Building Swift code under Windows could be tricky. Let us disable it for

now.

Author: lemire

benchmarks/CMakeLists.txt

@@ -77,5 +77,10 @@ endif()
 target_link_libraries(benchmark PUBLIC dragonbox::dragonbox_to_chars)
 target_link_libraries(benchmark PUBLIC dragon_schubfach_lib)
 target_link_libraries(benchmark PUBLIC dragon4_lib)
-target_link_libraries(benchmark PUBLIC swift_lib)
+if(TARGET swift_lib)
+    target_link_libraries(benchmark PUBLIC swift_lib)
+    target_compile_definitions(benchmark PUBLIC SWIFT_LIB_SUPPORTED=1)
+else(TARGET swift_lib)
+    target_compile_definitions(benchmark PUBLIC SWIFT_LIB_SUPPORTED=0)
+endif(TARGET swift_lib)
 target_include_directories(benchmark PUBLIC ${grisu-exact_SOURCE_DIR})

benchmarks/algorithms.h

@@ -32,7 +32,9 @@
 #include "ryu/ryu.h"
 #include "schubfach_32.h"
 #include "schubfach_64.h"
+#if SWIFT_LIB_SUPPORTED
 #include "swift/Runtime/SwiftDtoa.h"
+#endif
 #if (__SIZEOF_INT128__ == 16) && (defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER))
 #include "yy_double.h"
 #define YY_DOUBLE_SUPPORTED 1
@@ -235,10 +237,15 @@ int double_conversion(T d, std::span<char>& buffer) {
 
 template<arithmetic_float T>
 int swiftDtoa(T d, std::span<char>& buffer) {
+#if SWIFT_LIB_SUPPORTED
   if constexpr (std::is_same_v<T, float>)
     return swift_dtoa_optimal_float(d, buffer.data(), buffer.size());
   else
     return swift_dtoa_optimal_double(d, buffer.data(), buffer.size());
+#else
+  std::cerr << "swift code not supported" << std::endl;
+  std::abort();
+#endif
 }
 
 template<arithmetic_float T>

benchmarks/benchmark.cpp

@@ -197,7 +197,7 @@ int main(int argc, char **argv) {
       args[Benchmarks::ABSEIL]            = { "abseil"            , Benchmarks::abseil<T>            , ABSEIL_SUPPORTED };
       args[Benchmarks::STD_TO_CHARS]      = { "std::to_chars"     , Benchmarks::std_to_chars<T>      , TO_CHARS_SUPPORTED };
       args[Benchmarks::GRISU3]            = { "grisu3"            , Benchmarks::grisu3<T>            , true };
-      args[Benchmarks::SWIFT_DTOA]        = { "SwiftDtoa"         , Benchmarks::swiftDtoa<T>         , true };
+      args[Benchmarks::SWIFT_DTOA]        = { "SwiftDtoa"         , Benchmarks::swiftDtoa<T>         , SWIFT_LIB_SUPPORTED };
       args[Benchmarks::YY_DOUBLE]         = { "yy_double"         , Benchmarks::yy_double<T>         , YY_DOUBLE_SUPPORTED };
       return args;
     };

dependencies/CMakeLists.txt

@@ -101,26 +101,29 @@ target_include_directories(dragon4_lib PUBLIC
     ${dragon4_SOURCE_DIR}
 )
 
-FetchContent_Declare(
-        swift
-        GIT_REPOSITORY https://github.com/swiftlang/swift.git
-        GIT_TAG 6a862d2eb7128ff1f317b07e8ad1a6da939775f3
-        GIT_SHALLOW TRUE
-)
-FetchContent_GetProperties(swift)
-if(NOT swift)
-  FetchContent_Populate(swift)  # Downloads code to ${dragon4_SOURCE_DIR}
-endif()
-set(swift_SOURCE_DIR ${swift_SOURCE_DIR} PARENT_SCOPE)
-add_library(swift_lib STATIC
-    ${swift_SOURCE_DIR}/stdlib/public/runtime/SwiftDtoa.cpp
-)
-if(MATH_LIBRARY)
-    target_link_libraries(swift_lib PUBLIC ${MATH_LIBRARY})
-endif()
-target_include_directories(swift_lib PUBLIC
-    ${swift_SOURCE_DIR}/include
-)
+# Swift code may not build under Windows without extra care.
+if(NOT WIN32)
+        FetchContent_Declare(
+                swift
+                GIT_REPOSITORY https://github.com/swiftlang/swift.git
+                GIT_TAG 6a862d2eb7128ff1f317b07e8ad1a6da939775f3
+                GIT_SHALLOW TRUE
+        )
+        FetchContent_GetProperties(swift)
+        if(NOT swift)
+                FetchContent_Populate(swift)  # Downloads code to ${dragon4_SOURCE_DIR}
+        endif()
+        set(swift_SOURCE_DIR ${swift_SOURCE_DIR} PARENT_SCOPE)
+        add_library(swift_lib STATIC
+                ${swift_SOURCE_DIR}/stdlib/public/runtime/SwiftDtoa.cpp
+        )
+        if(MATH_LIBRARY)
+                target_link_libraries(swift_lib PUBLIC ${MATH_LIBRARY})
+        endif()
+        target_include_directories(swift_lib PUBLIC
+           ${swift_SOURCE_DIR}/include
+        )
+endif(NOT WIN32)
 
 FetchContent_Declare(
         drachennest # for schubfach