Temporary header file '/tmp/2I23bhEw_Z/dump1.h' with the following content will be compiled to create GCC translation unit dump:

  // add defines
  #define __STDC_VERSION__ 201710L
#define _GXX_NULLPTR_T
#define CLUTTER_ENABLE_COMPOSITOR_API 1
#define _REGEX_NELTS(n)
#define _Atomic
#define PACKED
#define getaddrinfo_a(a,b,c,d)

  // add includes
  #include "/usr/include/alleggl.h"
  #include "/usr/include/allegrogl/GLext/gl_ext_alias.h"
  #include "/usr/include/allegrogl/GLext/gl_ext_api.h"
  #include "/usr/include/allegrogl/GLext/gl_ext_defs.h"
  #include "/usr/include/allegrogl/GLext/gl_ext_list.h"
  #include "/usr/include/allegrogl/GLext/glx_ext_alias.h"
  #include "/usr/include/allegrogl/GLext/glx_ext_api.h"
  #include "/usr/include/allegrogl/GLext/glx_ext_defs.h"
  #include "/usr/include/allegrogl/GLext/glx_ext_list.h"
  #include "/usr/include/allegrogl/GLext/wgl_ext_alias.h"
  #include "/usr/include/allegrogl/GLext/wgl_ext_api.h"
  #include "/usr/include/allegrogl/GLext/wgl_ext_defs.h"
  #include "/usr/include/allegrogl/GLext/wgl_ext_list.h"
  #include "/usr/include/allegrogl/alleggl_config.h"
  #include "/usr/include/allegrogl/gl_ext.h"
  #include "/usr/include/allegrogl/gl_header_detect.h"

The GCC parameters:
  gcc -fdump-lang-raw -fkeep-inline-functions -c -x c++ -fpermissive -w "/tmp/2I23bhEw_Z/dump1.h"

In file included from /tmp/2I23bhEw_Z/dump1.h:12:
/usr/include/alleggl.h:68:10: fatal error: GL/gl.h: No such file or directory
   68 | #include <GL/gl.h>
      |          ^~~~~~~~~
compilation terminated.