shared: rewrite fail_on_null() as abort_oom_if_null()

Recently I learnt that fprintf() is not async-signal-safe. Maybe it also
attempts to allocate memory sometimes. Hence, using it when we
presumably are out of memory is wishful thinking.

Therefore replace that with async-signal-safe code. If you have to check
pointers from traditional signal handlers, now you could do that too!

While doing this, we also lose the string formatting for line number. I
would argue that printing file and line number is not that useful, if
the system really is out of memory. If not out of memory, a core dump
would give us much more detailed information about what went wrong.

clients/window.c had some calls to fail_on_null() and these are simply
replaced. They were used for checking that creating new wl_proxy by
issuing a protocol request worked, and IIRC that only fails on
out-of-memory, so the same rationale applies here.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.com>

clients/window.c

@@ -5081,14 +5081,14 @@ window_create(struct display *display)
 		window->xdg_surface =
 			xdg_wm_base_get_xdg_surface(window->display->xdg_shell,
 						    window->main_surface->surface);
-		fail_on_null(window->xdg_surface, 0, __FILE__, __LINE__);
+		abort_oom_if_null(window->xdg_surface);
 
 		xdg_surface_add_listener(window->xdg_surface,
 					 &xdg_surface_listener, window);
 
 		window->xdg_toplevel =
 			xdg_surface_get_toplevel(window->xdg_surface);
-		fail_on_null(window->xdg_toplevel, 0, __FILE__, __LINE__);
+		abort_oom_if_null(window->xdg_toplevel);
 
 		xdg_toplevel_add_listener(window->xdg_toplevel,
 					  &xdg_toplevel_listener, window);
@@ -5293,7 +5293,7 @@ create_menu(struct display *display,
 	menu->widget = window_add_widget(menu->window, menu);
 	menu->frame = frame_create(window->display->theme, 0, 0,
 	                           FRAME_BUTTON_NONE, NULL, NULL);
-	fail_on_null(menu->frame, 0, __FILE__, __LINE__);
+	abort_oom_if_null(menu->frame);
 	menu->entries = entries;
 	menu->count = count;
 	menu->release_count = 0;
@@ -5327,7 +5327,7 @@ create_simple_positioner(struct display *display,
 	struct xdg_positioner *positioner;
 
 	positioner = xdg_wm_base_create_positioner(display->xdg_shell);
-	fail_on_null(positioner, 0, __FILE__, __LINE__);
+	abort_oom_if_null(positioner);
 	xdg_positioner_set_anchor_rect(positioner, x, y, 1, 1);
 	xdg_positioner_set_size(positioner, w, h);
 	xdg_positioner_set_anchor(positioner,
@@ -5372,7 +5372,7 @@ window_show_menu(struct display *display,
 	window->xdg_surface =
 		xdg_wm_base_get_xdg_surface(display->xdg_shell,
 					    window->main_surface->surface);
-	fail_on_null(window->xdg_surface, 0, __FILE__, __LINE__);
+	abort_oom_if_null(window->xdg_surface);
 
 	xdg_surface_add_listener(window->xdg_surface,
 				 &xdg_surface_listener, window);
@@ -5385,7 +5385,7 @@ window_show_menu(struct display *display,
 	window->xdg_popup = xdg_surface_get_popup(window->xdg_surface,
 						  parent->xdg_surface,
 						  positioner);
-	fail_on_null(window->xdg_popup, 0, __FILE__, __LINE__);
+	abort_oom_if_null(window->xdg_popup);
 	xdg_positioner_destroy(positioner);
 	xdg_popup_grab(window->xdg_popup, input->seat,
 		       display_get_serial(window->display));

shared/xalloc.h

@@ -1,5 +1,6 @@
 /*
  * Copyright © 2008 Kristian Høgsberg
+ * Copyright 2022 Collabora, Ltd.
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files (the
@@ -31,35 +32,32 @@ extern "C" {
 #endif
 
 #include <errno.h>
-#include <stdint.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <string.h>
 
 #include <libweston/zalloc.h>
 
-
 static inline void *
-fail_on_null(void *p, size_t size, char *file, int32_t line)
+abort_oom_if_null(void *p)
 {
-	if (p == NULL) {
-		fprintf(stderr, "[%s] ", program_invocation_short_name);
-		if (file)
-			fprintf(stderr, "%s:%d: ", file, line);
-		fprintf(stderr, "out of memory");
-		if (size)
-			fprintf(stderr, " (%zd)", size);
-		fprintf(stderr, "\n");
-		exit(EXIT_FAILURE);
-	}
+	static const char oommsg[] = ": out of memory\n";
+
+	if (p)
+		return p;
+
+	write(STDERR_FILENO, program_invocation_short_name,
+	      strlen(program_invocation_short_name));
+	write(STDERR_FILENO, oommsg, strlen(oommsg));
 
-	return p;
+	abort();
 }
 
-#define xmalloc(s) (fail_on_null(malloc(s), (s), __FILE__, __LINE__))
-#define xzalloc(s) (fail_on_null(zalloc(s), (s), __FILE__, __LINE__))
-#define xcalloc(n, s) (fail_on_null(calloc(n, s), (n) * (s), __FILE__, __LINE__))
-#define xstrdup(s) (fail_on_null(strdup(s), 0, __FILE__, __LINE__))
-#define xrealloc(p, s) (fail_on_null(realloc(p, s), (s), __FILE__, __LINE__))
+#define xmalloc(s) (abort_oom_if_null(malloc(s)))
+#define xzalloc(s) (abort_oom_if_null(zalloc(s)))
+#define xcalloc(n, s) (abort_oom_if_null(calloc(n, s)))
+#define xstrdup(s) (abort_oom_if_null(strdup(s)))
+#define xrealloc(p, s) (abort_oom_if_null(realloc(p, s)))
 
 #ifdef  __cplusplus
 }