lib: zstd: cmake: only require a CXX compiler when tests are build

See: facebook/zstd#4357
Signed-off-by: Thomas Devoogdt <[email protected]>

Author: ThomasDevoogdt

lib/zstd-1.5.7/build/cmake/CMakeLists.txt

@@ -37,7 +37,6 @@ project(zstd
   VERSION "${ZSTD_FULL_VERSION}"
   LANGUAGES C   # Main library is in C
             ASM # And ASM
-            CXX # Testing contributed code also utilizes CXX
   )
 
 message(STATUS "ZSTD VERSION: ${zstd_VERSION}")
@@ -54,12 +53,6 @@ endif()
 
 include(GNUInstallDirs)
 
-#-----------------------------------------------------------------------------
-# Add extra compilation flags
-#-----------------------------------------------------------------------------
-include(AddZstdCompilationFlags)
-ADD_ZSTD_COMPILATION_FLAGS()
-
 # Always hide XXHash symbols
 add_definitions(-DXXH_NAMESPACE=ZSTD_)
 
@@ -123,6 +116,19 @@ if (MSVC)
     option(ZSTD_USE_STATIC_RUNTIME "LINK TO STATIC RUN-TIME LIBRARIES" OFF)
 endif ()
 
+# Enable C++ support for testing.
+set(ZSTD_ENABLE_CXX ${ZSTD_BUILD_TESTS})
+
+if(ZSTD_ENABLE_CXX)
+    enable_language(CXX)
+endif()
+
+#-----------------------------------------------------------------------------
+# Add extra compilation flags
+#-----------------------------------------------------------------------------
+include(AddZstdCompilationFlags)
+ADD_ZSTD_COMPILATION_FLAGS(ON ZSTD_ENABLE_CXX ON) # C CXX LD
+
 #-----------------------------------------------------------------------------
 # External dependencies
 #-----------------------------------------------------------------------------

lib/zstd-1.5.7/build/cmake/CMakeModules/AddZstdCompilationFlags.cmake

@@ -49,7 +49,7 @@ function(EnableCompilerFlag _flag _C _CXX _LD)
     endif ()
 endfunction()
 
-macro(ADD_ZSTD_COMPILATION_FLAGS)
+macro(ADD_ZSTD_COMPILATION_FLAGS _C _CXX _LD)
     # We set ZSTD_HAS_NOEXECSTACK if we are certain we've set all the required
     # compiler flags to mark the stack as non-executable.
     set(ZSTD_HAS_NOEXECSTACK false)
@@ -63,26 +63,26 @@ macro(ADD_ZSTD_COMPILATION_FLAGS)
         # EnableCompilerFlag("-std=c99" true false)   # Set C compilation to c99 standard
         if (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND MSVC)
             # clang-cl normally maps -Wall to -Weverything.
-            EnableCompilerFlag("/clang:-Wall" true true false)
+            EnableCompilerFlag("/clang:-Wall" _C _CXX false)
         else ()
-            EnableCompilerFlag("-Wall" true true false)
+            EnableCompilerFlag("-Wall" _C _CXX false)
         endif ()
-        EnableCompilerFlag("-Wextra" true true false)
-        EnableCompilerFlag("-Wundef" true true false)
-        EnableCompilerFlag("-Wshadow" true true false)
-        EnableCompilerFlag("-Wcast-align" true true false)
-        EnableCompilerFlag("-Wcast-qual" true true false)
-        EnableCompilerFlag("-Wstrict-prototypes" true false false)
+        EnableCompilerFlag("-Wextra" _C _CXX false)
+        EnableCompilerFlag("-Wundef" _C _CXX false)
+        EnableCompilerFlag("-Wshadow" _C _CXX false)
+        EnableCompilerFlag("-Wcast-align" _C _CXX false)
+        EnableCompilerFlag("-Wcast-qual" _C _CXX false)
+        EnableCompilerFlag("-Wstrict-prototypes" _C false false)
         # Enable asserts in Debug mode
         if (CMAKE_BUILD_TYPE MATCHES "Debug")
-            EnableCompilerFlag("-DDEBUGLEVEL=1" true true false)
+            EnableCompilerFlag("-DDEBUGLEVEL=1" _C _CXX false)
         endif ()
         # Add noexecstack flags
         # LDFLAGS
-        EnableCompilerFlag("-Wl,-z,noexecstack" false false true)
+        EnableCompilerFlag("-Wl,-z,noexecstack" false false _LD)
         # CFLAGS & CXXFLAGS
-        EnableCompilerFlag("-Qunused-arguments" true true false)
-        EnableCompilerFlag("-Wa,--noexecstack" true true false)
+        EnableCompilerFlag("-Qunused-arguments" _C _CXX false)
+        EnableCompilerFlag("-Wa,--noexecstack" _C _CXX false)
         # NOTE: Using 3 nested ifs because the variables are sometimes
         # empty if the condition is false, and sometimes equal to false.
         # This implicitly converts them to truthy values. There may be
@@ -99,15 +99,15 @@ macro(ADD_ZSTD_COMPILATION_FLAGS)
 
         set(ACTIVATE_MULTITHREADED_COMPILATION "ON" CACHE BOOL "activate multi-threaded compilation (/MP flag)")
         if (CMAKE_GENERATOR MATCHES "Visual Studio" AND ACTIVATE_MULTITHREADED_COMPILATION)
-            EnableCompilerFlag("/MP" true true false)
+            EnableCompilerFlag("/MP" _C _CXX false)
         endif ()
 
         # UNICODE SUPPORT
-        EnableCompilerFlag("/D_UNICODE" true true false)
-        EnableCompilerFlag("/DUNICODE" true true false)
+        EnableCompilerFlag("/D_UNICODE" _C _CXX false)
+        EnableCompilerFlag("/DUNICODE" _C _CXX false)
         # Enable asserts in Debug mode
         if (CMAKE_BUILD_TYPE MATCHES "Debug")
-            EnableCompilerFlag("/DDEBUGLEVEL=1" true true false)
+            EnableCompilerFlag("/DDEBUGLEVEL=1" _C _CXX false)
         endif ()
     endif ()