Improve GC+Cairo workaround

Suggested by Eli Zaretskii (Bug#20890#31).
* src/font.h (font_data_structures_may_be_ill_formed): New function.
* src/ftfont.c (ftfont_close):
* src/ftcrfont.c (ftcrfont_close): Use it.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/font.h b/src/font.h
index d88c8eb4f66..469431fee67 100644
--- a/src/font.h
+++ b/src/font.h
@@ -945,6 +945,22 @@ extern void font_deferred_log (const char *, Lisp_Object, Lisp_Object);
       font_deferred_log ((ACTION), (ARG), (RESULT));    \
   } while (false)
 
+/* FIXME: This is for use in functions that can be called while
+   garbage-collecting, but which assume that Lisp data structures are
+   properly-formed.  This invalid assumption can lead to core dumps
+   (Bug#20890).  */
+INLINE bool
+font_data_structures_may_be_ill_formed (void)
+{
+#ifdef USE_CAIRO
+  /* Although this works around Bug#20890, it is probably not the
+     right thing to do.  */
+  return gc_in_progress;
+#else
+  return false;
+#endif
+}
+
 INLINE_HEADER_END
 
 #endif  /* not EMACS_FONT_H */