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fix: Restore the build for strictly-conforming standard compilers
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In libpng version 1.6.45 we inadvertently used a declaration after
a statement, which works for compilers supporting C99 and newer,
but fails with C89 compilers, which we are still supporting in the
branch 'libpng16'.

Moreover, in commit 92e8581, we used
the macro `PNG_FIXED_EXPORT` in a manner that introduced a spurious ';'
character, which broke the build for all standard-conforming compilers.

Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
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@jbowler @ctruta
jbowler authored and ctruta committed Jan 21, 2025
1 parent 19a5a5e commit 4d7c993
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93 changes: 48 additions & 45 deletions png.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1544,56 +1544,59 @@ png_XYZ_from_xy(png_XYZ *XYZ, const png_xy *xy)
* Adobe Wide Gamut RGB
* 0.258728243040113 0.724682314948566 0.016589442011321
*/
int error = 0;

/* By the argument above overflow should be impossible here, however the
* code now simply returns a failure code. The xy subtracts in the arguments
* to png_muldiv are *not* checked for overflow because the checks at the
* start guarantee they are in the range 0..110000 and png_fixed_point is a
* 32-bit signed number.
*/
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 8) == 0)
return 1;
denominator = png_fp_sub(left, right, &error);
if (error) return 1;
{
int error = 0;

/* Now find the red numerator. */
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 8) == 0)
return 1;
/* By the argument above overflow should be impossible here, however the
* code now simply returns a failure code. The xy subtracts in the
* arguments to png_muldiv are *not* checked for overflow because the
* checks at the start guarantee they are in the range 0..110000 and
* png_fixed_point is a 32-bit signed number.
*/
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->redy - xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->redx - xy->bluex, 8) ==
0)
return 1;
denominator = png_fp_sub(left, right, &error);
if (error) return 1;

/* Overflow is possible here and it indicates an extreme set of PNG cHRM
* chunk values. This calculation actually returns the reciprocal of the
* scale value because this allows us to delay the multiplication of white-y
* into the denominator, which tends to produce a small number.
*/
if (png_muldiv(&red_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
red_inverse <= xy->whitey /* r+g+b scales = white scale */)
return 1;
/* Now find the red numerator. */
if (png_muldiv(&left, xy->greenx-xy->bluex, xy->whitey-xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&right, xy->greeny-xy->bluey, xy->whitex-xy->bluex, 8) ==
0)
return 1;

/* Similarly for green_inverse: */
if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 8) == 0)
return 1;
if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&green_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
green_inverse <= xy->whitey)
return 1;
/* Overflow is possible here and it indicates an extreme set of PNG cHRM
* chunk values. This calculation actually returns the reciprocal of the
* scale value because this allows us to delay the multiplication of
* white-y into the denominator, which tends to produce a small number.
*/
if (png_muldiv(&red_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
red_inverse <= xy->whitey /* r+g+b scales = white scale */)
return 1;

/* And the blue scale, the checks above guarantee this can't overflow but it
* can still produce 0 for extreme cHRM values.
*/
blue_scale = png_fp_sub(png_fp_sub(png_reciprocal(xy->whitey),
png_reciprocal(red_inverse), &error),
png_reciprocal(green_inverse), &error);
if (error || blue_scale <= 0)
return 1;
/* Similarly for green_inverse: */
if (png_muldiv(&left, xy->redy-xy->bluey, xy->whitex-xy->bluex, 8) == 0)
return 1;
if (png_muldiv(&right, xy->redx-xy->bluex, xy->whitey-xy->bluey, 8) == 0)
return 1;
if (png_muldiv(&green_inverse, xy->whitey, denominator,
png_fp_sub(left, right, &error)) == 0 || error ||
green_inverse <= xy->whitey)
return 1;

/* And the blue scale, the checks above guarantee this can't overflow but
* it can still produce 0 for extreme cHRM values.
*/
blue_scale = png_fp_sub(png_fp_sub(png_reciprocal(xy->whitey),
png_reciprocal(red_inverse), &error),
png_reciprocal(green_inverse), &error);
if (error || blue_scale <= 0)
return 1;
}

/* And fill in the png_XYZ. Again the subtracts are safe because of the
* checks on the xy values at the start (the subtracts just calculate the
Expand Down
16 changes: 8 additions & 8 deletions png.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2005,27 +2005,27 @@ PNG_EXPORT(251, void, png_set_cICP, (png_const_structrp png_ptr,
#ifdef PNG_cLLI_SUPPORTED
PNG_FP_EXPORT(252, png_uint_32, png_get_cLLI, (png_const_structrp png_ptr,
png_const_inforp info_ptr, double *maximum_content_light_level,
double *maximum_frame_average_light_level));
double *maximum_frame_average_light_level))
PNG_FIXED_EXPORT(253, png_uint_32, png_get_cLLI_fixed,
(png_const_structrp png_ptr, png_const_inforp info_ptr,
/* The values below are in cd/m2 (nits) and are scaled by 10,000; not
* 100,000 as in the case of png_fixed_point.
*/
png_uint_32p maximum_content_light_level_scaled_by_10000,
png_uint_32p maximum_frame_average_light_level_scaled_by_10000));
png_uint_32p maximum_frame_average_light_level_scaled_by_10000))
#endif

#ifdef PNG_cLLI_SUPPORTED
PNG_FP_EXPORT(254, void, png_set_cLLI, (png_const_structrp png_ptr,
png_inforp info_ptr, double maximum_content_light_level,
double maximum_frame_average_light_level));
double maximum_frame_average_light_level))
PNG_FIXED_EXPORT(255, void, png_set_cLLI_fixed, (png_const_structrp png_ptr,
png_inforp info_ptr,
/* The values below are in cd/m2 (nits) and are scaled by 10,000; not
* 100,000 as in the case of png_fixed_point.
*/
png_uint_32 maximum_content_light_level_scaled_by_10000,
png_uint_32 maximum_frame_average_light_level_scaled_by_10000));
png_uint_32 maximum_frame_average_light_level_scaled_by_10000))
#endif

#ifdef PNG_eXIf_SUPPORTED
Expand Down Expand Up @@ -2083,7 +2083,7 @@ PNG_FP_EXPORT(256, png_uint_32, png_get_mDCV, (png_const_structrp png_ptr,
double *green_x, double *green_y, double *blue_x, double *blue_y,
/* Mastering display luminance in cd/m2 (nits). */
double *mastering_display_maximum_luminance,
double *mastering_display_minimum_luminance));
double *mastering_display_minimum_luminance))

PNG_FIXED_EXPORT(257, png_uint_32, png_get_mDCV_fixed,
(png_const_structrp png_ptr, png_const_inforp info_ptr,
Expand All @@ -2095,7 +2095,7 @@ PNG_FIXED_EXPORT(257, png_uint_32, png_get_mDCV_fixed,
* 10,000.
*/
png_uint_32p mastering_display_maximum_luminance_scaled_by_10000,
png_uint_32p mastering_display_minimum_luminance_scaled_by_10000));
png_uint_32p mastering_display_minimum_luminance_scaled_by_10000))
#endif

#ifdef PNG_mDCV_SUPPORTED
Expand All @@ -2108,7 +2108,7 @@ PNG_FP_EXPORT(258, void, png_set_mDCV, (png_const_structrp png_ptr,
double green_y, double blue_x, double blue_y,
/* Mastering display luminance in cd/m2 (nits). */
double mastering_display_maximum_luminance,
double mastering_display_minimum_luminance));
double mastering_display_minimum_luminance))

PNG_FIXED_EXPORT(259, void, png_set_mDCV_fixed, (png_const_structrp png_ptr,
png_inforp info_ptr,
Expand All @@ -2123,7 +2123,7 @@ PNG_FIXED_EXPORT(259, void, png_set_mDCV_fixed, (png_const_structrp png_ptr,
* must be zero.
*/
png_uint_32 mastering_display_maximum_luminance_scaled_by_10000,
png_uint_32 mastering_display_minimum_luminance_scaled_by_10000));
png_uint_32 mastering_display_minimum_luminance_scaled_by_10000))
#endif

#ifdef PNG_oFFs_SUPPORTED
Expand Down

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