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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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4
pngerror.c
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@@ -885,7 +885,7 @@ PNG_FUNCTION(void /* PRIVATE */, (PNGCBAPI
png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
PNG_NORETURN)
{
const png_const_structrp png_ptr = png_nonconst_ptr;
png_const_structrp png_ptr = png_nonconst_ptr;
png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
/* An error is always logged here, overwriting anything (typically a warning)
@@ -920,7 +920,7 @@ png_safe_error),(png_structp png_nonconst_ptr, png_const_charp error_message),
void /* PRIVATE */ PNGCBAPI
png_safe_warning(png_structp png_nonconst_ptr, png_const_charp warning_message)
{
const png_const_structrp png_ptr = png_nonconst_ptr;
png_const_structrp png_ptr = png_nonconst_ptr;
png_imagep image = png_voidcast(png_imagep, png_ptr->error_ptr);
/* A warning is only logged if there is no prior warning or error. */