It turns out that sys/hash.h also uses Chris Toreks hash algorithm
in the same 1:1 way that was present in Berkeley DB a decade ago.
So maybe "i prefer leaving optimization up to the compiler" should
be applied here, too. The patch does this.
And - you know, i never made it into that gcc(1) code jungle, but
maybe someone with experience simply needs to toggle a switch for
better behaviour - the following seems strange to me:
#include <stdio.h>
int main(void) {
int i = 3;
printf("i = %d\n", i);
#ifdef T1
for (int x = 1; x < i; ++x)
#else
int x = 1;
#endif
printf("x = %d\n", x);
return 0;
}
?0%1[steffen@obsd tmp]$ /usr/bin/gcc -W -Wall -pedantic -o t -c t.c
t.c: In function 'main':
t.c:9: warning: ISO C90 forbids mixed declarations and code
?0%1[steffen@obsd tmp]$ /usr/bin/gcc -DT1 -W -Wall -pedantic -o t -c t.c
t.c: In function 'main':
t.c:7: error: 'for' loop initial declaration used outside C99 mode
?1%1[steffen@obsd tmp]$
E.g., clang(1) does this (also for -std=c90):
?0%0[steffen@sherwood tmp]$ clang -DT1 -W -Wall -pedantic -ansi -o t -c t.c
t.c:7:14: warning: variable declaration in for loop is a C99-specific
feature [-pedantic]
for (int x = 1; x < i; ++x)
^
1 warning generated.
?0%0[steffen@sherwood tmp]$ clang -W -Wall -pedantic -ansi -o t -c t.c
t.c:9:13: warning: ISO C90 forbids mixing declarations and code
[-Wdeclaration-after-statement]
int x = 1;
^
1 warning generated.
?0%0[steffen@sherwood tmp]$
--steffen
Index: sys/sys/hash.h
===================================================================
RCS file: /Users/steffen/arena/code.openbsd/src/sys/sys/hash.h,v
retrieving revision 1.5
diff -a -p -u -r1.5 hash.h
--- sys/sys/hash.h 24 Sep 2010 13:24:53 -0000 1.5
+++ sys/sys/hash.h 14 Feb 2012 17:05:43 -0000
@@ -40,7 +40,7 @@
/* Convenience */
#ifndef HASHINIT
#define HASHINIT 5381
-#define HASHSTEP(x,c) (((x << 5) + x) + (c))
+#define HASHSTEP(x,c) ((x)*33 + (c))
#endif
/*
