Make sure cairo_int_status_t values fit in int8_t

It was reported by Liu Yubao that cairo_status_t may be chosen to be
an int8_t by the compiler, in that case cairo_int_status_t values
assigned to cairo_status_t would overflow.  Fix this by allocating
the values in int8_t range, and add compile-time sanity checks.

1 files changed, 8 insertions, 5 deletions

diff --git a/src/cairo-types-private.h b/src/cairo-types-private.h
index 0b66df28..36661e48 100644
--- a/src/cairo-types-private.h
+++ b/src/cairo-types-private.h
@@ -130,16 +130,19 @@ typedef enum _cairo_paginated_mode {
 } cairo_paginated_mode_t;
 
 /* Sure wish C had a real enum type so that this would be distinct
- * from #cairo_status_t. Oh well, without that, I'll use this bogus 1000
- * offset */
+ * from #cairo_status_t. Oh well, without that, I'll use this bogus 100
+ * offset.  We want to keep it fit in int8_t as the compiler may choose
+ * that for cairo_status_t */
 typedef enum _cairo_int_status {
-    CAIRO_INT_STATUS_DEGENERATE = 1000,
-    CAIRO_INT_STATUS_UNSUPPORTED,
+    CAIRO_INT_STATUS_UNSUPPORTED = 100,
+    CAIRO_INT_STATUS_DEGENERATE,
     CAIRO_INT_STATUS_NOTHING_TO_DO,
     CAIRO_INT_STATUS_CACHE_EMPTY,
     CAIRO_INT_STATUS_FLATTEN_TRANSPARENCY,
     CAIRO_INT_STATUS_IMAGE_FALLBACK,
-    CAIRO_INT_STATUS_ANALYZE_META_SURFACE_PATTERN
+    CAIRO_INT_STATUS_ANALYZE_META_SURFACE_PATTERN,
+
+    CAIRO_INT_STATUS_LAST_STATUS
 } cairo_int_status_t;
 
 typedef enum _cairo_internal_surface_type {