Avoid shift equal to bits in type (caused endless loop).
Also clean up comparisons between different types, and some odd
indentation problems that showed up somehow.
A new endless loop was introduced by the clang compiler, which
apparently does odd things when the right operand of << is equal to
or greater than the number of bits in the type. The C standard in
fact states that the behavior of << is undefined in that case. The
loop was rewritten to use single-bit shifts.
diff --git a/examples/enough.c b/examples/enough.c
index c40410b..b991144 100644
--- a/examples/enough.c
+++ b/examples/enough.c
@@ -1,7 +1,7 @@
/* enough.c -- determine the maximum size of inflate's Huffman code tables over
* all possible valid and complete Huffman codes, subject to a length limit.
- * Copyright (C) 2007, 2008 Mark Adler
- * Version 1.3 17 February 2008 Mark Adler
+ * Copyright (C) 2007, 2008, 2012 Mark Adler
+ * Version 1.4 18 August 2012 Mark Adler
*/
/* Version history:
@@ -14,6 +14,9 @@
1.3 17 Feb 2008 Add argument for initial root table size
Fix bug for initial root table size == max - 1
Use a macro to compute the history index
+ 1.4 18 Aug 2012 Avoid shifts more than bits in type (caused endless loop!)
+ Clean up comparisons of different types
+ Clean up code indentation
*/
/*
@@ -236,8 +239,8 @@
for (use = least; use <= most; use++) {
got = count(syms - use, len + 1, (left - use) << 1);
sum += got;
- if (got == -1 || sum < got) /* overflow */
- return -1;
+ if (got == (big_t)0 - 1 || sum < got) /* overflow */
+ return (big_t)0 - 1;
}
/* verify that all recursive calls are productive */
@@ -458,6 +461,7 @@
int n; /* number of symbols to code for this run */
big_t got; /* return value of count() */
big_t sum; /* accumulated number of codes over n */
+ code_t word; /* for counting bits in code_t */
/* set up globals for cleanup() */
code = NULL;
@@ -466,19 +470,19 @@
/* get arguments -- default to the deflate literal/length code */
syms = 286;
- root = 9;
+ root = 9;
max = 15;
if (argc > 1) {
syms = atoi(argv[1]);
if (argc > 2) {
root = atoi(argv[2]);
- if (argc > 3)
- max = atoi(argv[3]);
- }
+ if (argc > 3)
+ max = atoi(argv[3]);
+ }
}
if (argc > 4 || syms < 2 || root < 1 || max < 1) {
fputs("invalid arguments, need: [sym >= 2 [root >= 1 [max >= 1]]]\n",
- stderr);
+ stderr);
return 1;
}
@@ -487,18 +491,17 @@
max = syms - 1;
/* determine the number of bits in a code_t */
- n = 0;
- while (((code_t)1 << n) != 0)
- n++;
+ for (n = 0, word = 1; word; n++, word <<= 1)
+ ;
/* make sure that the calculation of most will not overflow */
- if (max > n || syms - 2 >= (((code_t)0 - 1) >> (max - 1))) {
+ if (max > n || (code_t)(syms - 2) >= (((code_t)0 - 1) >> (max - 1))) {
fputs("abort: code length too long for internal types\n", stderr);
return 1;
}
/* reject impossible code requests */
- if (syms - 1 > ((code_t)1 << max) - 1) {
+ if ((code_t)(syms - 1) > ((code_t)1 << max) - 1) {
fprintf(stderr, "%d symbols cannot be coded in %d bits\n",
syms, max);
return 1;
@@ -532,7 +535,7 @@
for (n = 2; n <= syms; n++) {
got = count(n, 1, 2);
sum += got;
- if (got == -1 || sum < got) { /* overflow */
+ if (got == (big_t)0 - 1 || sum < got) { /* overflow */
fputs("abort: can't count that high!\n", stderr);
cleanup();
return 1;
@@ -556,9 +559,9 @@
}
/* find and show maximum inflate table usage */
- if (root > max) /* reduce root to max length */
- root = max;
- if (syms < ((code_t)1 << (root + 1)))
+ if (root > max) /* reduce root to max length */
+ root = max;
+ if ((code_t)syms < ((code_t)1 << (root + 1)))
enough(syms);
else
puts("cannot handle minimum code lengths > root");
