Remove top-level const from function-scope variables
As per the const correctness rules, top-level const-ness of data
in automatic scopes does not propagate outside of these scopes
(unlike const-ness at lower levels, such as pointers to const data).
Previously, const was used liberally, but inconsistently across the
libpng codebase. Using const wherever applicable is not incorrect.
However, _consistent_ use of const is difficult to maintain in such
conditions.
In conclusion, we shall continue to use const only where doing so is
strictly necessary:
1. If a function guarantees that it will not modify an argument
passed by pointer, the corresponding function parameter should be
a pointer-to-const (const T *).
2. Static data should not be modified, therefore it should be const.
Reference:
Google C++ Style Guide
https://google.github.io/styleguide/cppguide.html#Use_of_const
diff --git a/pngrtran.c b/pngrtran.c
index e61be87..6b9b720 100644
--- a/pngrtran.c
+++ b/pngrtran.c
@@ -2986,7 +2986,6 @@
*/
static int
png_do_rgb_to_gray(png_structrp png_ptr, png_row_infop row_info, png_bytep row)
-
{
int rgb_error = 0;
@@ -2995,12 +2994,11 @@
if ((row_info->color_type & PNG_COLOR_MASK_PALETTE) == 0 &&
(row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
{
- const png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
- const png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
- const png_uint_32 bc = 32768 - rc - gc;
- const png_uint_32 row_width = row_info->width;
- const int have_alpha =
- (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
+ png_uint_32 rc = png_ptr->rgb_to_gray_red_coeff;
+ png_uint_32 gc = png_ptr->rgb_to_gray_green_coeff;
+ png_uint_32 bc = 32768 - rc - gc;
+ png_uint_32 row_width = row_info->width;
+ int have_alpha = (row_info->color_type & PNG_COLOR_MASK_ALPHA) != 0;
if (row_info->bit_depth == 8)
{
@@ -4143,12 +4141,11 @@
{
if (row_info->bit_depth == 8)
{
- const png_bytep table = png_ptr->gamma_from_1;
+ png_bytep table = png_ptr->gamma_from_1;
if (table != NULL)
{
- const int step =
- (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
+ int step = (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 4 : 2;
/* The alpha channel is the last component: */
row += step - 1;
@@ -4162,13 +4159,12 @@
else if (row_info->bit_depth == 16)
{
- const png_uint_16pp table = png_ptr->gamma_16_from_1;
- const int gamma_shift = png_ptr->gamma_shift;
+ png_uint_16pp table = png_ptr->gamma_16_from_1;
+ int gamma_shift = png_ptr->gamma_shift;
if (table != NULL)
{
- const int step =
- (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
+ int step = (row_info->color_type & PNG_COLOR_MASK_COLOR) ? 8 : 4;
/* The alpha channel is the last component: */
row += step - 2;