[PATCH v2] meson.build: Use -Wno-undef only for SDL2 versions that need it

[Thomas Huth <thuth@redhat.com>]

There is no need to disable this useful compiler warning for
all versions of the SDL. Unfortunately, various versions are
buggy (beside SDL 2.0.8, the version 2.26.0 and 2.26.1 are
broken, too, see https://github.com/libsdl-org/SDL/issues/6619 ),
but we can use a simple compiler check to see whether we need
the -Wno-undef or not.

This also enables the printing of the version number with
good versions of the SDL in the summary of the meson output
again.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 v2: Compile test code instead of hard-coding the version number

 meson.build | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/meson.build b/meson.build
index a61d3e9b06..a4c69616c3 100644
--- a/meson.build
+++ b/meson.build
@@ -1273,10 +1273,16 @@ if not get_option('sdl').auto() or have_system
   sdl_image = not_found
 endif
 if sdl.found()
-  # work around 2.0.8 bug
-  sdl = declare_dependency(compile_args: '-Wno-undef',
-                           dependencies: sdl,
-                           version: sdl.version())
+  # Some versions of SDL have problems with -Wundef
+  if not cc.compiles('''
+                     #include <SDL.h>
+                     #include <SDL_syswm.h>
+                     int main(int argc, char *argv[]) { return 0; }
+                     ''', dependencies: sdl, args: '-Wundef')
+    sdl = declare_dependency(compile_args: '-Wno-undef',
+                             dependencies: sdl,
+                             version: sdl.version())
+  endif
   sdl_image = dependency('SDL2_image', required: get_option('sdl_image'),
                          method: 'pkg-config')
 else
-- 
2.31.1