IMPROVES-i5 full fix on sequal_full()

lib11sht.h

@@ -9,7 +9,9 @@
 #ifndef LIB11SHT_H
 #define LIB11SHT_H
 
-#define LEVN_SBUFF 256  /* min size for s1/s2 buffers and bounded input */
+#include <stddef.h>  /* size_t */
+
+#define LEVN_SBUFF 256  /* recommended size for s1/s2 buffers */
 
 /* Compare similarity between two strings (after asciify + trim + lowercase).
  * Symmetric in shape with fequal(a, b, delta).
@@ -31,11 +33,14 @@ int sequal(char *a, char *b, float shold);
  * (e.g. cmp11sht CLI's -o / -n flags).
  *
  * Extra parameters:
- *   ratio   out: Levenshtein similarity 0.0..1.0 (1.0 on exact-after-normalize)
- *   s1, s2  out: caller-provided buffers (>= LEVN_SBUFF) filled with the
- *           normalized inputs
+ *   ratio    out: Levenshtein similarity 0.0..1.0 (1.0 on exact-after-normalize)
+ *   s1, s2   out: caller-provided buffers filled with the normalized inputs
+ *   s1_size  size of s1 in bytes (writes capped at s1_size-1 + final NUL)
+ *   s2_size  size of s2 in bytes (writes capped at s2_size-1 + final NUL)
  */
-int sequal_full(char *a, char *b, float shold, float *ratio, char *s1, char *s2);
+int sequal_full(char *a, char *b, float shold, float *ratio,
+                char *s1, size_t s1_size,
+                char *s2, size_t s2_size);
 
 /* Compare two floats within ±delta.
  * Returns: