Temporary header file '/tmp/oOVo9c1VUc/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
#ifdef __cplusplus
// C17 compat layer
#define _Alignof(type) alignof(type)
#endif
#define getaddrinfo_a(a,b,c,d)

  // add includes
  #include "/usr/include/plymouth-1/ply/ply-bitarray.h"
  #include "/usr/include/plymouth-1/ply/ply-buffer.h"
  #include "/usr/include/plymouth-1/ply/ply-command-parser.h"
  #include "/usr/include/plymouth-1/ply/ply-event-loop.h"
  #include "/usr/include/plymouth-1/ply/ply-hashtable.h"
  #include "/usr/include/plymouth-1/ply/ply-i18n.h"
  #include "/usr/include/plymouth-1/ply/ply-key-file.h"
  #include "/usr/include/plymouth-1/ply/ply-list.h"
  #include "/usr/include/plymouth-1/ply/ply-logger.h"
  #include "/usr/include/plymouth-1/ply/ply-progress.h"
  #include "/usr/include/plymouth-1/ply/ply-rectangle.h"
  #include "/usr/include/plymouth-1/ply/ply-region.h"
  #include "/usr/include/plymouth-1/ply/ply-terminal-session.h"
  #include "/usr/include/plymouth-1/ply/ply-trigger.h"
  #include "/usr/include/plymouth-1/ply/ply-utils.h"
  #include "/usr/include/plymouth-1/ply-boot-client/ply-boot-client.h"
  #include "/usr/include/plymouth-1/ply-boot-client/ply-boot-protocol.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-boot-splash-plugin.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-boot-splash.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-device-manager.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-keyboard.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-pixel-buffer.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-pixel-display.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-renderer-plugin.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-renderer.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-terminal.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-text-display.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-text-progress-bar.h"
  #include "/usr/include/plymouth-1/ply-splash-core/ply-text-step-bar.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-animation.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-capslock-icon.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-entry.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-image.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-keymap-icon.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-keymap-metadata.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-label-plugin.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-label.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-progress-animation.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-progress-bar.h"
  #include "/usr/include/plymouth-1/ply-splash-graphics/ply-throbber.h"

  // add classes
  _ply_rectangle* tmp_add_class_0;
  ucontext_t* tmp_add_class_1;

The GCC parameters:
  gcc -fdump-lang-raw -fkeep-inline-functions -c -x c++ -fpermissive -w "/tmp/oOVo9c1VUc/dump1.h"  -I/usr/include/plymouth-1/ply-splash-core -I/usr/include/plymouth-1/ply