cmake: Fix flex version check for overriding the register keyword

[lazka]

In #11113 a check was added to override the "register" keyword for older versions of flex. The check was added before the find_package() call which resulted in the workaround being active for any version of flex. This breaks the build with recent mingw-w64 which uses "register" in its headers.

Fix by moving the version check after the find_package() call.

[lazka]

@albert-github

[albert-github]

@lazka

• What kind of error messages do you get?
• Which version of cmake and flex are you using
• What is the output of your initial cmake run (the configuration run).

[lazka]

• What kind of error messages do you get?

https://sourceforge.net/p/mingw-w64/mailman/message/59112743/

For completeness:

On Fri, 13 Dec 2024, Jacek Caban wrote:

>
> This change is based on Wine's winnt.h implementation. Using a register
> variable for NtCurrentTeb
> allows the compiler to optimize the access more effectively.
> ---
>  mingw-w64-headers/include/winnt.h | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
>
> diff --git a/mingw-w64-headers/include/winnt.h b/mingw-w64-headers/include/winnt.h
> index 96a610c1d..499f72219 100644
> --- a/mingw-w64-headers/include/winnt.h
> +++ b/mingw-w64-headers/include/winnt.h
> @@ -10211,11 +10211,10 @@ typedef DWORD (WINAPI *PRTL_RUN_ONCE_INIT_FN)(PRTL_RUN_ONCE, PVOID, PVOID *);
>      PVOID GetFiberData(VOID);
>
>  #if defined (__aarch64__) || defined(__arm64ec__)
> +    register struct _TEB *__mingw_current_teb __asm__("x18");
>      FORCEINLINE struct _TEB *NtCurrentTeb(VOID)
>      {
> -        struct _TEB *teb;
> -        __asm ("mov %0, x18" : "=r" (teb));
> -        return teb;
> +        return __mingw_current_teb;
>      }
>      FORCEINLINE PVOID GetCurrentFiber(VOID)
>      {

I'm not sure, but I'm guessing this change is causing an error building
doxygen in
https://github.com/msys2-arm/msys2-autobuild/actions/runs/12531144362/job/34948452159?check_suite_focus=true#step:11:1036

  ld.lld: error: duplicate symbol: x18
  >>> defined at addon/doxyparse/CMakeFiles/doxyparse.dir/doxyparse.cpp.obj
  >>> defined at libdoxymain.a(dir.cpp.obj)

  ld.lld: error: duplicate symbol: x18
  >>> defined at addon/doxyparse/CMakeFiles/doxyparse.dir/doxyparse.cpp.obj
  >>> defined at libdoxycfg.a(portable.cpp.obj)

  ld.lld: error: duplicate symbol: x18
  >>> defined at addon/doxyparse/CMakeFiles/doxyparse.dir/doxyparse.cpp.obj
  >>> defined at libdoxymain.a(fileinfo.cpp.obj)

  ld.lld: error: duplicate symbol: x18

  >>> defined at addon/doxyparse/CMakeFiles/doxyparse.dir/doxyparse.cpp.obj

  >>> defined at libdoxycfg.a(trace.cpp.obj)

• Which version of cmake and flex are you using

$ cmake --version
cmake version 3.31.3
$ flex --version
flex 2.6.4

• What is the output of your initial cmake run (the configuration run).

$ cmake . -Wno-dev
-- Building for: Ninja
-- The C compiler identification is Clang 19.1.6
-- The CXX compiler identification is Clang 19.1.6
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/msys64/clang64/bin/cc.exe - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/msys64/clang64/bin/c++.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Using Cmake version 3.31.3
-- Found Python: C:/Python312/python.exe (found version "3.12.7") found components: Interpreter
-- Found FLEX: C:/msys64/usr/bin/flex.exe (found version "2.6.4")
-- Found BISON: C:/msys64/usr/bin/bison.exe (found version "3.8.2")
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Found Iconv: C:/msys64/clang64/lib/libiconv.dll.a (found version "1.18")
-- Build spdlog: 1.14.1
-- Build type: Release
-- The javacc executable not found, using existing files
-- The generateDS executable not found, using existing files
-- Configuring done (3.2s)
-- Generating done (0.1s)
-- Build files have been written to: C:/msys64/home/user/git/doxygen

[albert-github]

The test indeed looks like to be at the completely wrong place.

[lazka]

Thank you!