "Build tests" ON)
+option(CLIPPER2_NO_IOSTREAM "Disable iostream-using header overloads" OFF)
 option(USE_EXTERNAL_GTEST "Use system-wide installed GoogleTest" OFF)
 option(USE_EXTERNAL_GBENCHMARK "Use the googlebenchmark" OFF)
 option(BUILD_SHARED_LIBS "Build shared libs" OFF)
@@ -69,6 +70,7 @@ if (NOT (CLIPPER2_USINGZ STREQUAL "ONLY"))
     Clipper2 PUBLIC
       CLIPPER2_MAX_DECIMAL_PRECISION=${CLIPPER2_MAX_DECIMAL_PRECISION}
       $<$<BOOL:${CLIPPER2_HI_PRECISION}>:CLIPPER2_HI_PRECISION>
+      $<$<BOOL:${CLIPPER2_NO_IOSTREAM}>:CLIPPER2_NO_IOSTREAM>
   )
 
   target_include_directories(
@@ -102,6 +104,7 @@ if (NOT (CLIPPER2_USINGZ STREQUAL "OFF"))
       USINGZ
       CLIPPER2_MAX_DECIMAL_PRECISION=${CLIPPER2_MAX_DECIMAL_PRECISION}
       $<$<BOOL:${CLIPPER2_HI_PRECISION}>:CLIPPER2_HI_PRECISION>
+      $<$<BOOL:${CLIPPER2_NO_IOSTREAM}>:CLIPPER2_NO_IOSTREAM>
   )
   target_include_directories(
     Clipper2Z PUBLIC 
@@ -130,6 +133,26 @@ set_target_properties(${CLIPPER2_LIBS} PROPERTIES FOLDER Libraries
                                          PUBLIC_HEADER "${CLIPPER2_INC}"
 )
 
+# Compiles the public headers with CLIPPER2_NO_IOSTREAM defined against
+# each shipped library variant. Fails if any iostream usage creeps in
+# outside the macro guards. Always-on (independent of CLIPPER2_NO_IOSTREAM
+# itself); the targets just inherit each library's other PUBLIC
+# definitions (USINGZ, CLIPPER2_HI_PRECISION, ...) via target_link_libraries.
+foreach(_lib IN LISTS CLIPPER2_LIBS)
+  set(_check ${_lib}_no_iostream_check)
+  add_library(${_check} OBJECT Tests/no_iostream_check.cpp)
+  target_link_libraries(${_check} PRIVATE ${_lib})
+  if(NOT CLIPPER2_NO_IOSTREAM)
+    target_compile_definitions(${_check} PRIVATE CLIPPER2_NO_IOSTREAM)
+  endif()
+  if(CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "MSVC")
+    target_compile_options(${_check} PRIVATE /W4 /WX)
+  elseif(CMAKE_CXX_COMPILER_FRONTEND_VARIANT STREQUAL "GNU")
+    target_compile_options(${_check} PRIVATE -Wall -Wextra -Wpedantic -Werror)
+  endif()
+  set_target_properties(${_check} PROPERTIES FOLDER Libraries)
+endforeach()
+
 if(CLIPPER2_UTILS OR CLIPPER2_TESTS OR CLIPPER2_EXAMPLES)
   set(CLIPPER2_UTILS_INC
     Utils/clipper.svg.h

CPP/Clipper2Lib/include/clipper2/clipper.core.h

@@ -14,7 +14,9 @@
 #include <cstdint>
 #include <vector>
 #include <string>
+#ifndef CLIPPER2_NO_IOSTREAM
 #include <iostream>
+#endif
 #include <algorithm>
 #include <numeric>
 #include <cmath>
@@ -166,11 +168,13 @@ namespace Clipper2Lib
 
     void SetZ(const z_type z_value) { z = z_value; }
 
+#ifndef CLIPPER2_NO_IOSTREAM
     friend std::ostream& operator<<(std::ostream& os, const Point& point)
     {
       os << point.x << "," << point.y << "," << point.z;
       return os;
     }
+#endif
 
 #else
 
@@ -203,11 +207,13 @@ namespace Clipper2Lib
       return Point(x * scale, y * scale);
     }
 
+#ifndef CLIPPER2_NO_IOSTREAM
     friend std::ostream& operator<<(std::ostream& os, const Point& point)
     {
       os << point.x << "," << point.y;
       return os;
     }
+#endif
 #endif
 
     friend bool operator==(const Point& a, const Point& b)
@@ -396,10 +402,12 @@ namespace Clipper2Lib
       return result;
     }
 
+#ifndef CLIPPER2_NO_IOSTREAM
     friend std::ostream& operator<<(std::ostream& os, const Rect<T>& rect) {
       os << "(" << rect.left << "," << rect.top << "," << rect.right << "," << rect.bottom << ") ";
       return os;
     }
+#endif
   };
 
   template <typename T1, typename T2>
@@ -498,6 +506,7 @@ namespace Clipper2Lib
     return Rect<T>(xmin, ymin, xmax, ymax);
   }
 
+#ifndef CLIPPER2_NO_IOSTREAM
   template <typename T>
   std::ostream& operator << (std::ostream& outstream, const Path<T>& path)
   {
@@ -518,6 +527,7 @@ namespace Clipper2Lib
       outstream << p;
     return outstream;
   }
+#endif
 
 
   template <typename T1, typename T2>

CPP/Clipper2Lib/include/clipper2/clipper.h

@@ -309,6 +309,7 @@ namespace Clipper2Lib {
       return true;
     }
 
+#ifndef CLIPPER2_NO_IOSTREAM
     static void OutlinePolyPath(std::ostream& os,
       size_t idx, bool isHole, size_t count, const std::string& preamble)
     {
@@ -338,6 +339,7 @@ namespace Clipper2Lib {
         if (pp.Child(i)->Count())
           details::OutlinePolyPathD(os, *pp.Child(i), i, preamble + "  ");
     }
+#endif
 
     template<typename T, typename U>
     inline constexpr void MakePathGeneric(const T an_array,
@@ -377,6 +379,7 @@ namespace Clipper2Lib {
 
   } // end details namespace
 
+#ifndef CLIPPER2_NO_IOSTREAM
   inline std::ostream& operator<< (std::ostream& os, const PolyTree64& pp)
   {
     std::string plural = (pp.Count() == 1) ? " polygon." : " polygons.";
@@ -399,6 +402,7 @@ namespace Clipper2Lib {
     if (!pp.Level()) os << std::endl;
     return os;
   }
+#endif
 
   inline Paths64 PolyTreeToPaths64(const PolyTree64& polytree)
   {

CPP/Tests/no_iostream_check.cpp

@@ -0,0 +1,16 @@
+/*******************************************************************************
+* Author    :  Angus Johnson                                                   *
+* Date      :  3 May 2026                                                      *
+* Website   :  https://www.angusj.com                                          *
+* Copyright :  Angus Johnson 2010-2026                                         *
+* Purpose   :  Build-time check that the public headers compile cleanly with   *
+*              CLIPPER2_NO_IOSTREAM defined.                                   *
+* License   :  https://www.boost.org/LICENSE_1_0.txt                           *
+*******************************************************************************/
+
+#include "clipper2/clipper.h"
+
+namespace {
+Clipper2Lib::Paths64 _p64;
+Clipper2Lib::Rect64  _r64;
+}  // namespace