[Mesa-dev] [PATCH 3/4] configure: Fix egl compilation without x11 headers

[Benjamin Franzke]

2012/3/1 Chad Versace <chad.versace at linux.intel.com>:
> On 03/01/2012 11:39 AM, Benjamin Franzke wrote:
>> 2012/3/1 Chad Versace <chad.versace at linux.intel.com>:
>>> On 02/29/2012 07:36 AM, Benjamin Franzke wrote:
>>>> We dont want eglplatform.h to typedef egl native types
>>>> to x11 types, when x11 headers are not available.
>>>> ---
>>>>  configure.ac |    4 ++++
>>>>  1 files changed, 4 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/configure.ac b/configure.ac
>>>> index 0caa1b1..92a0e52 100644
>>>> --- a/configure.ac
>>>> +++ b/configure.ac
>>>> @@ -1402,6 +1402,10 @@ if test "x$enable_egl" = xyes; then
>>>>
>>>>      AC_CHECK_FUNC(mincore, [DEFINES="$DEFINES -DHAVE_MINCORE"])
>>>>
>>>> +    if test "$have_x" != yes; then
>>>> +        DEFINES="$DEFINES -DMESA_EGL_NO_X11_HEADERS"
>>>> +    fi
>>>> +
>>>>      if test "$enable_static" != yes; then
>>>>          # build egl_glx when libGL is built
>>>>          if test "x$enable_glx" = xyes; then
>>>
>>> After examining the where the macro is used, in eglplatform.h ...
>>>
>>> --- snip ---
>>> #elif defined(__unix__)
>>>
>>> #ifdef MESA_EGL_NO_X11_HEADERS
>>>
>>> typedef void            *EGLNativeDisplayType;
>>> typedef khronos_uint32_t EGLNativePixmapType;
>>> typedef khronos_uint32_t EGLNativeWindowType;
>>>
>>> #else
>>>
>>> /* X11 (tentative)  */
>>> #include <X11/Xlib.h>
>>> #include <X11/Xutil.h>
>>>
>>> typedef Display *EGLNativeDisplayType;
>>> typedef Pixmap   EGLNativePixmapType;
>>> typedef Window   EGLNativeWindowType;
>>>
>>> #endif /* MESA_EGL_NO_X11_HEADERS */
>>> --- end snip ---
>>>
>>> I can't think of a valid reason for the #else branch to ever be taken.
>>> If you're building EGL on Unix/Linux, but not for gbm (__GBM__), Android (ANDRDOID),
>>> Wayland (WL_EGL_PLATFORM), or X (the default), then for what platform
>>> are you building libEGL? (The question is not rhetorical).
>>
>> The platform headers for wayland/gbm are not included when compiling
>> src/egl/main/* or some other common code in st/egl, that is when the
>> else branch is taken.
>> So currently we include Xlib.h when building without x11 platform,
>> that fails if its not available.
>> Will add a note to the commit message.
>
> It appears that the patch may introduce a bug in the 64-bit build of libEGL,
> but I'm not certain. Here's my reasoning.
>
> 1. Suppose that
>   - This patch is applied.
>   - The system has no X headers installed.
>   - Some Wayland application has a source file, broken.c, that
>     #includes <wayland-egl.h> then <EGL/egl.h>.
>
> 2. In eglapi.c, which defines eglCreateWindowSurface, EGLNativeWindowType
>   will be defined as khronos_uint32_t.
>
> 3. In broken.c, wayland-egl.h first defines WL_EGL_PLATFORM. Then
>   EGLNativeWindowType will be defined as wl_egl_window*, a 64-bit type.

Yes, thanks for pointing that out.
We should just typedef them to khronos_uintptr_t instead.

>
> Without the patch, eglapi.c safely typedefs EGLNativeWindowType to XID, which matches
> the system's pointer size.
>
> - Chad
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