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Remove top-level const from function-scope variables

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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
This commit is contained in:
Cosmin Truta
2018-08-18 22:47:16 -04:00
parent 1ef8882814
commit ceb327789b
22 changed files with 196 additions and 205 deletions
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24
pngread.c
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@@ -1758,9 +1758,9 @@ png_create_colormap_entry(png_image_read_control *display,
png_uint_32 alpha, int encoding)
{
png_imagep image = display->image;
const int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
int output_encoding = (image->format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
const int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
int convert_to_Y = (image->format & PNG_FORMAT_FLAG_COLOR) == 0 &&
(red != green || green != blue);
if (ip > 255)
@@ -1869,13 +1869,13 @@ png_create_colormap_entry(png_image_read_control *display,
/* Store the value. */
{
# ifdef PNG_FORMAT_AFIRST_SUPPORTED
const int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
int afirst = (image->format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
(image->format & PNG_FORMAT_FLAG_ALPHA) != 0;
# else
# define afirst 0
# endif
# ifdef PNG_FORMAT_BGR_SUPPORTED
const int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
int bgr = (image->format & PNG_FORMAT_FLAG_BGR) != 0 ? 2 : 0;
# else
# define bgr 0
# endif
@@ -2085,11 +2085,11 @@ png_image_read_colormap(png_voidp argument)
{
png_image_read_control *display =
png_voidcast(png_image_read_control*, argument);
const png_imagep image = display->image;
png_imagep image = display->image;
const png_structrp png_ptr = image->opaque->png_ptr;
const png_uint_32 output_format = image->format;
const int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
png_structrp png_ptr = image->opaque->png_ptr;
png_uint_32 output_format = image->format;
int output_encoding = (output_format & PNG_FORMAT_FLAG_LINEAR) != 0 ?
P_LINEAR : P_sRGB;
unsigned int cmap_entries;
@@ -2802,7 +2802,7 @@ png_image_read_colormap(png_voidp argument)
unsigned int num_trans = png_ptr->num_trans;
png_const_bytep trans = num_trans > 0 ? png_ptr->trans_alpha : NULL;
png_const_colorp colormap = png_ptr->palette;
const int do_background = trans != NULL &&
int do_background = trans != NULL &&
(output_format & PNG_FORMAT_FLAG_ALPHA) == 0;
unsigned int i;
@@ -3946,7 +3946,7 @@ png_image_read_direct(png_voidp argument)
*/
if (linear != 0)
{
const png_uint_16 le = 0x0001;
png_uint_16 le = 0x0001;
if ((*(png_const_bytep) & le) != 0)
png_set_swap(png_ptr);
@@ -4108,7 +4108,7 @@ png_image_finish_read(png_imagep image, png_const_colorp background,
* original PNG format because it may not occur in the output PNG format
* and libpng deals with the issues of reading the original.
*/
const unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);
/* The following checks just the 'row_stride' calculation to ensure it
* fits in a signed 32-bit value. Because channels/components can be
@@ -4119,7 +4119,7 @@ png_image_finish_read(png_imagep image, png_const_colorp background,
if (image->width <= 0x7fffffffU/channels) /* no overflow */
{
png_uint_32 check;
const png_uint_32 png_row_stride = image->width * channels;
png_uint_32 png_row_stride = image->width * channels;
if (row_stride == 0)
row_stride = (png_int_32)/*SAFE*/png_row_stride;