After commit 45eb3bfd32 (device-select: only try wayland/x11 if the
required vars are set, 2024-10-18), building `device_select_layer.c` can
results in compiler errors on some stricter build configurations
(-Werror,-Wunused-variable):
-----------------------------------------------------------------------
../src/vulkan/device-select-layer/device_select_layer.c:149:9: error: unused variable 'has_wayland' [-Werror,-Wunused-variable]
149 | bool has_wayland = getenv("WAYLAND_DISPLAY") || getenv("WAYLAND_SOCKET");
| ^~~~~~~~~~~
../src/vulkan/device-select-layer/device_select_layer.c:150:9: error: unused variable 'has_xcb' [-Werror,-Wunused-variable]
150 | bool has_xcb = !!getenv("DISPLAY");
| ^~~~~~~
2 errors generated.
-----------------------------------------------------------------------
So guard the declarations of the `has_wayland` and `has_xcb` variables
behind `VK_USE_PLATFORM_WAYLAND_KHR` and `VK_USE_PLATFORM_XCB_KHR`
respectively, just like the user code.
Note: the declarations are still kept outside of the loop body, in order
to assign the variables once and for all.
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37571>
Antonio Ospite
613bfe0b8b