pngfix: del workround for GCC7.1 -Wstrict-overflow
Previously pngfix had been made warning-free in GCC7.1 by marking auto
variables (volatile). This prevented the arithmetic optimizations which
caused warnings from GCC7.1 with higher values -Wstrict-overflow=<n>
GCC has moved on a lot since 7.1 and pngfix.c now compiles with just one
warning using -Wstrict-overflow=5. The change includes a change to make
this go away by performing the rearrangement GCC was using in the code:
i == ndigits-1
becomes:
i+1 == ndigits
i is initialized to ndigits and has been decremented at least once so
this is fine.
Test, configure:
CFLAGS="-Wall -Wextra -Wno-maybe-uninitialized -Wstrict-overflow=5" \
../configure --enable-werror
make
make cehck
Test, cmake:
cmake ..
make
make test
Signed-off-by: John Bowler <jbowler@acm.org>
diff --git a/contrib/tools/pngfix.c b/contrib/tools/pngfix.c
index 0dd0dbb..025e687 100644
--- a/contrib/tools/pngfix.c
+++ b/contrib/tools/pngfix.c
@@ -1,6 +1,6 @@
/* pngfix.c
*
- * Copyright (c) 2014-2017 John Cunningham Bowler
+ * Copyright (c) 2014-2017,2024 John Cunningham Bowler
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
@@ -20,19 +20,6 @@
#define implies(x,y) assert(!(x) || (y))
-#ifdef __GNUC__
- /* This is used to fix the error:
- *
- * pngfix.c:
- * In function 'zlib_advance':
- * pngfix.c:181:13: error: assuming signed overflow does not
- * occur when simplifying conditional to constant [-Werror=strict-overflow]
- */
-# define FIX_GCC volatile
-#else
-# define FIX_GCC
-#endif
-
#define PROGRAM_NAME "pngfix"
/* Define the following to use this program against your installed libpng,
@@ -218,7 +205,7 @@
* in_digits+1 if add is known to be in the range -65535..65535.
*/
{
- FIX_GCC int out_digits = 0;
+ int out_digits = 0;
while (out_digits < in_digits)
{
@@ -263,7 +250,7 @@
}
static int
-uarb_mult_digit(uarb acc, int a_digits, uarb num, FIX_GCC int n_digits,
+uarb_mult_digit(uarb acc, int a_digits, uarb num, int n_digits,
png_uint_16 val)
/* Primitive one-digit multiply - 'val' must be 0..65535. Note that this
* primitive is a multiply and accumulate - the result of *num * val is added
@@ -336,7 +323,7 @@
* 1..15
*/
{
- FIX_GCC int i = ndigits;
+ int i = ndigits;
png_uint_16 carry = 0;
assert(right_shift >= 1 && right_shift <= 15);
@@ -351,7 +338,7 @@
inout[i] = temp;
/* The shift may reduce ndigits */
- if (i == ndigits-1 && temp == 0)
+ if (i+1 == ndigits && temp == 0)
ndigits = i;
}
