catch one more case in umult64 (Tomi Jylhä-Ollila)

CHANGES

@@ -2,6 +2,7 @@
   add fmt_strm
   add iob_addbuf_munmap
   add socket_deferaccept
+  catch one more case in umult64 (Tomi Jylhä-Ollila)
 
 0.26:
   fix really pathological case where io_timeouted would never

mult/umult64.c

@@ -37,7 +37,11 @@ int umult64(uint64 a,uint64 b,uint64* c) {
 
   a=(uint64)(ahi)*blo+(uint64)(alo)*bhi;
   if (a>0xffffffff) return 0;
-  *c=(a<<32)+(uint64)(alo)*blo;
+  {
+    uint64 x=(uint64)(alo)*blo;
+    if (x+(a<<32) < x) return 0;
+    *c=x+(a<<32);
+  }
   return 1;
 }
 

test/mult.c

@@ -19,5 +19,7 @@ int main() {
   assert(imult64(-0x4000000000000000ll,2,&c)==1 && c==(int64)-0x8000000000000000ll);
   assert(imult64(0x3fffffffffffffffll,2,&c)==1 && c==0x7ffffffffffffffell);
 
+  assert(umult64(0x0000000100000002ull,0x00000000ffffffffull,&c)==0);
+
   return 0;
 }

va_narg.h

@@ -30,4 +30,7 @@
          19,18,17,16,15,14,13,12,11,10, \
          9,8,7,6,5,4,3,2,1,0
 
+#define COUNT(x, ...)  ({ typeof (x) __fnord[] = { x, __VA_ARGS__ }; sizeof(__fnord)/sizeof(__fnord[0]); })
+#define COUNT_PREFIX(x, ...)  ({ typeof (x) __fnord[] = { x, __VA_ARGS__ }; sizeof(__fnord)/sizeof(__fnord[0]); }), x, __VA_ARGS__
+
 #endif