Build and use double-conversion library shipped by Qt when needed

Some Linux distros might not have a double-conversion library. Because
it is such an essential library for QtCore, compile and use the
the copy of the library bundled with Qt.

Also change library name to be a proper target with double colons,
so that in case the library is not found for some reason, the CMake
configure step would fail, instead of failing at link time.

Task-number: QTBUG-74133
Change-Id: I9f3b4298ae6e952891a7a89541d46878176bf1ce
Fixes: QTBUG-75891
Reviewed-by: Liang Qi <liang.qi@qt.io>
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

4 files changed, 40 insertions, 7 deletions

diff --git a/cmake/FindWrapDoubleConversion.cmake b/cmake/FindWrapDoubleConversion.cmake
index cfb70a0981..1164f6ba44 100644
--- a/cmake/FindWrapDoubleConversion.cmake
+++ b/cmake/FindWrapDoubleConversion.cmake
@@ -1,16 +1,17 @@
-include(CheckCXXSourceCompiles)
-
-add_library(WrapDoubleConversion INTERFACE IMPORTED)
+add_library(WrapDoubleConversion::WrapDoubleConversion INTERFACE IMPORTED)
 
 find_package(double-conversion)
 if (double-conversion_FOUND)
     include(FeatureSummary)
     set_package_properties(double-conversion PROPERTIES TYPE REQUIRED)
-    target_link_libraries(WrapDoubleConversion INTERFACE double-conversion::double-conversion)
+    target_link_libraries(WrapDoubleConversion::WrapDoubleConversion
+                          INTERFACE double-conversion::double-conversion)
     set(WrapDoubleConversion_FOUND 1)
     return()
 endif()
 
+include(CheckCXXSourceCompiles)
+
 check_cxx_source_compiles("
 #include <stdio.h>
 #include <locale.h>
@@ -36,8 +37,17 @@ int main(int argc, char *argv[]) {
     return 0;
 }" HAVE_SPRINTF_L)
 
+# In a static build, we need to find the package to bring the target into scope.
+find_package(QtDoubleConversion QUIET)
+
 if (HAVE__SPRINTF_L OR HAVE_SPRINTF_L)
-    target_compile_definitions(WrapDoubleConversion INTERFACE QT_NO_DOUBLECONVERSION)
+    target_compile_definitions(WrapDoubleConversion::WrapDoubleConversion
+                               INTERFACE QT_NO_DOUBLECONVERSION)
+    set(WrapDoubleConversion_FOUND 1)
+elseif(TARGET QtDoubleConversion)
+    # If a Config package wasn't found, and the C++ library doesn't contain the necessary functions,
+    # use the library bundled with Qt.
+    target_link_libraries(WrapDoubleConversion::WrapDoubleConversion INTERFACE QtDoubleConversion)
     set(WrapDoubleConversion_FOUND 1)
 else()
     set(WrapDoubleConversion_FOUND 0)
diff --git a/src/3rdparty/CMakeLists.txt b/src/3rdparty/CMakeLists.txt
index 77c4970f49..d3b30fea65 100644
--- a/src/3rdparty/CMakeLists.txt
+++ b/src/3rdparty/CMakeLists.txt
@@ -1,2 +1,3 @@
 add_subdirectory(tinycbor)
 add_subdirectory(harfbuzz)
+add_subdirectory(double-conversion)
diff --git a/src/3rdparty/double-conversion/CMakeLists.txt b/src/3rdparty/double-conversion/CMakeLists.txt
new file mode 100644
index 0000000000..7450bc48ec
--- /dev/null
+++ b/src/3rdparty/double-conversion/CMakeLists.txt
@@ -0,0 +1,21 @@
+# special case begin
+
+add_library(QtDoubleConversion STATIC
+    ${CMAKE_CURRENT_SOURCE_DIR}/bignum.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/bignum-dtoa.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/cached-powers.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/diy-fp.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/double-conversion.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/fast-dtoa.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/fixed-dtoa.cc
+    ${CMAKE_CURRENT_SOURCE_DIR}/strtod.cc
+    )
+
+target_include_directories(QtDoubleConversion PUBLIC
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/..>
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include/double-conversion>
+    )
+
+qt_install_3rdparty_library(QtDoubleConversion)
+# special case end
diff --git a/src/corelib/CMakeLists.txt b/src/corelib/CMakeLists.txt
index 59ad7dcdd6..cae1e98111 100644
--- a/src/corelib/CMakeLists.txt
+++ b/src/corelib/CMakeLists.txt
@@ -2,7 +2,8 @@
 
 # special case begin
 qt_find_package(Threads PROVIDED_TARGETS Threads::Threads)
-qt_find_package(WrapDoubleConversion REQUIRED PROVIDED_TARGETS WrapDoubleConversion)
+qt_find_package(WrapDoubleConversion REQUIRED
+                                     PROVIDED_TARGETS WrapDoubleConversion::WrapDoubleConversion)
 
 if (NOT WrapDoubleConversion_FOUND)
     message(FATAL_ERROR "Your C library does not provide \
@@ -231,7 +232,7 @@ add_qt_module(Core
         QtHarfBuzz # special case
         Threads::Threads # special case
         tinycbor # special case
-        WrapDoubleConversion # special case
+        WrapDoubleConversion::WrapDoubleConversion # special case
     PUBLIC_LIBRARIES  # special case:
         Qt::Platform # special case:
     DISABLE_AUTOGEN_TOOLS # special case: