Build Failure on mingw

[steph-kraemer]

On v3.2.6, mingw build is failing. Using the toolchain file:

# toolchain-mingw64.cmake
set(CMAKE_SYSTEM_NAME Windows)
set(CMAKE_SYSTEM_PROCESSOR x86_64)

# specify the cross compiler
set(CMAKE_C_COMPILER x86_64-w64-mingw32-gcc)
set(CMAKE_CXX_COMPILER x86_64-w64-mingw32-g++)
set(CMAKE_RC_COMPILER x86_64-w64-mingw32-windres)

# where is the target environment
set(CMAKE_FIND_ROOT_PATH /usr/x86_64-w64-mingw32)

# search for programs in the build host directories
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
# for libraries and headers in the target directories
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

cmake -B build -DCMAKE_TOOLCHAIN_FILE=../../toolchain-mingw64.cmake
cmake --build build

Fails with the error:

[ 84%] Building CXX object src/libdbcppp/CMakeFiles/libdbcppp.dir/SignalImpl.cpp.obj
In file included from /home/stephk/Projects/dbcppp-builder/submodules/dbcppp/src/libdbcppp/SignalImpl.cpp:2:
/home/stephk/Projects/dbcppp-builder/submodules/dbcppp/src/libdbcppp/Helper.h:40:13: fatal error: byteswap.h: No such file or directory
   40 | #   include <byteswap.h>
      |             ^~~~~~~~~~~~
compilation terminated.
gmake[2]: *** [src/libdbcppp/CMakeFiles/libdbcppp.dir/build.make:302: src/libdbcppp/CMakeFiles/libdbcppp.dir/SignalImpl.cpp.obj] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:312: src/libdbcppp/CMakeFiles/libdbcppp.dir/all] Error 2
gmake: *** [Makefile:156: all] Error 2

This can be fixed with the following patch:

diff --git a/src/libdbcppp/Helper.h b/src/libdbcppp/Helper.h
index ef98c1e..2f5999d 100644
--- a/src/libdbcppp/Helper.h
+++ b/src/libdbcppp/Helper.h
@@ -8,7 +8,7 @@
 
 #include "EndianConfig.h"
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) || defined(__MINGW32__)
 #   include <stdlib.h>
 #   define bswap_32(x) _byteswap_ulong(x)
 #   define bswap_64(x) _byteswap_uint64(x)

It works from v3.2.6, but it is failing due to #148 from master branch.