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test: add configuration tests and fix bugs

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The two new configuation tests, fixed.dfa and float-fixed.dfa verify
that the 'standard' configuration of libpng works without floating point
arithmetic.

Signed-off-by: John Bowler <jbowler@acm.org>
This commit is contained in:
John Bowler 2025-01-27 10:51:01 -08:00
parent a8242dd947
commit c4b20d0a3a
3 changed files with 53 additions and 0 deletions
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15
contrib/conftest/fixed.dfa Normal file
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@ -0,0 +1,15 @@
# fixed.dfa
# Build time configuration of libpng
#
# Author: John Bowler
# Copyright: (c) John Bowler, 2025
# Usage rights:
# To the extent possible under law, the author has waived all copyright and
# related or neighboring rights to this work. This work is published from:
# United States.
#
# Test the standard libpng configuration without floating point (the internal
# fixed point implementations are used instead).
#
option FLOATING_ARITHMETIC off
option FLOATING_POINT off

14
contrib/conftest/float-fixed.dfa Normal file
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# fixed-float.dfa
# Build time configuration of libpng
#
# Author: John Bowler
# Copyright: (c) John Bowler, 2025
# Usage rights:
# To the extent possible under law, the author has waived all copyright and
# related or neighboring rights to this work. This work is published from:
# United States.
#
# Test the standard libpng configuration with the fixed point internal
# implementation in place of the default floating point
#
option FLOATING_ARITHMETIC off

24
png.c
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@ -2931,6 +2931,30 @@ png_gamma_significant(png_fixed_point gamma_val)
gamma_val > PNG_FP_1 + PNG_GAMMA_THRESHOLD_FIXED;
}
#ifndef PNG_FLOATING_ARITHMETIC_SUPPORTED
/* A local convenience routine. */
static png_fixed_point
png_product2(png_fixed_point a, png_fixed_point b)
{
/* The required result is a * b; the following preserves accuracy. */
#ifdef PNG_FLOATING_ARITHMETIC_SUPPORTED /* Should now be unused */
double r = a * 1E-5;
r *= b;
r = floor(r+.5);
if (r <= 2147483647. && r >= -2147483648.)
return (png_fixed_point)r;
#else
png_fixed_point res;
if (png_muldiv(&res, a, b, 100000) != 0)
return res;
#endif
return 0; /* overflow */
}
#endif /* FLOATING_ARITHMETIC */
png_fixed_point
png_reciprocal2(png_fixed_point a, png_fixed_point b)
{