fix signed range problems with hex conversions

Make hexval_table[] "const".  Also make sure that the accessor
function hexval() does not access the table with out-of-range
values by declaring its parameter "unsigned char", instead of
"unsigned int".

With this, gcc can just generate:

	movzbl  (%rdi), %eax
	movsbl  hexval_table(%rax),%edx
	movzbl  1(%rdi), %eax
	movsbl  hexval_table(%rax),%eax
	sall    $4, %edx
	orl     %eax, %edx

for the code to generate a byte from two hex characters.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/cache.h b/cache.h
index 7cedda684f81e5b7bc111c2322ef1f4b2fc97d90..bea8cad5b2b1f81199153f1755e81113b963655b 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -302,8 +302,8 @@ extern int legacy_loose_object(unsigned char *);
 extern int has_pack_file(const unsigned char *sha1);
 extern int has_pack_index(const unsigned char *sha1);
 
-extern signed char hexval_table[256];
-static inline unsigned int hexval(unsigned int c)
+extern const signed char hexval_table[256];
+static inline unsigned int hexval(unsigned char c)
 {
        return hexval_table[c];
 }

diff --git a/sha1_file.c b/sha1_file.c
index 523417027a1785d4ab5b729d03ba794efc1bb4d4..ae9bd1fc2f9eca19b9708fef876faff16fd917fe 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -32,7 +32,7 @@ const unsigned char null_sha1[20];
 
 static unsigned int sha1_file_open_flag = O_NOATIME;
 
-signed char hexval_table[256] = {
+const signed char hexval_table[256] = {
         -1, -1, -1, -1, -1, -1, -1, -1,                /* 00-07 */
         -1, -1, -1, -1, -1, -1, -1, -1,                /* 08-0f */
         -1, -1, -1, -1, -1, -1, -1, -1,                /* 10-17 */