* coding.c (DECODE_COMPOSITION_RULE): If the rule is invalid, goto invalid_code

directly, rather than having caller test rule sign.  This avoids
some unnecessary tests.
* composite.h (COMPOSITION_ENCODE_RULE_VALID): New macro.
(COMPOSITION_ENCODE_RULE): Arguments now must be valid.  This
affects only one use, in DECODE_COMPOSITION_RULE, which is changed.

1 files changed, 5 insertions, 6 deletions

diff --git a/src/coding.c b/src/coding.c
index 6e5d0655258..555c29cbdf3 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -3254,13 +3254,13 @@ detect_coding_iso_2022 (struct coding_system *coding,
 
 /* Decode a composition rule C1 and maybe one more byte from the
    source, and set RULE to the encoded composition rule.  If the rule
-   is invalid, set RULE to some negative value.  */
+   is invalid, goto invalid_code.  */
 
 #define DECODE_COMPOSITION_RULE(rule)                                   \
   do {                                                                  \
     rule = c1 - 32;                                                     \
     if (rule < 0)                                                       \
-      break;                                                            \
+      goto invalid_code;                                                \
     if (rule < 81)              /* old format (before ver.21) */        \
       {                                                                 \
         int gref = (rule) / 9;                                          \
@@ -3274,9 +3274,10 @@ detect_coding_iso_2022 (struct coding_system *coding,
         int b;                                                          \
                                                                         \
         ONE_MORE_BYTE (b);                                              \
+        if (! COMPOSITION_ENCODE_RULE_VALID (rule - 81, b - 32))        \
+          goto invalid_code;                                            \
         rule = COMPOSITION_ENCODE_RULE (rule - 81, b - 32);             \
-        if (rule >= 0)                                                  \
-          rule += 0x100;   /* to destinguish it from the old format */  \
+        rule += 0x100;   /* Distinguish it from the old format.  */     \
       }                                                                 \
   } while (0)
 
@@ -3543,8 +3544,6 @@ decode_coding_iso_2022 (struct coding_system *coding)
           int rule;
 
           DECODE_COMPOSITION_RULE (rule);
-          if (rule < 0)
-            goto invalid_code;
           STORE_COMPOSITION_RULE (rule);
           continue;
         }